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• How to add multiple condition cases inside Switch method?

  - by shutup

  Is there a way to include multiple cases inside a switch method in php?

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• Why can't initialize the static member in a class in the body or in the header file?

  - by skydoor

  Could any body offer me any reason about that? If we do it like that, what's the outcome? Compile error?

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• C# 4 Named Parameters for Overload Resolution

  - by Steve Michelotti

  C# 4 is getting a new feature called named parameters. Although this is a stand-alone feature, it is often used in conjunction with optional parameters. Last week when I was giving a presentation on C# 4, I got a question on a scenario regarding overload resolution that I had not considered before which yielded interesting results. Before I describe the scenario, a little background first. Named parameters is a well documented feature that works like this: suppose you have a method defined like this: 1: void DoWork(int num, string message = "Hello") 2: { 3: Console.WriteLine("Inside DoWork() - num: {0}, message: {1}", num, message); 4: } This enables you to call the method with any of these: 1: DoWork(21); 2: DoWork(num: 21); 3: DoWork(21, "abc"); 4: DoWork(num: 21, message: "abc"); and the corresponding results will be: Inside DoWork() - num: 21, message: Hello Inside DoWork() - num: 21, message: Hello Inside DoWork() - num: 21, message: abc Inside DoWork() - num: 21, message: abc This is all pretty straight forward and well-documented. What is slightly more interesting is how resolution is handled with method overloads. Suppose we had a second overload for DoWork() that looked like this: 1: void DoWork(object num) 2: { 3: Console.WriteLine("Inside second overload: " + num); 4: } The first rule applied for method overload resolution in this case is that it looks for the most strongly-type match first.  Hence, since the second overload has System.Object as the parameter rather than Int32, this second overload will never be called for any of the 4 method calls above.  But suppose the method overload looked like this: 1: void DoWork(int num) 2: { 3: Console.WriteLine("Inside second overload: " + num); 4: } In this case, both overloads have the first parameter as Int32 so they both fulfill the first rule equally.  In this case the overload with the optional parameters will be ignored if the parameters are not specified. Therefore, the same 4 method calls from above would result in: Inside second overload: 21 Inside second overload: 21 Inside DoWork() - num: 21, message: abc Inside DoWork() - num: 21, message: abc Even all this is pretty well documented. However, we can now consider the very interesting scenario I was presented with. The question was what happens if you change the parameter name in one of the overloads.  For example, what happens if you change the parameter *name* for the second overload like this: 1: void DoWork(int num2) 2: { 3: Console.WriteLine("Inside second overload: " + num2); 4: } In this case, the first 2 method calls will yield *different* results: 1: DoWork(21); 2: DoWork(num: 21); results in: Inside second overload: 21 Inside DoWork() - num: 21, message: Hello We know the first method call will go to the second overload because of normal method overload resolution rules which ignore the optional parameters.  But for the second call, even though all the same rules apply, the compiler will allow you to specify a named parameter which, in effect, overrides the typical rules and directs the call to the first overload. Keep in mind this would only work if the method overloads had different parameter names for the same types (which in itself is weird). But it is a situation I had not considered before and it is one in which you should be aware of the rules that the C# 4 compiler applies.

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• Anatomy of a .NET Assembly - Signature encodings

  - by Simon Cooper

  If you've just joined this series, I highly recommend you read the previous posts in this series, starting here, or at least these posts, covering the CLR metadata tables. Before we look at custom attribute encoding, we first need to have a brief look at how signatures are encoded in an assembly in general. Signature types There are several types of signatures in an assembly, all of which share a common base representation, and are all stored as binary blobs in the #Blob heap, referenced by an offset from various metadata tables. The types of signatures are: Method definition and method reference signatures. Field signatures Property signatures Method local variables. These are referenced from the StandAloneSig table, which is then referenced by method body headers. Generic type specifications. These represent a particular instantiation of a generic type. Generic method specifications. Similarly, these represent a particular instantiation of a generic method. All these signatures share the same underlying mechanism to represent a type Representing a type All metadata signatures are based around the ELEMENT_TYPE structure. This assigns a number to each 'built-in' type in the framework; for example, Uint16 is 0x07, String is 0x0e, and Object is 0x1c. Byte codes are also used to indicate SzArrays, multi-dimensional arrays, custom types, and generic type and method variables. However, these require some further information. Firstly, custom types (ie not one of the built-in types). These require you to specify the 4-byte TypeDefOrRef coded token after the CLASS (0x12) or VALUETYPE (0x11) element type. This 4-byte value is stored in a compressed format before being written out to disk (for more excruciating details, you can refer to the CLI specification). SzArrays simply have the array item type after the SZARRAY byte (0x1d). Multidimensional arrays follow the ARRAY element type with a series of compressed integers indicating the number of dimensions, and the size and lower bound of each dimension. Generic variables are simply followed by the index of the generic variable they refer to. There are other additions as well, for example, a specific byte value indicates a method parameter passed by reference (BYREF), and other values indicating custom modifiers. Some examples... To demonstrate, here's a few examples and what the resulting blobs in the #Blob heap will look like. Each name in capitals corresponds to a particular byte value in the ELEMENT_TYPE or CALLCONV structure, and coded tokens to custom types are represented by the type name in curly brackets. A simple field: int intField; FIELD I4 A field of an array of a generic type parameter (assuming T is the first generic parameter of the containing type): T[] genArrayField FIELD SZARRAY VAR 0 An instance method signature (note how the number of parameters does not include the return type): instance string MyMethod(MyType, int&, bool[][]); HASTHIS DEFAULT 3 STRING CLASS {MyType} BYREF I4 SZARRAY SZARRAY BOOLEAN A generic type instantiation: MyGenericType<MyType, MyStruct> GENERICINST CLASS {MyGenericType} 2 CLASS {MyType} VALUETYPE {MyStruct} For more complicated examples, in the following C# type declaration: GenericType<T> : GenericBaseType<object[], T, GenericType<T>> { ... } the Extends field of the TypeDef for GenericType will point to a TypeSpec with the following blob: GENERICINST CLASS {GenericBaseType} 3 SZARRAY OBJECT VAR 0 GENERICINST CLASS {GenericType} 1 VAR 0 And a static generic method signature (generic parameters on types are referenced using VAR, generic parameters on methods using MVAR): TResult[] GenericMethod<TInput, TResult>( TInput, System.Converter<TInput, TOutput>); GENERIC 2 2 SZARRAY MVAR 1 MVAR 0 GENERICINST CLASS {System.Converter} 2 MVAR 0 MVAR 1 As you can see, complicated signatures are recursively built up out of quite simple building blocks to represent all the possible variations in a .NET assembly. Now we've looked at the basics of normal method signatures, in my next post I'll look at custom attribute application signatures, and how they are different to normal signatures.

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• TFS API Add Favorites programmatically

  - by Tarun Arora

  01 – What are we trying to achieve? In this blog post I’ll be showing you how to add work item queries as favorites, it is also possible to use the same technique to add build definition as favorites. Once a shared query or build definition has been added as favorite it will show up on the team web access.  In this blog post I’ll be showing you a work around in the absence of a proper API how you can add queries to team favorites. 02 – Disclaimer There is no official API for adding favorites programmatically. In the work around below I am using the Identity service to store this data in a property bag which is used during display of favorites on the team web site. This uses an internal data structure that could change over time, there is no guarantee about the key names or content of the values. What is shown below is a workaround for a missing API. 03 – Concept There is no direct API support for favorites, but you could work around it using the identity service in TFS.  Favorites are stored in the property bag associated with the TeamFoundationIdentity (either the ‘team’ identity or the users identity depending on if these are ‘team’ or ‘my’ favorites).  The data is stored as json in the property bag of the identity, the key being prefixed by ‘Microsoft.TeamFoundation.Framework.Server.IdentityFavorites’. References - Microsoft.TeamFoundation.WorkItemTracking.Client - using Microsoft.TeamFoundation.Client; - using Microsoft.TeamFoundation.Framework.Client; - using Microsoft.TeamFoundation.Framework.Common; - using Microsoft.TeamFoundation.ProcessConfiguration.Client; - using Microsoft.TeamFoundation.Server; - using Microsoft.TeamFoundation.WorkItemTracking.Client; Services - IIdentityManagementService2 - TfsTeamService - WorkItemStore 04 – Solution Lets start by connecting to TFS programmatically // Create an instance of the services to be used during the program private static TfsTeamProjectCollection _tfs; private static ProjectInfo _selectedTeamProject; private static WorkItemStore _wis; private static TfsTeamService _tts; private static TeamSettingsConfigurationService _teamConfig; private static IIdentityManagementService2 _ids; // Connect to TFS programmatically public static bool ConnectToTfs() { var isSelected = false; var tfsPp = new TeamProjectPicker(TeamProjectPickerMode.SingleProject, false); tfsPp.ShowDialog(); _tfs = tfsPp.SelectedTeamProjectCollection; if (tfsPp.SelectedProjects.Any()) { _selectedTeamProject = tfsPp.SelectedProjects[0]; isSelected = true; } return isSelected; } Lets get all the work item queries from the selected team project static readonly Dictionary<string, string> QueryAndGuid = new Dictionary<string, string>(); // Get all queries and query guid in the selected team project private static void GetQueryGuidList(IEnumerable<QueryItem> query) { foreach (QueryItem subQuery in query) { if (subQuery.GetType() == typeof(QueryFolder)) GetQueryGuidList((QueryFolder)subQuery); else { QueryAndGuid.Add(subQuery.Name, subQuery.Id.ToString()); } } }   Pass the name of a valid Team in your team project and a name of a valid query in your team project. The team details will be extracted using the team name and query GUID will be extracted using the query name. These details will be used to construct the key and value that will be passed to the SetProperty method in the Identity service.           Key           “Microsoft.TeamFoundation.Framework.Server.IdentityFavorites..<TeamProjectURI>.<TeamId>.WorkItemTracking.Queries.<newGuid1>”           Value           "{"data":"<QueryGuid>","id":"<NewGuid1>","name":"<QueryKey>","type":"Microsoft.TeamFoundation.WorkItemTracking.QueryItem”}"           // Configure a Work Item Query for the given team private static void ConfigureTeamFavorites(string teamName, string queryName) { _ids = _tfs.GetService<IIdentityManagementService2>(); var g = Guid.NewGuid(); var guid = string.Empty; var teamDetail = _tts.QueryTeams(_selectedTeamProject.Uri).FirstOrDefault(t => t.Name == teamName); foreach (var q in QueryAndGuid.Where(q => q.Key == queryName)) { guid = q.Value; } if(guid == string.Empty) { Console.WriteLine("Query '{0}' - Not found!", queryName); return; } var key = string.Format( "Microsoft.TeamFoundation.Framework.Server.IdentityFavorites..{0}.{1}.WorkItemTracking.Queries{2}", new Uri(_selectedTeamProject.Uri).Segments.LastOrDefault(), teamDetail.Identity.TeamFoundationId, g); var value = string.Format( @"{0}""data"":""{1}"",""id"":""{2}"",""name"":""{3}"",""type"":""Microsoft.TeamFoundation.WorkItemTracking.QueryItem""{4}", "{", guid, g, QueryAndGuid.FirstOrDefault(q => q.Value==guid).Key, "}"); teamDetail.Identity.SetProperty(IdentityPropertyScope.Local, key, value); _ids.UpdateExtendedProperties(teamDetail.Identity); Console.WriteLine("{0}Added Query '{1}' as Favorite", Environment.NewLine, queryName); }   If you have any questions or suggestions leave a comment. Enjoy!

