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  • How are value types implemented in .NET

    - by Michael
    Been looking around the net and can't find any articles about how value types are actually implemented. For instance, an Int32 is a struct and it's direct parent is System.ValueType and that's ultimate parent is System.Object. Object is a class - I imagine ValueType is a class? What's the class hierarchy? What part does the CLR have to play? At what stage and how does the CLR know to allocate value types to the stack? (FYI, I am aware that value types are stored where they are declared).

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  • Data persistance with BufferedReader and PrintWriter?

    - by Nazgulled
    I have this simple application with a couple of classes which are all related. There's one, the main one, for which there is only one instance of. I need to save save and load that using a text stream. My instructor requirement is BufferedReader to load the stream and PrintWriter to save it. But is this even possible? To persist a data object/class with a text stream? I know how to do it with and object, using serialization. But I don't see how am I supposed to do it using text streams. Suggestions?

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  • Using locks inside a loop

    - by Xaqron
    // Member Variable private readonly object _syncLock = new object(); // Now inside a static method foreach (var lazyObject in plugins) { if ((string)lazyObject.Metadata["key"] = "something") { lock (_syncLock) { if (!lazyObject.IsValueCreated) lazyObject.value.DoSomething(); } return lazyObject.value; } } Here I need synchronized access per loop. There are many threads iterating this loop and based on the key they are looking for, a lazy instance is created and returned. lazyObject should not be created more that one time. Although Lazy class is for doing so and despite of the used lock, under high threading I have more than one instance created (I track this with a Interlocked.Increment on a volatile shared int and log it somewhere). The problem is I don't have access to definition of Lazy and MEF defines how the Lazy class create objects. My questions: 1) Why the lock doesn't work ? 2) Should I use an array of locks instead of one lock for performance improvement ?

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  • Converting Byte[] to String - Interbase to C# - InvalidCastException

    - by NorthernOutpost
    I'm using OleDbDataReader rdr to read a "Comments" field in BLOB form (sub_type 1 segment size 80) into a string from an Interbase DB, and I keep getting exceptions. Any suggestions? Attempt #1 ls_Chap_Comments.Add((rdr["Comments"]).ToString()); InvalidCastException: The data value could not be converted for reasons other than sign mismatch or data overflow. For example, the data was corrupted in the data store but the row was still retrievable." Attempt #2 byte[] b = new byte[100]; b = (byte[])rdr["Comments"]; string s = System.Text.ASCIIEncoding.ASCII.GetString(b); InvalidCastException: Unable to cast object of type System.String to type System.Byte[] Attempt #3 // 17 is the BLOB column zero-based location for "Comments" retval = rdr.GetBytes(17, startIndex, outbyte, 0, bufferSize); InvalidCastException: Unable to cast object of type System.String to type System.Byte[]. Any suggestions would be really appreciated!

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  • How do I check for Existence of a Record in GAE

    - by VDev
    I am trying to create a simple view in Django & GAE, which will check if the user has a profile entity and prints a different message for each case. I have the program below, but somehow GAE always seem to return a object. My program is below import datetime from django.http import HttpResponse, HttpResponseRedirect from google.appengine.api import users from google.appengine.ext import db from models import Profile import logging #from accounts.views import profile # Create your views here. def login_view(request): user = users.get_current_user() profile = db.GqlQuery("SELECT * FROM Profile WHERE account = :1", users.get_current_user()) logging.info(profile) logging.info(user) if profile: return HttpResponse("Congratulations Your profile is already created.") else: return HttpResponse("Sorry Your profile is NOT created.") My model object is Profile defined as follows: class Profile(db.Model): first_name = db.StringProperty() last_name = db.StringProperty() gender = db.StringProperty(choices=set(["Male", "Female"])) account = db.UserProperty(required = True) friends = db.ListProperty(item_type=users.User) last_login = db.DateTimeProperty(required=True) Thanks for the help.

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  • Multi-threading concept and lock in c#

    - by Neeraj
    I read about lock, though not understood nothing at all. My question is why do we use a un-used object and lock that and how this makes something thread-safe or how this helps in multi-threading ? Isn't there other way to make thread-safe code. public class test { private object Lock { get; set; } ... lock (this.Lock) { ... } ... } Sorry is my question is very stupid, but i don't understand, although i've used it many times.

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  • C# Event routing in code behind

    - by Nate
    I'm building a WPF MVVM-ish application. I want to be able to display an event log containing items in a collection that exists in my viewmodel. I want any of the objects in the model to be able to add data to the event log. Therefore every object needs to be able to pass data back to one central collection for databinding in the view. I could implement an event in every one of my data classes and manually pass the events up the object heirarchy but this seems super clumsy. On the visual tree a Routed Event would take care of this, is there some equivelent in the model scope? Any other ideas?

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  • Pass parameter from page to ActiveX

    - by nCdy
    <object id="Bacs_DBTableRepX" classid="CLSID:CA8B72B3-3B15-40D7-9364-478E25AF5B41" codebase="Bacs_DBTableRepX.cab" style=" Z-INDEX: 102; LEFT: 20px; WIDTH: 1200px; POSITION: absolute; TOP: 80px; HEIGHT: 600px"> <param name="ax_Command" value='<%=GetText()%>'/> </object> Here is my try but it made no sense. Parameter had not being sent. Is there any examples how to sent parameter to my ActiveX or some mistakes in my code ?

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  • Exception wrapping and HTML pages

    - by dotnetdev
    Hi, We have a sharepoint 2007 project at work. The exception handling policy is to log to the Sharepoint logs. In this case, would the best approach be to call that method and then rethrow the exception higher up? Except if I rethrow it to be caught higher up, there is no other exception handling code so what would happen in this case? Also, if you are going to display a more friendly error to the user (which uses information in the exception object), then this would be a good use of exception wrapping. Would it be a good idea to make a custom aspx page and add these to customerrors, so that on init (not sure of the exact event), I can display exception info in the passed parameter on the page. However, a static html page can't do this so I don't see the point in wrapping exceptions (unless there is a page or alert which uses the exception object). So if a project uses html pages for errors, is there a point in wrapping exceptions? Thanks

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  • is there a way to add a variable/property to a DOM element (eg, an element returned by a jQuery sele

    - by bt
    Hi there, I am looking for an alternative to using an object/variable in global scope -- I would like to associate key/value pairs with specific DOM elements (eg, a DIV), so that I can use them as input for logic that processes other elements (eg, child elements of said DIV). I tried something naive like: $('[foo=bar]').key='value' , and $('[foo=bar]')[key]='value', but it puked. Doing something like: var foobar = $('[foo=bar]'); foobar.key = 'value' -- works, but the new property/value only affects the new object (ie, foobar, not $('[foo=bar]')) Most likely there's something terribly basic I am overlooking. Any help is appreciated, thanks!

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  • VB6 debugging- doesn't go to error handling code.

    - by Can Ho
    Hi, I'm maintaining a vb6 project(ActiveX DLL). When debugging, the app run into the following function: Public Function HasValue(ByVal vValue) As Boolean On Error GoTo Err If IsMissing(vValue) Then HasValue = False ElseIf IsNull(vValue) Or Len(vValue) = 0 Then HasValue = False ElseIf isEmpty(vValue) Then HasValue = False Else HasValue = True End If Exit Function Err: If IsArray(vValue) Or IsObject(vValue) Then HasValue = True Else HasValue = False End If End Function and it stops at the line ElseIf IsNull(vValue) Or Len(vValue) = 0 Then vValue is a custom object, contains some properties(obviously, not null). Although I didn't put any break point there, the app stopped there and alerted error dialog saying that "Run-time error '438': Object doesn't support this property or method". We had error handling code but the app didn't run to error handling code. It just stopped at the line causing the error and I had to stop the application. Do you have any idea about that? Thank you very much.

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  • C# 'could not found' existing method