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• Extended FindWindow

  - by João Angelo

  The Win32 API provides the FindWindow function that supports finding top-level windows by their class name and/or title. However, the title search does not work if you are trying to match partial text at the middle or the end of the full window title. You can however implement support for these extended search features by using another set of Win32 API like EnumWindows and GetWindowText. A possible implementation follows: using System; using System.Collections.Generic; using System.Linq; using System.Runtime.InteropServices; using System.Text; public class WindowInfo { private IntPtr handle; private string className; internal WindowInfo(IntPtr handle, string title) { if (handle == IntPtr.Zero) throw new ArgumentException("Invalid handle.", "handle"); this.Handle = handle; this.Title = title ?? string.Empty; } public string Title { get; private set; } public string ClassName { get { if (className == null) { className = GetWindowClassNameByHandle(this.Handle); } return className; } } public IntPtr Handle { get { if (!NativeMethods.IsWindow(this.handle)) throw new InvalidOperationException("The handle is no longer valid."); return this.handle; } private set { this.handle = value; } } public static WindowInfo[] EnumerateWindows() { var windows = new List<WindowInfo>(); NativeMethods.EnumWindowsProcessor processor = (hwnd, lParam) => { windows.Add(new WindowInfo(hwnd, GetWindowTextByHandle(hwnd))); return true; }; bool succeeded = NativeMethods.EnumWindows(processor, IntPtr.Zero); if (!succeeded) return new WindowInfo[] { }; return windows.ToArray(); } public static WindowInfo FindWindow(Predicate<WindowInfo> predicate) { WindowInfo target = null; NativeMethods.EnumWindowsProcessor processor = (hwnd, lParam) => { var current = new WindowInfo(hwnd, GetWindowTextByHandle(hwnd)); if (predicate(current)) { target = current; return false; } return true; }; NativeMethods.EnumWindows(processor, IntPtr.Zero); return target; } private static string GetWindowTextByHandle(IntPtr handle) { if (handle == IntPtr.Zero) throw new ArgumentException("Invalid handle.", "handle"); int length = NativeMethods.GetWindowTextLength(handle); if (length == 0) return string.Empty; var buffer = new StringBuilder(length + 1); NativeMethods.GetWindowText(handle, buffer, buffer.Capacity); return buffer.ToString(); } private static string GetWindowClassNameByHandle(IntPtr handle) { if (handle == IntPtr.Zero) throw new ArgumentException("Invalid handle.", "handle"); const int WindowClassNameMaxLength = 256; var buffer = new StringBuilder(WindowClassNameMaxLength); NativeMethods.GetClassName(handle, buffer, buffer.Capacity); return buffer.ToString(); } } internal class NativeMethods { public delegate bool EnumWindowsProcessor(IntPtr hwnd, IntPtr lParam); [DllImport("user32.dll")] [return: MarshalAs(UnmanagedType.Bool)] public static extern bool EnumWindows( EnumWindowsProcessor lpEnumFunc, IntPtr lParam); [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)] public static extern int GetWindowText( IntPtr hWnd, StringBuilder lpString, int nMaxCount); [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)] public static extern int GetWindowTextLength(IntPtr hWnd); [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)] public static extern int GetClassName( IntPtr hWnd, StringBuilder lpClassName, int nMaxCount); [DllImport("user32.dll")] [return: MarshalAs(UnmanagedType.Bool)] public static extern bool IsWindow(IntPtr hWnd); } The access to the windows handle is preceded by a sanity check to assert if it’s still valid, but if you are dealing with windows out of your control then the window can be destroyed right after the check so it’s not guaranteed that you’ll get a valid handle. Finally, to wrap this up a usage, example: static void Main(string[] args) { var w = WindowInfo.FindWindow(wi => wi.Title.Contains("Test.docx")); if (w != null) { Console.Write(w.Title); } }

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• Get coordinates of arraylist

  - by opiop65

  Here's my map class: public class map{ public static final int CLEAR = 0; public static final ArrayList<Integer> STONE = new ArrayList<Integer>(); public static final int GRASS = 2; public static final int DIRT = 3; public static final int WIDTH = 32; public static final int HEIGHT = 24; public static final int TILE_SIZE = 25; // static int[][] map = new int[WIDTH][HEIGHT]; ArrayList<ArrayList<Integer>> map = new ArrayList<ArrayList<Integer>>(WIDTH * HEIGHT); enum tiles { air, grass, stone, dirt } Image air, grass, stone, dirt; Random rand = new Random(); public Map() { /* default map */ /*for(int y = 0; y < WIDTH; y++){ map[y][y] = (rand.nextInt(2)); System.out.println(map[y][y]); }*/ /*for (int y = 18; y < HEIGHT; y++) { for (int x = 0; x < WIDTH; x++) { map[x][y] = STONE; } } for (int y = 18; y < 19; y++) { for (int x = 0; x < WIDTH; x++) { map[x][y] = GRASS; } } for (int y = 19; y < 20; y++) { for (int x = 0; x < WIDTH; x++) { map[x][y] = DIRT; } }*/ for (int y = 0; y < HEIGHT; y++) { for(int x = 0; x < WIDTH; x++){ map.set(x * WIDTH + y, STONE); } } try { init(null, null); } catch (SlickException e) { e.printStackTrace(); } render(null, null, null); } public void init(GameContainer gc, StateBasedGame sbg) throws SlickException { air = new Image("res/air.png"); grass = new Image("res/grass.png"); stone = new Image("res/stone.png"); dirt = new Image("res/dirt.png"); } public void render(GameContainer gc, StateBasedGame sbg, Graphics g) { for (int x = 0; x < WIDTH; x++) { for (int y = 0; y < HEIGHT; y++) { switch (map.get(x * WIDTH + y)) { case CLEAR: air.draw(x * TILE_SIZE, y * TILE_SIZE, TILE_SIZE, TILE_SIZE); break; case STONE: stone.draw(x * TILE_SIZE, y * TILE_SIZE, TILE_SIZE, TILE_SIZE); break; case GRASS: grass.draw(x * TILE_SIZE, y * TILE_SIZE, TILE_SIZE, TILE_SIZE); break; case DIRT: dirt.draw(x * TILE_SIZE, y * TILE_SIZE, TILE_SIZE, TILE_SIZE); break; } } } } public static boolean blocked(float x, float y) { return map[(int) x][(int) y] == STONE; } public static Rectangle blockBounds(int x, int y) { return (new Rectangle(x, y, TILE_SIZE, TILE_SIZE)); } } Specifically I am looking at this: for (int x = 0; x < WIDTH; x++) { for (int y = 0; y < HEIGHT; y++) { switch (map.get(x * WIDTH + y).intValue()) { case CLEAR: air.draw(x * TILE_SIZE, y * TILE_SIZE, TILE_SIZE, TILE_SIZE); break; case STONE: stone.draw(x * TILE_SIZE, y * TILE_SIZE, TILE_SIZE, TILE_SIZE); break; case GRASS: grass.draw(x * TILE_SIZE, y * TILE_SIZE, TILE_SIZE, TILE_SIZE); break; case DIRT: dirt.draw(x * TILE_SIZE, y * TILE_SIZE, TILE_SIZE, TILE_SIZE); break; } } } How can I access the coordinates of my arraylist map and then draw the tiles to the screen? Thanks!

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• Resolving a collision between point and moving line

  - by Conundrumer

  I am designing a 2d physics engine that uses Verlet integration for moving points (velocities mentioned below can be derived), constraints to represent moving line segments, and continuous collision detection to resolve collisions between moving points and static lines, and collisions between moving/static points and moving lines. I already know how to calculate the Time of Impact for both types of collision events, and how to resolve moving point static line collisions. However, I can't figure out how to resolve moving/static point moving line collisions. Here are the initial conditions in a point and moving line collision event. We have a line segment joined by two points, A and B. At this instant, point P is touching/colliding with line AB. These points have unit mass and some might have an initial velocity, unless point P is static. The line is massless and has no explicit rotational component, since points A and B could freely move around, extending or contracting the line as a result (which will be fixed later by the constraint solver). Collision is inelastic. What are the final velocities of the points after collision?

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• Why do I get an exception when playing multiple sound instances?