    - by shybovycha
    Greetings! I've been fooling around (a bit) with C# and its assemblies. And so i've found such an interesting feature as dynamic loading assemblies and invoking its class members. A bit of google and here i am, writing some kind of 'assembly explorer'. (i've used some portions of code from here, here and here and none of 'em gave any of expected results). But i've found a small bug: when i tried to invoke class method from assembly i've loaded, application raised MissingMethod exception. I'm sure DLL i'm loading contains class and method i'm tryin' to invoke (my app ensures me as well as RedGate's .NET Reflector): The main application code seems to be okay and i start thinking if i was wrong with my DLL... Ah, and i've put both of projects into one solution, but i don't think it may cause any troubles. And yes, DLL project has 'class library' target while the main application one has 'console applcation' target. So, the question is: what's wrong with 'em? Here are some source code: DLL source: using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace ClassLibrary1 { public class Class1 { public void Main() { System.Console.WriteLine("Hello, World!"); } } } Main application source: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Reflection; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { Assembly asm = Assembly.LoadFrom(@"a\long\long\path\ClassLibrary1.dll"); try { foreach (Type t in asm.GetTypes()) { if (t.IsClass == true && t.FullName.EndsWith(".Class1")) { object obj = Activator.CreateInstance(t); object res = t.InvokeMember("Main", BindingFlags.Default | BindingFlags.InvokeMethod, null, obj, null); // Exception is risen from here } } } catch (Exception e) { System.Console.WriteLine("Error: {0}", e.Message); } System.Console.ReadKey(); } } } UPD: worked for one case - when DLL method takes no arguments: DLL class (also works if method is not static): public class Class1 { public static void Main() { System.Console.WriteLine("Hello, World!"); } } Method invoke code: object res = t.InvokeMember("Main", BindingFlags.Default | BindingFlags.InvokeMethod, null, null, null);

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  • Is It Safe to Cast Away volatile?

    - by Yan Cheng CHEOK
    Most of the time, I am doing this way. class a { public: ~ a() { i = 100; // OK delete (int *)j; // Compiler happy. But, is it safe? // Error : delete j; } private: volatile int i; volatile int *j; }; int main() { a aa; } However, I saw an article here: https://www.securecoding.cert.org/confluence/display/seccode/EXP32-C.+Do+not+access+a+volatile+object+through+a+non-volatile+reference Casting away volatile allows access to an object through a non-volatile reference. This can result in undefined and perhaps unintended program behavior. So, what will be the workaround for my above code example?

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  • Can I use Cassandra to store objects?

    - by Sandeep
    Hi, My application works like this. A database(Mysql) where there is a command. The command is an object(consists of fields many fields like ints ans strings). There is a webservice which interact with the database and get the command from the db and performs some operation. The way how I am storing the command into db is by stripping all the fields and inserting them in to the db. Can I use cassandra in place of mysql and store the command object?

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  • Can I have fixed typed ArrayList in C#, just like C++?

    - by Kazoom
    I have an ArrayList which contains fixed type of objects. However everytime I need to extract an object a particular index, I need to typecast it to my user defined type from object type. Is there a way in C# to declare ArrayList of fixed types just like Java and C++, or is there a work around to avoid the typecasting everytime? Edit: I apologize I forgot mentioning that I require the datastructure to be thread-safe, which List is not. Otherwise I would have just used a normal Array. But I want to save myself from the effort of explicitly locking and unlocking while writing the array. So I thought of using ArrayList, synchronize it, but it requires typecasting every time.

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  • Python: Using `copyreg` to define reducers for types that already have reducers

    - by cool-RR
    (Keep in mind I'm working in Python 3, so a solution needs to work in Python 3.) I would like to use the copyreg module to teach Python how to pickle functions. When I tried to do it, the _Pickler object would still try to pickle functions using the save_global function. (Which doesn't work for unbound methods, and that's the motivation for doing this.) It seems like _Pickler first tries to look in its own dispatch for the type of the object that you want to pickle before looking in copyreg.dispatch_table. I'm not sure if this is intentional. Is there any way for me to tell Python to pickle functions with the reducer that I provide?

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  • Powershell - remote folder availability while counting files

    - by ziklop
    I´m trying to make a Powershell script that reports if there´s a file older than x minutes on remote folder. I make this: $strfolder = 'folder1 ..................' $pocet = (Get-ChildItem \\server1\edi1\folder1\*.* ) | where-object {($_.LastWriteTime -lt (Get-Date).AddDays(-0).AddHours(-0).AddMinutes(-20))} | Measure-Object if($pocet.count -eq 0){Write-Host $strfolder "OK" -foreground Green} else {Write-Host $strfolder "ERROR" -foreground Red} But there´s one huge problem. The folder is often unavailable for me bacause of the high load and I found out when there is no connection it doesn´t report an error but continues with zero in $pocet.count. It means it reports everything is ok when the folder is unavailable. I was thinking about using if(Test-Path..) but what about it became unavailable just after passing Test-Path? Does anyone has a solution please? Thank you in advance

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  • Does this simple cache class need thread synchronization?

    - by DayOne
    Does this simple cache class need thread synchronization ... if I remove the lock _syncLock statement will encounter any problems? I think i can remove the locks as the references should be updated correctly right? ... BUt i'm think whar happens if client code is iterating over the GetMyDataStructure method and it get replaced? Thanks! public sealed class Cache { private readonly object _syncLock = new object(); private IDictionary<int, MyDataStructure> _cache; public Cache() { Refresh(); } public void Refresh() { lock (_syncLock) { _cache = DAL.GetMyDataStructure(); } } public IDictionary<int, MyDataStructure> **GetMyDataStructure**() { lock (_syncLock) { return _cache; } } }

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  • Help understanding this stack trace

    - by user80632
    Hi I have health monitoring turned on, and i have the following error i'm trying to understand: Exception: Exception information: Exception type: System.InvalidCastException Exception message: Specified cast is not valid. Thread information: Thread ID: 5 Thread account name: NT AUTHORITY\NETWORK SERVICE Is impersonating: False Stack trace: at _Default.Repeater1_ItemDataBound(Object sender, RepeaterItemEventArgs e) at System.Web.UI.WebControls.Repeater.CreateControlHierarchy(Boolean useDataSource) at System.Web.UI.WebControls.Repeater.OnDataBinding(EventArgs e) at _Default.up1_Load() at _Default.Timer1_Tick(Object sender, EventArgs e) at System.Web.UI.Timer.OnTick(EventArgs e) at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) I'm just trying to figure out exactly where the problem is happening and what it is - is it happening in the Repeater1_ItemDataBound sub routine, or in the Timer1_Tick sub routine? Is the last thing that happened before the error occured at the top or bottom of the trace? any help much appreciated thanks

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  • Storing tree data in Javascript

    - by Ozh
    I need to store data to represent this: Water + Fire = Steam Water + Earth = Mud Mud + Fire = Rock The goal is the following: I have draggable HTML divs, and when <div id="Fire"> and <div id="Mud"> overlap, I add <div id="Rock"> to the screen. Ever played Alchemy on iPhone or Android? Same stuff Right now, the way I'm doing this is a JS object : var stuff = { 'Steam' : { needs: [ 'Water', 'Fire'] }, 'Mud' : { needs: [ 'Water', 'Earth'] }, 'Rock' : { needs: [ 'Mud', 'Fire'] }, // etc... }; and every time a div overlaps with another one, I traverse the object keys and check the 'needs' array. I can deal with that structure but I was wondering if I could do any better? Edit: I should add that I also need to store a few other things, like a short description or an icon name. So typicall I have Steam: { needs: [ array ], desc: "short desc", icon:"steam.png"},

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  • What do you name the "other" kind of view-model in an MVVM project?

    - by DanM
    With MVVM, I think of a view-model as a class that provides all the data and commands that a view needs to bind to. But what happens when I have a database entity object, say a Customer, and I want to build a class that shapes or flattens the Customer class for use in a data grid. For example, maybe this special Customer object would have a property TotalOrders, which is actually calculated using a join with a collection of Order entities. My question is, what do I call this special Customer class? In other situations, I'd be tempted to call it a CustomerViewModel, but I feel like "overloading" the notion of a view-model like this would be confusing in an MVVM project. What would you suggest?

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  • C# Asynchronous Sockets questions.

    - by ccppjava
    Based on my reading and testing, with asynchronous sockets, the socket itself can be passed using state object (IAsyncResult result), also if store the socket as a private field, it would be captured by the callback methods. I am wondering how the IAysnResult is kepted between the BeginXXX and ReceiveXXX? It looks to me that after the BeginXXX call and the method ends, the state object would be disposed by GC if there is no reference to it. In the case of private field, how the private field is shared between threads? (As far as I know, a callback is executed using a thread from the default thread pool, which would be considered as a new thread.) Many thanks, hope the questions themselves are clear.

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  • Unable to send an associative array in JSON format in Zend to client

    - by Anorflame
    Hi, In one of my actions in a controller, I'm using the json view helper to send back a response to an ajax request. On the client side I alert the data that is passed to the success callback function. It works fine as long as the response is a number or an array with default keys. Once I try to send an associative array, it alerts with [object Object]. Server code: $childArray = array('key'=>'value'); $this->_helper->json($childArray); javascript: function displayChildren(data){ alert(data); } ... $.ajax({ url: "/po/add", dataType: "json", data: {format: "json"}, success: displayChildren }); I have no idea what am I doing wrong here, so any help would be appreciated...

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