  - by Boreal

  Right now, I'm adding a rudimentary sound engine to my game. So far, I am able to load in a WAV file and play it once, then free up the memory when I close the game. However, the game crashes with a nice ArgumentOutOfBoundsException when I try to play another sound instance. Specified argument was out of the range of valid values. Parameter name: readLength I'm following this tutorial pretty much exactly, but I still keep getting the aforementioned error. Here's my sound-related code. /// <summary> /// Manages all sound instances. /// </summary> public static class Audio { static XAudio2 device; static MasteringVoice master; static List<SoundInstance> instances; /// <summary> /// The XAudio2 device. /// </summary> internal static XAudio2 Device { get { return device; } } /// <summary> /// Initializes the audio device and master track. /// </summary> internal static void Initialize() { device = new XAudio2(); master = new MasteringVoice(device); instances = new List<SoundInstance>(); } /// <summary> /// Releases all XA2 resources. /// </summary> internal static void Shutdown() { foreach(SoundInstance i in instances) i.Dispose(); master.Dispose(); device.Dispose(); } /// <summary> /// Registers a sound instance with the system. /// </summary> /// <param name="instance">Sound instance</param> internal static void AddInstance(SoundInstance instance) { instances.Add(instance); } /// <summary> /// Disposes any sound instance that has stopped playing. /// </summary> internal static void Update() { List<SoundInstance> temp = new List<SoundInstance>(instances); foreach(SoundInstance i in temp) if(!i.Playing) { i.Dispose(); instances.Remove(i); } } } /// <summary> /// Loads sounds from various files. /// </summary> internal class SoundLoader { /// <summary> /// Loads a .wav sound file. /// </summary> /// <param name="format">The decoded format will be sent here</param> /// <param name="buffer">The data will be sent here</param> /// <param name="soundName">The path to the WAV file</param> internal static void LoadWAV(out WaveFormat format, out AudioBuffer buffer, string soundName) { WaveStream wave = new WaveStream(soundName); format = wave.Format; buffer = new AudioBuffer(); buffer.AudioData = wave; buffer.AudioBytes = (int)wave.Length; buffer.Flags = BufferFlags.EndOfStream; } } /// <summary> /// Manages the data for a single sound. /// </summary> public class Sound : IAsset { WaveFormat format; AudioBuffer buffer; /// <summary> /// Loads a sound from a file. /// </summary> /// <param name="soundName">The path to the sound file</param> /// <returns>Whether the sound loaded successfully</returns> public bool Load(string soundName) { if(soundName.EndsWith(".wav")) SoundLoader.LoadWAV(out format, out buffer, soundName); else return false; return true; } /// <summary> /// Plays the sound. /// </summary> public void Play() { Audio.AddInstance(new SoundInstance(format, buffer)); } /// <summary> /// Unloads the sound from memory. /// </summary> public void Unload() { buffer.Dispose(); } } /// <summary> /// Manages a single sound instance. /// </summary> public class SoundInstance { SourceVoice source; bool playing; /// <summary> /// Whether the sound is currently playing. /// </summary> public bool Playing { get { return playing; } } /// <summary> /// Starts a new instance of a sound. /// </summary> /// <param name="format">Format of the sound</param> /// <param name="buffer">Buffer holding sound data</param> internal SoundInstance(WaveFormat format, AudioBuffer buffer) { source = new SourceVoice(Audio.Device, format); source.BufferEnd += (s, e) => playing = false; source.Start(); source.SubmitSourceBuffer(buffer); // THIS IS WHERE THE EXCEPTION IS THROWN playing = true; } /// <summary> /// Releases memory used by the instance. /// </summary> internal void Dispose() { source.Dispose(); } } The exception occurs on line 156 when I am playing the sound: source.SubmitSourceBuffer(buffer);

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• Fixing a collision detection bug in Slick2D

  - by Jesse Prescott

  My game has a bug with collision detection. If you go against the wall and tap forward/back sometimes the game thinks the speed you travelled at is 0 and the game doesn't know how to get you out of the wall. My collision detection works by getting the speed you hit the wall at and if it is positive it moves you back, if it is negative it moves you forward. It might help if you download it: https://rapidshare.com/files/1550046269/game.zip Sorry if I explained badly, it's hard to explain. float maxSpeed = 0.3f; float minSpeed = -0.2f; float acceleration = 0.002f; float deacceleration = 0.001f; float slowdownSpeed = 0.002f; float rotateSpeed = 0.08f; static float currentSpeed = 0; boolean up = false; boolean down = false; boolean noKey = false; static float rotate = 0; //Image effect system static String locationCarNormal; static String locationCarFront; static String locationCarBack; static String locationCarBoth; static boolean carFront = false; static boolean carBack = false; static String imageRef; boolean collision = false; public ComponentPlayerMovement(String id, String ScarNormal, String ScarFront, String ScarBack, String ScarBoth) { this.id = id; playerBody = new Rectangle(900/2-16, 700/2-16, 32, 32); locationCarNormal = ScarNormal; locationCarFront = ScarFront; locationCarBack = ScarBack; locationCarBoth = ScarBoth; imageRef = locationCarNormal; } @Override public void update(GameContainer gc, StateBasedGame sbg, int delta) throws SlickException { Input input = gc.getInput(); playerBody.transform(Transform.createRotateTransform(2)); float hip = currentSpeed * delta; float unstuckspeed = 0.05f * delta; if(carBack && !carFront) { imageRef = locationCarBack; ComponentImageRender.updateImage(); } else if(carFront && !carBack) { imageRef = locationCarFront; ComponentImageRender.updateImage(); } else if(carFront && carBack) { imageRef = locationCarBoth; ComponentImageRender.updateImage(); } if(input.isKeyDown(Input.KEY_RIGHT)) { rotate += rotateSpeed * delta; owner.setRotation(rotate); } if(input.isKeyDown(Input.KEY_LEFT)) { rotate -= rotateSpeed * delta; owner.setRotation(rotate); } if(input.isKeyDown(Input.KEY_UP)) { if(!collision) { up = true; noKey = false; if(currentSpeed < maxSpeed) { currentSpeed += acceleration; } MapCoordStorage.mapX += hip * Math.sin(Math.toRadians(rotate)); MapCoordStorage.mapY -= hip * Math.cos(Math.toRadians(rotate)); } else { currentSpeed = 1; } } else if(input.isKeyDown(Input.KEY_DOWN) && !collision) { down = true; noKey = false; if(currentSpeed > minSpeed) { currentSpeed -= slowdownSpeed; } MapCoordStorage.mapX += hip * Math.sin(Math.toRadians(rotate)); MapCoordStorage.mapY -= hip * Math.cos(Math.toRadians(rotate)); } else { noKey = true; if(currentSpeed > 0) { currentSpeed -= deacceleration; } else if(currentSpeed < 0) { currentSpeed += acceleration; } MapCoordStorage.mapX += hip * Math.sin(Math.toRadians(rotate)); MapCoordStorage.mapY -= hip * Math.cos(Math.toRadians(rotate)); } if(entityCollisionWith()) { collision = true; if(currentSpeed > 0 || up) { up = true; currentSpeed = 0; carFront = true; MapCoordStorage.mapX += unstuckspeed * Math.sin(Math.toRadians(rotate-180)); MapCoordStorage.mapY -= unstuckspeed * Math.cos(Math.toRadians(rotate-180)); } else if(currentSpeed < 0 || down) { down = true; currentSpeed = 0; carBack = true; MapCoordStorage.mapX += unstuckspeed * Math.sin(Math.toRadians(rotate)); MapCoordStorage.mapY -= unstuckspeed * Math.cos(Math.toRadians(rotate)); } else { currentSpeed = 0; } } else { collision = false; up = false; down = false; } if(currentSpeed >= -0.01f && currentSpeed <= 0.01f && noKey && !collision) { currentSpeed = 0; } } public static boolean entityCollisionWith() throws SlickException { for (int i = 0; i < BlockMap.entities.size(); i++) { Block entity1 = (Block) BlockMap.entities.get(i); if (playerBody.intersects(entity1.poly)) { return true; } } return false; } }

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• Traversing Java Object Arrays [migrated]

  - by Sundi

  Please Help. Program does not read Array rentBooks[] in the for() loop this option is selected when choosing option 2 then option 4 in the menu The Array reads perfectly when reading the items after the setBook() Method import java.io.File; import java.io.FileNotFoundException; import java.util.Scanner; import java.io.*; import java.util.Locale; import java.text.SimpleDateFormat ; class Library { protected static String Author; protected static String Title; SimpleDateFormat PublicationDate; int itemCode; int available = 1; } class Book extends Library { protected static String PublisherName; protected static String Edition; static Book[] rentBooks = new Book[5]; //Book[] rentBooks = new Book[5]; int count = 0; public Book() { String start= "start"; showBook.main(anza); } public void setBook( String Auth, String Titl, String PublishName) { this.Author = Auth; this.Title = Titl; this.PublisherName = PublishName; } public void getBook() { //System.out.println("*************BOOKS*************************"); System.out.println( "\n\nThe Author of the first Book is "+ this.Author ); System.out.println( "The Title of the book is "+ this.Title); System.out.println( "The Publisher of the book is "+ this.PublisherName ); // System.out.println( "The Edition of the book is "+ Edition ); } } class showBook{ static Book[] rentBooks = new Book[5]; static Book[] rentBooks2 = new Book[5]; static int a,b; //for ( a=0; a < 5; a++ ) //rentBooks2[a] = new Book(); public static void main(String[] args) { File file = new File("Book2.txt"); //Book libraryBooks = new Book(); int j; //initialise Array Class Objects for( j = 0; j < 5; j++) { rentBooks[j] = new Book(); } int i = 0; try{ Scanner scanner = new Scanner(file); scanner.useDelimiter(","); String loan=""; int loan2; while( scanner.hasNextLine()) { //Should the Books be Stored in An Array? // At the moment you have separate objects stored in unknown location String Author = scanner.next(); String Title = scanner.next(); String PublisherName = scanner.next(); if ( i < 4) { System.out.println(i); rentBooks[i].setBook(Author, Title, PublisherName); rentBooks[i].getBook(); // MEMBERS SHOWN i++; } public class readBook4{ public static void main(String[] args) { int number =0; System.out.println( "Please select one of the choices below " ); System.out.println( "Select option 1 to list all items in the library "); System.out.println( "Select option 2 to list the items by category"); System.out.println( "Select option 3 to choose item available in the library "); System.out.println( "Select option 7 to exit " ); InputStreamReader isr = new InputStreamReader( System.in); BufferedReader buffer = new BufferedReader( isr); String input = ""; try { input = buffer.readLine(); number = Integer.parseInt(input); //int number = Integer.parseInt( Edition); if ( number == 1 ) { System.out.println( " \nThanks you are reading "+ input); //showStudent.main(args); showPeriodical.main(args); showDVD.main(args); // showBook.main(args); } if ( number == 2 ) { //jht.cls(); int number2; System.out.println( "Please select one of the choices below " ); System.out.println( "Select option 4 to list Books only "); System.out.println( "Select option 5 to list the Periodicals only"); System.out.println( "Select option 6 to list DVDs only"); InputStreamReader isr2 = new InputStreamReader(System.in); BufferedReader buffer2 = new BufferedReader(isr2); String input2 = ""; try { input2 = buffer2.readLine(); buffer.close(); } catch(IOException e) { System.out.println("An input error has occured"); } //System.out.println("Thanks, you are reading" + input2); number2 = Integer.parseInt(input2); if ( number2 == 4 ) { showBook.main(args); } if ( number2 == 5 ) { showPeriodical.main(args); } if ( number2 == 6 ) { showDVD.main(args); } // readBook4.main(args); } if( number == 3 ) { //showBook.main(args); showBook.availableBooks(); showDVD.availableDVD(); showPeriodical.availablePeriodical(); } if ( number == 7 ) { showStudent.main(args); } buffer.close(); } catch( IOException e ) { System.out.println( " An input error has occured "); } //System.out.println( " \nThanks you are reading "+ input); } } } //buffer.close(); scanner.close(); } catch( FileNotFoundException e) { System.out.println("File not Found"); } for ( i=0; i < 5; i++ ) rentBooks[i].getBook(); //ARRAY NOT SHOWN } }

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• Adding a second table in a database

  - by MB

  Hi everyone. I used the code provided by the NoteExample from the developers doc to create a database. Now I want to add a second table to store different data. I simply "copied" the given code, but when I try to insert into the new table I get an error saying: "0ERROR/Database(370): android.database.sqlite.SQLiteException: no such table: routes: , while compiling: INSERT INTO routes(line, arrival, duration, start) VALUES(?, ?, ?, ?);" Can someone please take quick look at my DbAdapter class and give me a hint or a solution? I really don't see any problem. my code compiles without any errors.. thanks in advance! CODE: import static android.provider.BaseColumns._ID; import android.content.ContentValues; import android.content.Context; import android.database.Cursor; import android.database.SQLException; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; import android.util.Log; public class DbAdapter { public static final String KEY_FROM = "title"; public static final String KEY_TO = "body"; public static final String KEY_ROWID = "_id"; public static final String KEY_START = "start"; public static final String KEY_ARRIVAL = "arrival"; public static final String KEY_LINE = "line"; public static final String KEY_DURATION = "duration"; private static final String DATABASE_NAME = "data"; private static final String DATABASE_NOTESTABLE = "notes"; private static final String DATABASE_ROUTESTABLE = "routes"; private static final String TAG = "DbAdapter"; private DatabaseHelper mDbHelper; private SQLiteDatabase mDb; /** * Database creation sql statement */ private static final String DATABASE_CREATE_NOTES = "create table notes (_id integer primary key autoincrement, " + "title text not null, body text not null)"; private static final String DATABASE_CREATE_ROUTES = "create table routes (_id integer primary key autoincrement, " + "start text not null, arrival text not null, " + "line text not null, duration text not null);"; private static final int DATABASE_VERSION = 2; private final Context mCtx; private static class DatabaseHelper extends SQLiteOpenHelper { DatabaseHelper(Context context) { super(context, DATABASE_NAME, null, DATABASE_VERSION); } @Override public void onCreate(SQLiteDatabase db) { db.execSQL(DATABASE_CREATE_NOTES); Log.d(TAG, "created notes table"); db.execSQL(DATABASE_CREATE_ROUTES); //CREATE LOKALTABLE db.execSQL("CREATE TABLE " + DATABASE_ROUTESTABLE + " " + "(" + _ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " + KEY_START + " TEXT NOT NULL, " + KEY_ARRIVAL + " TEXT NOT NULL, " + KEY_LINE + " TEXT NOT NULL, " + KEY_DURATION + " TEXT NOT NULL"); Log.d(TAG, "created routes table"); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { Log.w(TAG, "Upgrading database from version " + oldVersion + " to " + newVersion + ", which will destroy all old data"); db.execSQL("DROP TABLE IF EXISTS notes"); onCreate(db); } } /** * Constructor - takes the context to allow the database to be * opened/created * * @param ctx the Context within which to work */ public DbAdapter(Context ctx) { this.mCtx = ctx; } /** * Open the notes database. If it cannot be opened, try to create a new * instance of the database. If it cannot be created, throw an exception to * signal the failure * * @return this (self reference, allowing this to be chained in an * initialization call) * @throws SQLException if the database could be neither opened or created */ public DbAdapter open() throws SQLException { mDbHelper = new DatabaseHelper(mCtx); mDb = mDbHelper.getWritableDatabase(); return this; } public void close() { mDbHelper.close(); } /** * Create a new note using the title and body provided. If the note is * successfully created return the new rowId for that note, otherwise return * a -1 to indicate failure. * * @param title the title of the note * @param body the body of the note * @return rowId or -1 if failed */ public long createNote(String title, String body) { ContentValues initialValues = new ContentValues(); initialValues.put(KEY_FROM, title); initialValues.put(KEY_TO, body); return mDb.insert(DATABASE_NOTESTABLE, null, initialValues); } /** * Create a new route using the title and body provided. If the route is * successfully created return the new rowId for that route, otherwise return * a -1 to indicate failure. * * @param start the start time of the route * @param arrival the arrival time of the route * @param line the line number of the route * @param duration the routes duration * @return rowId or -1 if failed */ public long createRoute(String start, String arrival, String line, String duration){ ContentValues initialValues = new ContentValues(); initialValues.put(KEY_START, start); initialValues.put(KEY_ARRIVAL, arrival); initialValues.put(KEY_LINE, line); initialValues.put(KEY_DURATION, duration); return mDb.insert(DATABASE_ROUTESTABLE, null, initialValues); } /** * Delete the note with the given rowId * * @param rowId id of note to delete * @return true if deleted, false otherwise */ public boolean deleteNote(long rowId) { return mDb.delete(DATABASE_NOTESTABLE, KEY_ROWID + "=" + rowId, null) > 0; } /** * Return a Cursor over the list of all notes in the database * * @return Cursor over all notes */ public Cursor fetchAllNotes() { return mDb.query(DATABASE_NOTESTABLE, new String[] {KEY_ROWID, KEY_FROM, KEY_TO}, null, null, null, null, null); } /** * Return a Cursor over the list of all routes in the database * * @return Cursor over all routes */ public Cursor fetchAllRoutes() { return mDb.query(DATABASE_ROUTESTABLE, new String[] {KEY_ROWID, KEY_START, KEY_ARRIVAL, KEY_LINE, KEY_DURATION}, null, null, null, null, null); } /** * Return a Cursor positioned at the note that matches the given rowId * * @param rowId id of note to retrieve * @return Cursor positioned to matching note, if found * @throws SQLException if note could not be found/retrieved */ public Cursor fetchNote(long rowId) throws SQLException { Cursor mCursor = mDb.query(true, DATABASE_NOTESTABLE, new String[] {KEY_ROWID, KEY_FROM, KEY_TO}, KEY_ROWID + "=" + rowId, null, null, null, null, null); if (mCursor != null) { mCursor.moveToFirst(); } return mCursor; } /** * Return a Cursor positioned at the route that matches the given rowId * * @param rowId id of route to retrieve * @return Cursor positioned to matching route * @throws SQLException if note could not be found/retrieved */ public Cursor fetchRoute(long rowId) throws SQLException { Cursor mCursor = mDb.query(true, DATABASE_ROUTESTABLE, new String[] {KEY_ROWID, KEY_START, KEY_ARRIVAL, KEY_LINE, KEY_DURATION}, KEY_ROWID + "=" + rowId, null, null, null, null, null); if (mCursor != null) { mCursor.moveToFirst(); } return mCursor; } /** * Update the note using the details provided. The note to be updated is * specified using the rowId, and it is altered to use the title and body * values passed in * * @param rowId id of note to update * @param title value to set note title to * @param body value to set note body to * @return true if the note was successfully updated, false otherwise */ public boolean updateNote(long rowId, String title, String body) { ContentValues args = new ContentValues(); args.put(KEY_FROM, title); args.put(KEY_TO, body); return mDb.update(DATABASE_NOTESTABLE, args, KEY_ROWID + "=" + rowId, null) > 0; } }

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• How can I enable PHP5 for a site? Having problems with every single method.

  - by John Stephens

  I'm working on a client site that is hosted on someone's DIY Debian Linux server [Apache/1.3.33 (Debian GNU/Linux)], and I'm trying to install a script that requires PHP5. By default, the server parses .php files with PHP 4.3.10-22, which is configured at /etc/php4/apache/php.ini, according to phpinfo(). On the server I can see a config directory for PHP5 adjacent to the PHP4 directory: /etc/php5.0/apache2/php.ini. I have tried multiple methods to enable PHP5 for the document root where the site's files are hosted, including all available methods mentioned here. By far, the most common suggestion I've found is to add one or both of the following lines to the site's .htaccess file: AddHandler application/x-httpd-php5 .php AddType application/x-httpd-php5 .php Trouble is, when either or both of those lines are present, the site forces my browser to download any .php files requested, without parsing the PHP at all. All of the other methods mentioned in the above article cause a 500 Internal Server Error. There is no hosting control panel I can access in a browser to enable PHP5 for the site, but I do have shell access. When I asked the server administrator about this issue, he encouraged me to search for the answer on Google. Where could I begin to troubleshoot this issue? Are there ways to test or verify the server's specific PHP5 installation and configuration, using the command line or some other method? Do you have other suggestions to enable PHP5?

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• Multiple routers, subnets, gateways etc

  - by allentown

  My current setup is: Cable modem dishes out 13 static IP's (/28), a GB switch is plugged into the cable modem, and has access to those 13 static IP's, I have about 6 "servers" in use right now. The cable modem is also a firewall, DHCP server, and 3 port 10/100 switch. I am using it as a firewall, but not currently as a DHCP server. I have plugged into the cable modem, two network cables, one which goes to the WAN port of a Linksys Dual Band Wireless 10/100/1000 router/switch. Into the linksys are a few workstations, a few printers, and some laptops connecting to wifi. I set the Linksys to use take static IP, and enabled DHCP for the workstations, printers, etc in 192.168.1.1/24. The network for the Linksys is mostly self contained, backups go to a SAN, on that network, it all happens through that switch, over GB. But I also get internet access from it as well via the cable modem using one static IP. This all works, however, I can not "see" the static IP machines when I am on the Linksys. I can get to them via ssh and other protocols, and if I want to from "outside", I open holes, like 80, 25, 587, 143, 22, etc. The second wire, from the cable modem/fireall/switch just uplinks to the managed GB switch. What are the pros and cons of this? I do not like giving up the static IP to the Linksys. I basically have a mixed network of public servers, and internal workstations. I want the public servers on public IP's because I do not want to mess with port forwarding and mappings. Is it correct also, that if someone breaches the Linksys wifi, they still would have a hard time getting to the static IP range, just by nature of the network topology? Today, just for a test, I toggled on the DHCP in the firewall/cable modem at 10.1.10.1/24 range, the Linksys is n the 192.168.1.100/24 range. At that point, all the static IP machines still had in and out access, but Linksys was unreachable. The cable modem only has 10/100 ports, so I will not plug anything but the network drop into it, which is 50Mb/10Mb. Which makes me think this could be less than ideal, as transfers from the workstation network to the server network will be bottlenecked at 100Mb when I have 1000Mb available. I may not need to solve that, if isolation is better though. I do not move a lot of data, if any, from Linsys network to server network, so for it to pretend to be remote is ok. Should I approach this any different? I could enable DHCP on the cable modem/firewall, it should still send out the statics to the GB switch, but will also be a DHCP in 10.1.10.1/24 range? I can then plug the Linksys into the GB switch, which is now picking up statics and the 10.1.10.1/24 ranges, tell the Linksys to use 10.1.10.5 or so. Now, do I disable DHCP on the Linksys, and the cable modem/firewall will pass through the statics and 10.0.10.1/24 ranges as well? Or, could I open a second DHCP pool on the Linksys? I guess doing so gives me network isolation again, but it is just the reverse of what I have now. But I get out of the bottleneck, not that the Linksys could ever really touch real GB speeds anyway, but the managed switch certainly can. This is all because 13 statics are not that many. Right now, 6 "servers", the Linksys, a managed switch, a few SSL certs, and I am running out. I do not want to waste a static IP on the managed GB switch, or the Linksys, unless it provides me some type of benefit. Final question, under my current setup, if I am on a workstation, sitting at 192.168.1.109, the Linksys, with GB, and I send a file over ssh to the static IP machine, is that literally leaving the internet, and coming back in, or does it stay local? To me it seems like: Workstation (192.168.1.109) -> Linksys DHCP -> Linksys Static IP -> Cable Modem -> Server ( and it hits the 10/100 ports on the cable modem, slowing me down. But does it round trip the network, leave and come back in, limiting me to the 50/10 internet speeds? *These are all made up numbers, I do not use default router IP's as I will one day add a VPN, and do not want collisions. I need some recommendations, do I want one big network, or two isolated ones. Printers these days need an IP, everything does, I can not get autoconf/bonjour to be reliable on most printers. but I am also not sure I want the "server" side of my operation to be polluted by the workstation side of my operation. Unless there is some magic subetting I have not learned yet, here is what I am thinking: Cable modem 10/100, has 13 static IP, publicly accessible -> Enable DHCP on the cable modem -> Cable modem plugs into managed switch -> Managed switch gets 10.1.10.1 ssh, telnet, https admin management address -> Managed switch sends static IP's to to servers -> Plug Linksys into managed switch, giving it 10.1.10.2 static internally in Linksys admin -> Linksys gets assigned 10.1.10.x as its DHCP sending range -> Local printers, workstations, iPhones etc, connect to this -> ( Do I enable DHCP or disable it on the Linksys, just define a non over lapping range, or create an entirely new DHCP at 10.1.50.0/24, I think I am back isolated again with that method too? ) Thank you for any suggestions. This is the first time I have had to deal with less than a /24, and most are larger than that, but it is just a drop to a cabinet. Otherwise, it's a router, a few repeaters, and soho stuff that is simple, with one IP. I know a few may suggest going all DHCP on the servers, and I may one day, just not now, there has been too much moving of gear for me to be interested in that, and I would want something in the Catalyst series to deal with that.

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• Profiling Startup Of VS2012 &ndash; SpeedTrace Profiler

  - by Alois Kraus

  SpeedTrace is a relatively unknown profiler made a company called Ipcas. A single professional license does cost 449€+VAT. For the test I did use SpeedTrace 4.5 which is currently Beta. Although it is cheaper than dotTrace it has by far the most options to influence how profiling does work. First you need to create a tracing project which does configure tracing for one process type. You can start the application directly from the profiler or (much more interesting) it does attach to a specific process when it is started. For this you need to check “Trace the specified …” radio button and enter the process name in the “Process Name of the Trace” edit box. You can even selectively enable tracing for processes with a specific command line. Then you need to activate the trace project by pressing the Activate Project button and you are ready to start VS as usual. If you want to profile the next 10 VS instances that you start you can set the Number of Processes counter to e.g. 10. This is immensely helpful if you are trying to profile only the next 5 started processes. As you can see there are many more tabs which do allow to influence tracing in a much more sophisticated way. SpeedTrace is the only profiler which does not rely entirely on the profiling Api of .NET. Instead it does modify the IL code (instrumentation on the fly) to write tracing information to disc which can later be analyzed. This approach is not only very fast but it does give you unprecedented analysis capabilities. Once the traces are collected they do show up in your workspace where you can open the trace viewer. I do skip the other windows because this view is by far the most useful one. You can sort the methods not only by Wall Clock time but also by CPU consumption and wait time which none of the other products support in their views at the same time. If you want to optimize for CPU consumption sort by CPU time. If you want to find out where most time is spent you need Clock Total time and Clock Waiting. There you can directly see if the method did take long because it did wait on something or it did really execute stuff that did take so long. Once you have found a method you want to drill deeper you can double click on a method to get to the Caller/Callee view which is similar to the JetBrains Method Grid view. But this time you do see much more. In the middle is the clicked method. Above are the methods that call you and below are the methods that you do directly call. Normally you would then start digging deeper to find the end of the chain where the slow method worth optimizing is located. But there is a shortcut. You can press the magic   button to calculate the aggregation of all called methods. This is displayed in the lower left window where you can see each method call and how long it did take. There you can also sort to see if this call stack does only contain methods (e.g. WCF connect calls which you cannot make faster) not worth optimizing. YourKit has a similar feature where it is called Callees List. In the Functions tab you have in the context menu also many other useful analysis options One really outstanding feature is the View Call History Drilldown. When you select this one you get not a sum of all method invocations but a list with the duration of each method call. This is not surprising since SpeedTrace does use tracing to get its timings. There you can get many useful graphs how this method did behave over time. Did it become slower at some point in time or was only the first call slow? The diagrams and the list will tell you that. That is all fine but what should I do when one method call was slow? I want to see from where it was coming from. No problem select the method in the list hit F10 and you get the call stack. This is a life saver if you e.g. search for serialization problems. Today Serializers are used everywhere. You want to find out from where the 5s XmlSerializer.Deserialize call did come from? Hit F10 and you get the call stack which did invoke the 5s Deserialize call. The CPU timeline tab is also useful to find out where long pauses or excessive CPU consumption did happen. Click in the graph to get the Thread Stacks window where you can get a quick overview what all threads were doing at this time. This does look like the Stack Traces feature in YourKit. Only this time you get the last called method first which helps to quickly see what all threads were executing at this moment. YourKit does generate a rather long list which can be hard to go through when you have many threads. The thread list in the middle does not give you call stacks or anything like that but you see which methods were found most often executing code by the profiler which is a good indication for methods consuming most CPU time. This does sound too good to be true? I have not told you the best part yet. The best thing about this profiler is the staff behind it. When I do see a crash or some other odd behavior I send a mail to Ipcas and I do get usually the next day a mail that the problem has been fixed and a download link to the new version. The guys at Ipcas are even so helpful to log in to your machine via a Citrix Client to help you to get started profiling your actual application you want to profile. After a 2h telco I was converted from a hater to a believer of this tool. The fast response time might also have something to do with the fact that they are actively working on 4.5 to get out of the door. But still the support is by far the best I have encountered so far. The only downside is that you should instrument your assemblies including the .NET Framework to get most accurate numbers. You can profile without doing it but then you will see very high JIT times in your process which can severely affect the correctness of the measured timings. If you do not care about exact numbers you can also enable in the main UI in the Data Trace tab logging of method arguments of primitive types. If you need to know what files at which times were opened by your application you can find it out without a debugger. Since SpeedTrace does read huge trace files in its reader you should perhaps use a 64 bit machine to be able to analyze bigger traces as well. The memory consumption of the trace reader is too high for my taste. But they did promise for the next version to come up with something much improved.

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• Delegates in .NET: how are they constructed ?

  - by Saulius

  While inspecting delegates in C# and .NET in general, I noticed some interesting facts: Creating a delegate in C# creates a class derived from MulticastDelegate with a constructor: .method public hidebysig specialname rtspecialname instance void .ctor(object 'object', native int 'method') runtime managed { } Meaning that it expects the instance and a pointer to the method. Yet the syntax of constructing a delegate in C# suggests that it has a constructor new MyDelegate(int () target) where I can recognise int () as a function instance (int *target() would be a function pointer in C++). So obviously the C# compiler picks out the correct method from the method group defined by the function name and constructs the delegate. So the first question would be, where does the C# compiler (or Visual Studio, to be precise) pick this constructor signature from ? I did not notice any special attributes or something that would make a distinction. Is this some sort of compiler/visualstudio magic ? If not, is the T (args) target construction valid in C# ? I did not manage to get anything with it to compile, e.g.: int () target = MyMethod; is invalid, so is doing anything with MyMetod, e.g. calling .ToString() on it (well this does make some sense, since that is technically a method group, but I imagine it should be possible to explicitly pick out a method by casting, e.g. (int())MyFunction. So is all of this purely compiler magic ? Looking at the construction through reflector reveals yet another syntax: Func CS$1$0000 = new Func(null, (IntPtr) Foo); This is consistent with the disassembled constructor signature, yet this does not compile! One final interesting note is that the classes Delegate and MulticastDelegate have yet another sets of constructors: .method family hidebysig specialname rtspecialname instance void .ctor(class System.Type target, string 'method') cil managed Where does the transition from an instance and method pointer to a type and a string method name occur ? Can this be explained by the runtime managed keywords in the custom delegate constructor signature, i.e. does the runtime do it's job here ?

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• Singleton code linker errors in vc 9.0. Runs fine in linux compiled with gcc

  - by user306560

  I have a simple logger that is implemented as a singleton. It works like i want when I compile and run it with g++ in linux but when I compile in Visual Studio 9.0 with vc++ I get the following errors. Is there a way to fix this? I don't mind changing the logger class around, but I would like to avoid changing how it is called. 1>Linking... 1>loggerTest.obj : error LNK2005: "public: static class Logger * __cdecl Logger::getInstance(void)" (?getInstance@Logger@@SAPAV1@XZ) already defined in Logger.obj 1>loggerTest.obj : error LNK2005: "public: void __thiscall Logger::log(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > const &)" (?log@Logger@@QAEXABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@Z) already defined in Logger.obj 1>loggerTest.obj : error LNK2005: "public: void __thiscall Logger::closeLog(void)" (?closeLog@Logger@@QAEXXZ) already defined in Logger.obj 1>loggerTest.obj : error LNK2005: "private: static class Logger * Logger::_instance" (?_instance@Logger@@0PAV1@A) already defined in Logger.obj 1>Logger.obj : error LNK2001: unresolved external symbol "private: static class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > Logger::_path" (?_path@Logger@@0V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@A) 1>loggerTest.obj : error LNK2001: unresolved external symbol "private: static class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > Logger::_path" (?_path@Logger@@0V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@A) 1>Logger.obj : error LNK2001: unresolved external symbol "private: static class boost::mutex Logger::_mutex" (?_mutex@Logger@@0Vmutex@boost@@A) 1>loggerTest.obj : error LNK2001: unresolved external symbol "private: static class boost::mutex Logger::_mutex" (?_mutex@Logger@@0Vmutex@boost@@A) 1>Logger.obj : error LNK2001: unresolved external symbol "private: static class std::basic_ofstream<char,struct std::char_traits<char> > Logger::_log" (?_log@Logger@@0V?$basic_ofstream@DU?$char_traits@D@std@@@std@@A) 1>loggerTest.obj : error LNK2001: unresolved external symbol "private: static class std::basic_ofstream<char,struct std::char_traits<char> > Logger::_log" (?_log@Logger@@0V?$basic_ofstream@DU?$char_traits@D@std@@@std@@A) The code, three files Logger.h Logger.cpp test.cpp #ifndef __LOGGER_CPP__ #define __LOGGER_CPP__ #include "Logger.h" Logger* Logger::_instance = 0; //string Logger::_path = "log"; //ofstream Logger::_log; //boost::mutex Logger::_mutex; Logger* Logger::getInstance(){ { boost::mutex::scoped_lock lock(_mutex); if(_instance == 0) { _instance = new Logger; _path = "log"; } } //mutex return _instance; } void Logger::log(const std::string& msg){ { boost::mutex::scoped_lock lock(_mutex); if(!_log.is_open()){ _log.open(_path.c_str()); } if(_log.is_open()){ _log << msg.c_str() << std::endl; } } } void Logger::closeLog(){ Logger::_log.close(); } #endif ` ... #ifndef __LOGGER_H__ #define __LOGGER_H__ #include <iostream> #include <string> #include <fstream> #include <boost/thread/mutex.hpp> #include <boost/thread.hpp> using namespace std; class Logger { public: static Logger* getInstance(); void log(const std::string& msg); void closeLog(); protected: Logger(){} private: static Logger* _instance; static string _path; static bool _logOpen; static ofstream _log; static boost::mutex _mutex; //check mutable }; #endif test.cpp ` #include <iostream> #include "Logger.cpp" using namespace std; int main(int argc, char *argv[]) { Logger* log = Logger::getInstance(); log->log("hello world\n"); return 0; }

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• Grails: Querying Associations causes groovy.lang.MissingMethodException

  - by Paul

  Hi, I've got an issue with Grails where I have a test app with: class Artist { static constraints = { name() } static hasMany = [albums:Album] String name } class Album { static constraints = { name() } static hasMany = [ tracks : Track ] static belongsTo = [artist: Artist] String name } class Track { static constraints = { name() lyrics(nullable: true) } Lyrics lyrics static belongsTo = [album: Album] String name } The following query (and a more advanced, nested association query) works in the Grails Console but fails with a groovy.lang.MissingMethodException when running the app with 'run-app': def albumCriteria = tunehub.Album.createCriteria() def albumResults = albumCriteria.list { like("name", receivedAlbum) artist { like("name", receivedArtist) } // Fails here maxResults(1) } Stacktrace: groovy.lang.MissingMethodException: No signature of method: java.lang.String.call() is applicable for argument types: (tunehub.LyricsService$_getLyrics_closure1_closure2) values: [tunehub.LyricsService$_getLyrics_closure1_closure2@604106] Possible solutions: wait(), any(), wait(long), each(groovy.lang.Closure), any(groovy.lang.Closure), trim() at tunehub.LyricsService$_getLyrics_closure1.doCall(LyricsService.groovy:61) at tunehub.LyricsService$_getLyrics_closure1.doCall(LyricsService.groovy) (...truncated...) Any pointers?

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• Parsing Concerns

  - by Jesse

  If you’ve ever written an application that accepts date and/or time inputs from an external source (a person, an uploaded file, posted XML, etc.) then you’ve no doubt had to deal with parsing some text representing a date into a data structure that a computer can understand. Similarly, you’ve probably also had to take values from those same data structure and turn them back into their original formats. Most (all?) suitably modern development platforms expose some kind of parsing and formatting functionality for turning text into dates and vice versa. In .NET, the DateTime data structure exposes ‘Parse’ and ‘ToString’ methods for this purpose. This post will focus mostly on parsing, though most of the examples and suggestions below can also be applied to the ToString method. The DateTime.Parse method is pretty permissive in the values that it will accept (though apparently not as permissive as some other languages) which makes it pretty easy to take some text provided by a user and turn it into a proper DateTime instance. Here are some examples (note that the resulting DateTime values are shown using the RFC1123 format): DateTime.Parse("3/12/2010"); //Fri, 12 Mar 2010 00:00:00 GMT DateTime.Parse("2:00 AM"); //Sat, 01 Jan 2011 02:00:00 GMT (took today's date as date portion) DateTime.Parse("5-15/2010"); //Sat, 15 May 2010 00:00:00 GMT DateTime.Parse("7/8"); //Fri, 08 Jul 2011 00:00:00 GMT DateTime.Parse("Thursday, July 1, 2010"); //Thu, 01 Jul 2010 00:00:00 GMT Dealing With Inaccuracy While the DateTime struct has the ability to store a date and time value accurate down to the millisecond, most date strings provided by a user are not going to specify values with that much precision. In each of the above examples, the Parse method was provided a partial value from which to construct a proper DateTime. This means it had to go ahead and assume what you meant and fill in the missing parts of the date and time for you. This is a good thing, especially when we’re talking about taking input from a user. We can’t expect that every person using our software to provide a year, day, month, hour, minute, second, and millisecond every time they need to express a date. That said, it’s important for developers to understand what assumptions the software might be making and plan accordingly. I think the assumptions that were made in each of the above examples were pretty reasonable, though if we dig into this method a little bit deeper we’ll find that there are a lot more assumptions being made under the covers than you might have previously known. One of the biggest assumptions that the DateTime.Parse method has to make relates to the format of the date represented by the provided string. Let’s consider this example input string: ‘10-02-15’. To some people. that might look like ‘15-Feb-2010’. To others, it might be ‘02-Oct-2015’. Like many things, it depends on where you’re from. This Is America! Most cultures around the world have adopted a “little-endian” or “big-endian” formats. (Source: Date And Time Notation By Country) In this context,  a “little-endian” date format would list the date parts with the least significant first while the “big-endian” date format would list them with the most significant first. For example, a “little-endian” date would be “day-month-year” and “big-endian” would be “year-month-day”. It’s worth nothing here that ISO 8601 defines a “big-endian” format as the international standard. While I personally prefer “big-endian” style date formats, I think both styles make sense in that they follow some logical standard with respect to ordering the date parts by their significance. Here in the United States, however, we buck that trend by using what is, in comparison, a completely nonsensical format of “month/day/year”. Almost no other country in the world uses this format. I’ve been fortunate in my life to have done some international travel, so I’ve been aware of this difference for many years, but never really thought much about it. Until recently, I had been developing software for exclusively US-based audiences and remained blissfully ignorant of the different date formats employed by other countries around the world. The web application I work on is being rolled out to users in different countries, so I was recently tasked with updating it to support different date formats. As it turns out, .NET has a great mechanism for dealing with different date formats right out of the box. Supporting date formats for different cultures is actually pretty easy once you understand this mechanism. Pulling the Curtain Back On the Parse Method Have you ever taken a look at the different flavors (read: overloads) that the DateTime.Parse method comes in? In it’s simplest form, it takes a single string parameter and returns the corresponding DateTime value (if it can divine what the date value should be). You can optionally provide two additional parameters to this method: an ‘System.IFormatProvider’ and a ‘System.Globalization.DateTimeStyles’. Both of these optional parameters have some bearing on the assumptions that get made while parsing a date, but for the purposes of this article I’m going to focus on the ‘System.IFormatProvider’ parameter. The IFormatProvider exposes a single method called ‘GetFormat’ that returns an object to be used for determining the proper format for displaying and parsing things like numbers and dates. This interface plays a big role in the globalization capabilities that are built into the .NET Framework. The cornerstone of these globalization capabilities can be found in the ‘System.Globalization.CultureInfo’ class. To put it simply, the CultureInfo class is used to encapsulate information related to things like language, writing system, and date formats for a certain culture. Support for many cultures are “baked in” to the .NET Framework and there is capacity for defining custom cultures if needed (thought I’ve never delved into that). While the details of the CultureInfo class are beyond the scope of this post, so for now let me just point out that the CultureInfo class implements the IFormatInfo interface. This means that a CultureInfo instance created for a given culture can be provided to the DateTime.Parse method in order to tell it what date formats it should expect. So what happens when you don’t provide this value? Let’s crack this method open in Reflector: When no IFormatInfo parameter is provided (i.e. we use the simple DateTime.Parse(string) overload), the ‘DateTimeFormatInfo.CurrentInfo’ is used instead. Drilling down a bit further we can see the implementation of the DateTimeFormatInfo.CurrentInfo property: From this property we can determine that, in the absence of an IFormatProvider being specified, the DateTime.Parse method will assume that the provided date should be treated as if it were in the format defined by the CultureInfo object that is attached to the current thread. The culture specified by the CultureInfo instance on the current thread can vary depending on several factors, but if you’re writing an application where a single instance might be used by people from different cultures (i.e. a web application with an international user base), it’s important to know what this value is. Having a solid strategy for setting the current thread’s culture for each incoming request in an internationally used ASP .NET application is obviously important, and might make a good topic for a future post. For now, let’s think about what the implications of not having the correct culture set on the current thread. Let’s say you’re running an ASP .NET application on a server in the United States. The server was setup by English speakers in the United States, so it’s configured for US English. It exposes a web page where users can enter order data, one piece of which is an anticipated order delivery date. Most users are in the US, and therefore enter dates in a ‘month/day/year’ format. The application is using the DateTime.Parse(string) method to turn the values provided by the user into actual DateTime instances that can be stored in the database. This all works fine, because your users and your server both think of dates in the same way. Now you need to support some users in South America, where a ‘day/month/year’ format is used. The best case scenario at this point is a user will enter March 13, 2011 as ‘25/03/2011’. This would cause the call to DateTime.Parse to blow up since that value doesn’t look like a valid date in the US English culture (Note: In all likelihood you might be using the DateTime.TryParse(string) method here instead, but that method behaves the same way with regard to date formats). “But wait a minute”, you might be saying to yourself, “I thought you said that this was the best case scenario?” This scenario would prevent users from entering orders in the system, which is bad, but it could be worse! What if the order needs to be delivered a day earlier than that, on March 12, 2011? Now the user enters ‘12/03/2011’. Now the call to DateTime.Parse sees what it thinks is a valid date, but there’s just one problem: it’s not the right date. Now this order won’t get delivered until December 3, 2011. In my opinion, that kind of data corruption is a much bigger problem than having the Parse call fail. What To Do? My order entry example is a bit contrived, but I think it serves to illustrate the potential issues with accepting date input from users. There are some approaches you can take to make this easier on you and your users: Eliminate ambiguity by using a graphical date input control. I’m personally a fan of a jQuery UI Datepicker widget. It’s pretty easy to setup, can be themed to match the look and feel of your site, and has support for multiple languages and cultures. Be sure you have a way to track the culture preference of each user in your system. For a web application this could be done using something like a cookie or session state variable. Ensure that the current user’s culture is being applied correctly to DateTime formatting and parsing code. This can be accomplished by ensuring that each request has the handling thread’s CultureInfo set properly, or by using the Format and Parse method overloads that accept an IFormatProvider instance where the provided value is a CultureInfo object constructed using the current user’s culture preference. When in doubt, favor formats that are internationally recognizable. Using the string ‘2010-03-05’ is likely to be recognized as March, 5 2011 by users from most (if not all) cultures. Favor standard date format strings over custom ones. So far we’ve only talked about turning a string into a DateTime, but most of the same “gotchas” apply when doing the opposite. Consider this code: someDateValue.ToString("MM/dd/yyyy"); This will output the same string regardless of what the current thread’s culture is set to (with the exception of some cultures that don’t use the Gregorian calendar system, but that’s another issue all together). For displaying dates to users, it would be better to do this: someDateValue.ToString("d"); This standard format string of “d” will use the “short date format” as defined by the culture attached to the current thread (or provided in the IFormatProvider instance in the proper method overload). This means that it will honor the proper month/day/year, year/month/day, or day/month/year format for the culture. Knowing Your Audience The examples and suggestions shown above can go a long way toward getting an application in shape for dealing with date inputs from users in multiple cultures. There are some instances, however, where taking approaches like these would not be appropriate. In some cases, the provider or consumer of date values that pass through your application are not people, but other applications (or other portions of your own application). For example, if your site has a page that accepts a date as a query string parameter, you’ll probably want to format that date using invariant date format. Otherwise, the same URL could end up evaluating to a different page depending on the user that is viewing it. In addition, if your application exports data for consumption by other systems, it’s best to have an agreed upon format that all systems can use and that will not vary depending upon whether or not the users of the systems on either side prefer a month/day/year or day/month/year format. I’ll look more at some approaches for dealing with these situations in a future post. If you take away one thing from this post, make it an understanding of the importance of knowing where the dates that pass through your system come from and are going to. You will likely want to vary your parsing and formatting approach depending on your audience.

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• Sql Server as logging, best connection practise

  - by ozz

  I'm using SqlServer as logging. Yes this is wrong decision, there are better dbs for this requirement. But I have no other option for now. Logging interval is 3 logs per second. So I've static Logger class and it has static Log method. Using "Open Connection" as static member is better for performance. But what is the best implemantation of it? This is not that I know. public static class OzzLogger { static SqlConnection Con; static OzzLogger() { Con=ne SqlConnection(....); Con.Open(); } public static void Log(....) { Con.ExecuteSql(......); } } UPDATE I asked because of my old information. People say "connection pooling performance is enough". If there is no objection I'm closing the issue :)

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• How do I replace "this" in Java with something that works.

  - by Luke Alderton

  I'm looking to get the showGUI() method work, the compiler says "this" is not a static variable and cannot be referenced from a static context, what would I use to replace "this"? I've tried test.main (test being the package it's in). The reason I'm using the static method showGUI() is because I need the method to be called from another static method, as well as the startup() method. Below are my two main classes. public class Main extends SingleFrameApplication { @Override protected void startup() { showGUI(); } @Override protected void configureWindow(java.awt.Window root) { } public static Main getApplication() { return Application.getInstance(Main.class); } public static void main(String[] args) { launch(Main.class, args); } public static void showGUI() { show(new GUI(this)); } } public class GUI extends FrameView { public GUI(SingleFrameApplication app) { super(app); initComponents(); } private void initComponents() { //all the GUI stuff is somehow defined here } }

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• NLog Exception Details Renderer

  - by jtimperley

  Originally posted on: http://geekswithblogs.net/jtimperley/archive/2013/07/28/nlog-exception-details-renderer.aspxI recently switch from Microsoft's Enterprise Library Logging block to NLog.  In my opinion, NLog offers a simpler and much cleaner configuration section with better use of placeholders, complemented by custom variables. Despite this, I found one deficiency in my migration; I had lost the ability to simply render all details of an exception into our logs and notification emails. This is easily remedied by implementing a custom layout renderer. Start by extending 'NLog.LayoutRenderers.LayoutRenderer' and overriding the 'Append' method. using System.Text; using NLog; using NLog.Config; using NLog.LayoutRenderers;   [ThreadAgnostic] [LayoutRenderer(Name)] public class ExceptionDetailsRenderer : LayoutRenderer { public const string Name = "exceptiondetails";   protected override void Append(StringBuilder builder, LogEventInfo logEvent) { // Todo: Append details to StringBuilder } }   Now that we have a base layout renderer, we simply need to add the formatting logic to add exception details as well as inner exception details. This is done using reflection with some simple filtering for the properties that are already being rendered. I have added an additional 'Register' method, allowing the definition to be registered in code, rather than in configuration files. This complements by 'LogWrapper' class which standardizes writing log entries throughout my applications. using System; using System.Collections.Generic; using System.Linq; using System.Reflection; using System.Text; using NLog; using NLog.Config; using NLog.LayoutRenderers;   [ThreadAgnostic] [LayoutRenderer(Name)] public sealed class ExceptionDetailsRenderer : LayoutRenderer { public const string Name = "exceptiondetails"; private const string _Spacer = "======================================"; private List<string> _FilteredProperties;   private List<string> FilteredProperties { get { if (_FilteredProperties == null) { _FilteredProperties = new List<string> { "StackTrace", "HResult", "InnerException", "Data" }; }   return _FilteredProperties; } }   public bool LogNulls { get; set; }   protected override void Append(StringBuilder builder, LogEventInfo logEvent) { Append(builder, logEvent.Exception, false); }   private void Append(StringBuilder builder, Exception exception, bool isInnerException) { if (exception == null) { return; }   builder.AppendLine();   var type = exception.GetType(); if (isInnerException) { builder.Append("Inner "); }   builder.AppendLine("Exception Details:") .AppendLine(_Spacer) .Append("Exception Type: ") .AppendLine(type.ToString());   var bindingFlags = BindingFlags.Instance | BindingFlags.Public; var properties = type.GetProperties(bindingFlags); foreach (var property in properties) { var propertyName = property.Name; var isFiltered = FilteredProperties.Any(filter => String.Equals(propertyName, filter, StringComparison.InvariantCultureIgnoreCase)); if (isFiltered) { continue; }   var propertyValue = property.GetValue(exception, bindingFlags, null, null, null); if (propertyValue == null && !LogNulls) { continue; }   var valueText = propertyValue != null ? propertyValue.ToString() : "NULL"; builder.Append(propertyName) .Append(": ") .AppendLine(valueText); }   AppendStackTrace(builder, exception.StackTrace, isInnerException); Append(builder, exception.InnerException, true); }   private void AppendStackTrace(StringBuilder builder, string stackTrace, bool isInnerException) { if (String.IsNullOrEmpty(stackTrace)) { return; }   builder.AppendLine();   if (isInnerException) { builder.Append("Inner "); }   builder.AppendLine("Exception StackTrace:") .AppendLine(_Spacer) .AppendLine(stackTrace); }   public static void Register() { Type definitionType; var layoutRenderers = ConfigurationItemFactory.Default.LayoutRenderers; if (layoutRenderers.TryGetDefinition(Name, out definitionType)) { return; }   layoutRenderers.RegisterDefinition(Name, typeof(ExceptionDetailsRenderer)); LogManager.ReconfigExistingLoggers(); } } For brevity I have removed the Trace, Debug, Warn, and Fatal methods. They are modelled after the Info methods. As mentioned above, note how the log wrapper automatically registers our custom layout renderer reducing the amount of application configuration required. using System; using NLog;   public static class LogWrapper { static LogWrapper() { ExceptionDetailsRenderer.Register(); }   #region Log Methods   public static void Info(object toLog) { Log(toLog, LogLevel.Info); }   public static void Info(string messageFormat, params object[] parameters) { Log(messageFormat, parameters, LogLevel.Info); }   public static void Error(object toLog) { Log(toLog, LogLevel.Error); }   public static void Error(string message, Exception exception) { Log(message, exception, LogLevel.Error); }   private static void Log(string messageFormat, object[] parameters, LogLevel logLevel) { string message = parameters.Length == 0 ? messageFormat : string.Format(messageFormat, parameters); Log(message, (Exception)null, logLevel); }   private static void Log(object toLog, LogLevel logLevel, LogType logType = LogType.General) { if (toLog == null) { throw new ArgumentNullException("toLog"); }   if (toLog is Exception) { var exception = toLog as Exception; Log(exception.Message, exception, logLevel, logType); } else { var message = toLog.ToString(); Log(message, null, logLevel, logType); } }   private static void Log(string message, Exception exception, LogLevel logLevel, LogType logType = LogType.General) { if (exception == null && String.IsNullOrEmpty(message)) { return; }   var logger = GetLogger(logType); // Note: Using the default constructor doesn't set the current date/time var logInfo = new LogEventInfo(logLevel, logger.Name, message); logInfo.Exception = exception; logger.Log(logInfo); }   private static Logger GetLogger(LogType logType) { var loggerName = logType.ToString(); return LogManager.GetLogger(loggerName); }   #endregion   #region LogType private enum LogType { General } #endregion } The following configuration is similar to what is provided for each of my applications. The 'application' variable is all that differentiates the various applications in all of my environments, the rest has been standardized. Depending on your needs to tweak this configuration while developing and debugging, this section could easily be pushed back into code similar to the registering of our custom layout renderer.   <?xml version="1.0"?>   <configuration> <configSections> <section name="nlog" type="NLog.Config.ConfigSectionHandler, NLog"/> </configSections> <nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <variable name="application" value="Example"/> <targets> <target type="EventLog" name="EventLog" source="${application}" log="${application}" layout="${message}${onexception: ${newline}${exceptiondetails}}"/> <target type="Mail" name="Email" smtpServer="smtp.example.local" from="[email protected]" to="[email protected]" subject="(${machinename}) ${application}: ${level}" body="Machine: ${machinename}${newline}Timestamp: ${longdate}${newline}Level: ${level}${newline}Message: ${message}${onexception: ${newline}${exceptiondetails}}"/> </targets> <rules> <logger name="*" minlevel="Debug" writeTo="EventLog" /> <logger name="*" minlevel="Error" writeTo="Email" /> </rules> </nlog> </configuration>   Now go forward, create your custom exceptions without concern for including their custom properties in your exception logs and notifications.

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• C# Extension Methods - To Extend or Not To Extend...

  - by James Michael Hare

  I've been thinking a lot about extension methods lately, and I must admit I both love them and hate them. They are a lot like sugar, they taste so nice and sweet, but they'll rot your teeth if you eat them too much.   I can't deny that they aren't useful and very handy. One of the major components of the Shared Component library where I work is a set of useful extension methods. But, I also can't deny that they tend to be overused and abused to willy-nilly extend every living type.   So what constitutes a good extension method? Obviously, you can write an extension method for nearly anything whether it is a good idea or not. Many times, in fact, an idea seems like a good extension method but in retrospect really doesn't fit.   So what's the litmus test? To me, an extension method should be like in the movies when a person runs into their twin, separated at birth. You just know you're related. Obviously, that's hard to quantify, so let's try to put a few rules-of-thumb around them.   A good extension method should:     Apply to any possible instance of the type it extends.     Simplify logic and improve readability/maintainability.     Apply to the most specific type or interface applicable.     Be isolated in a namespace so that it does not pollute IntelliSense.     So let's look at a few examples in relation to these rules.   The first rule, to me, is the most important of all. Once again, it bears repeating, a good extension method should apply to all possible instances of the type it extends. It should feel like the long lost relative that should have been included in the original class but somehow was missing from the family tree.    Take this nifty little int extension, I saw this once in a blog and at first I really thought it was pretty cool, but then I started noticing a code smell I couldn't quite put my finger on. So let's look:       public static class IntExtensinos     {         public static int Seconds(int num)         {             return num * 1000;         }           public static int Minutes(int num)         {             return num * 60000;         }     }     This is so you could do things like:       ...     Thread.Sleep(5.Seconds());     ...     proxy.Timeout = 1.Minutes();     ...     Awww, you say, that's cute! Well, that's the problem, it's kitschy and it doesn't always apply (and incidentally you could achieve the same thing with TimeStamp.FromSeconds(5)). It's syntactical candy that looks cool, but tends to rot and pollute the code. It would allow things like:       total += numberOfTodaysOrders.Seconds();     which makes no sense and should never be allowed. The problem is you're applying an extension method to a logical domain, not a type domain. That is, the extension method Seconds() doesn't really apply to ALL ints, it applies to ints that are representative of time that you want to convert to milliseconds.    Do you see what I mean? The two problems, in a nutshell, are that a) Seconds() called off a non-time value makes no sense and b) calling Seconds() off something to pass to something that does not take milliseconds will be off by a factor of 1000 or worse.   Thus, in my mind, you should only ever have an extension method that applies to the whole domain of that type.   For example, this is one of my personal favorites:       public static bool IsBetween<T>(this T value, T low, T high)         where T : IComparable<T>     {         return value.CompareTo(low) >= 0 && value.CompareTo(high) <= 0;     }   This allows you to check if any IComparable<T> is within an upper and lower bound. Think of how many times you type something like:       if (response.Employee.Address.YearsAt >= 2         && response.Employee.Address.YearsAt <= 10)     {     ...     }     Now, you can instead type:       if(response.Employee.Address.YearsAt.IsBetween(2, 10))     {     ...     }     Note that this applies to all IComparable<T> -- that's ints, chars, strings, DateTime, etc -- and does not depend on any logical domain. In addition, it satisfies the second point and actually makes the code more readable and maintainable.   Let's look at the third point. In it we said that an extension method should fit the most specific interface or type possible. Now, I'm not saying if you have something that applies to enumerables, you create an extension for List, Array, Dictionary, etc (though you may have reasons for doing so), but that you should beware of making things TOO general.   For example, let's say we had an extension method like this:       public static T ConvertTo<T>(this object value)     {         return (T)Convert.ChangeType(value, typeof(T));     }         This lets you do more fluent conversions like:       double d = "5.0".ConvertTo<double>();     However, if you dig into Reflector (LOVE that tool) you will see that if the type you are calling on does not implement IConvertible, what you convert to MUST be the exact type or it will throw an InvalidCastException. Now this may or may not be what you want in this situation, and I leave that up to you. Things like this would fail:       object value = new Employee();     ...     // class cast exception because typeof(IEmployee) != typeof(Employee)     IEmployee emp = value.ConvertTo<IEmployee>();       Yes, that's a downfall of working with Convertible in general, but if you wanted your fluent interface to be more type-safe so that ConvertTo were only callable on IConvertibles (and let casting be a manual task), you could easily make it:         public static T ConvertTo<T>(this IConvertible value)     {         return (T)Convert.ChangeType(value, typeof(T));     }         This is what I mean by choosing the best type to extend. Consider that if we used the previous (object) version, every time we typed a dot ('.') on an instance we'd pull up ConvertTo() whether it was applicable or not. By filtering our extension method down to only valid types (those that implement IConvertible) we greatly reduce our IntelliSense pollution and apply a good level of compile-time correctness.   Now my fourth rule is just my general rule-of-thumb. Obviously, you can make extension methods as in-your-face as you want. I included all mine in my work libraries in its own sub-namespace, something akin to:       namespace Shared.Core.Extensions { ... }     This is in a library called Shared.Core, so just referencing the Core library doesn't pollute your IntelliSense, you have to actually do a using on Shared.Core.Extensions to bring the methods in. This is very similar to the way Microsoft puts its extension methods in System.Linq. This way, if you want 'em, you use the appropriate namespace. If you don't want 'em, they won't pollute your namespace.   To really make this work, however, that namespace should only include extension methods and subordinate types those extensions themselves may use. If you plant other useful classes in those namespaces, once a user includes it, they get all the extensions too.   Also, just as a personal preference, extension methods that aren't simply syntactical shortcuts, I like to put in a static utility class and then have extension methods for syntactical candy. For instance, I think it imaginable that any object could be converted to XML:       namespace Shared.Core     {         // A collection of XML Utility classes         public static class XmlUtility         {             ...             // Serialize an object into an xml string             public static string ToXml(object input)             {                 var xs = new XmlSerializer(input.GetType());                   // use new UTF8Encoding here, not Encoding.UTF8. The later includes                 // the BOM which screws up subsequent reads, the former does not.                 using (var memoryStream = new MemoryStream())                 using (var xmlTextWriter = new XmlTextWriter(memoryStream, new UTF8Encoding()))                 {                     xs.Serialize(xmlTextWriter, input);                     return Encoding.UTF8.GetString(memoryStream.ToArray());                 }             }             ...         }     }   I also wanted to be able to call this from an object like:       value.ToXml();     But here's the problem, if i made this an extension method from the start with that one little keyword "this", it would pop into IntelliSense for all objects which could be very polluting. Instead, I put the logic into a utility class so that users have the choice of whether or not they want to use it as just a class and not pollute IntelliSense, then in my extensions namespace, I add the syntactical candy:       namespace Shared.Core.Extensions     {         public static class XmlExtensions         {             public static string ToXml(this object value)             {                 return XmlUtility.ToXml(value);             }         }     }   So now it's the best of both worlds. On one hand, they can use the utility class if they don't want to pollute IntelliSense, and on the other hand they can include the Extensions namespace and use as an extension if they want. The neat thing is it also adheres to the Single Responsibility Principle. The XmlUtility is responsible for converting objects to XML, and the XmlExtensions is responsible for extending object's interface for ToXml().

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• How can I get my VB.NET forms application startup method to be Sub Main() in Program.vb?

  - by SLC

  Trying to get it to behave like C#, where there is a Program class with a static Main method. However, in the project properties, I cannot set Program.vb to be the startup object, only the forms (it is a forms application). Am I missing something? I am using the VS2010 and the latest VB.

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• Can I Create A Generic Method of a Type of Interface?

  - by DaveDev

  Is it possible to create a generic method with a signature like public static string MyMethod<IMyTypeOfInterface>(object dataToPassToInterface) { // an instance of IMyTypeOfInterface knows how to handle // the data that is passed in } Would I have to instantiate the Interface with (T)Activator.CreateInstance();?

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