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• Modifying a const through a non-const pointer

  - by jasonline

  I'm a bit confused what happened in the following code: const int e = 2; int* w = ( int* ) &e; // (1) cast to remove const-ness *w = 5; // (2) cout << *w << endl; // (3) outputs 5 cout << e << endl; // (4) outputs 2 cout << "w = " << w << endl; // (5) w points to the address of e cout << "&e = " << &e << endl; In (1), w points to the address of e. In (2), that value was changed to 5. However, when the values of *w and e were displayed, their values are different. But if you print value of w pointer and &e, they have the same value/address. How come e still contained 2, even if it was changed to 5? Were they stored in a separate location? Or a temporary? But how come the value pointed by w is still the address of e?

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• Why is XmlSerializer so hard to use?

  - by mafutrct

  I imagine to use XML serialization like this: class Foo { public Foo (string name) { Name1 = name; Name2 = name; } [XmlInclude] public string Name1 { get; private set; } [XmlInclude] private string Name2; } StreamWriter wr = new StreamWriter("path.xml"); new XmlSerializer<Foo>().Serialize (wr, new Foo ("me")); But this does not work at all: XmlSerializer is not generic. I have to cast from and to object on (de)serialization. Every property has to be fully public. Why aren't we just using Reflection to access private setters? Private fields cannot be serialized. I'd like to decorate private fields with an attribute to have XmlSerializer include them. Did I miss something and XmlSerializer is actually offering the described possibilities? Are there alternate serializers to XML that handle these cases more sophisticatedly? If not: We're in 2010 after all, and .NET has been around for many years. XML serialization is often used, totally standard and should be really easy to perform. Or is my understanding possibly wrong and XML serialization ought not to expose the described features for a good reason? (Feel free to adjust caption or tags. If this should be CW, please just drop a note.)

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• Validating Application Settings Key Values in Isolated Storage for Windows Phone Applications

  - by Martin Anderson

  Hello everyone. I am very new at all this c# Windows Phone programming, so this is most probably a dumb question, but I need to know anywho... IsolatedStorageSettings appSettings = IsolatedStorageSettings.ApplicationSettings; if (!appSettings.Contains("isFirstRun")) { firstrunCheckBox.Opacity = 0.5; MessageBox.Show("isFirstRun not found - creating as true"); appSettings.Add("isFirstRun", "true"); appSettings.Save(); firstrunCheckBox.Opacity = 1; firstrunCheckBox.IsChecked = true; } else { if (appSettings["isFirstRun"] == "true") { firstrunCheckBox.Opacity = 1; firstrunCheckBox.IsChecked = true; } else if (appSettings["isFirstRun"] == "false") { firstrunCheckBox.Opacity = 1; firstrunCheckBox.IsChecked = false; } else { firstrunCheckBox.Opacity = 0.5; } } I am trying to firstly check if there is a specific key in my Application Settings Isolated Storage, and then wish to make a CheckBox appear checked or unchecked depending on if the value for that key is "true" or "false". Also I am defaulting the opacity of the checkbox to 0.5 opacity when no action is taken upon it. With the code I have, I get the warnings Possible unintended reference comparison; to get a value comparison, cast the left hand side to type 'string' Can someone tell me what I am doing wrong. I have explored storing data in an Isolated Storage txt file, and that worked, I am now trying Application Settings, and will finally try to download and store an xml file, as well as create and store user settings into an xml file. I want to try understand all the options open to me, and use which ever runs better and quicker

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• How to use Common Table Expression and check no duplication in sqlserver

  - by vodkhang

  I have a table references to itself. User table: id, username, managerid and managerid links back to id Now, I want to get all the managers including direct manager, manager of direct manager, so on and so forth... The problem is that I do not want to have a unstop recursive sql. So, I want to check if an id alreay in a list, I will not include it anymore. Here is my sql for that: with --the relation for all the subparts of ozsolar including itself all_managers (id, username, managerid, idlist) as ( --seed that is the ozsola part select u1.id, u1.username, u1.managerid, ' ' from users u1, users u2 where u1.id = u2.managerid and u2.id = 6 UNION ALL select u.id, u.username, u.managerid, idlist + ' ' + u.id from all_managers a, users u where a.managerid = u.id and charindex(cast(u.id as nvarchar(5)), idlist) != 0 ) --select the total number of subparts and group by subpart select id, username from all_managers; The problem is that in this line: select u1.id, u1.username, u1.managerid, ' ' The sqlserver complains with me that I can not put ' ' as the initialized for idlist. nvarchar(40) does not work as well. I do not know how to declare it inside a common table expression like this one. Usually, in db2, I can just put varchar(40)

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• Reference-type conversion operators: asking for trouble?

  - by Ben

  When I compile the following code using g++ class A {}; void foo(A&) {} int main() { foo(A()); return 0; } I get the following error messages: > g++ test.cpp -o test test.cpp: In function ‘int main()’: test.cpp:10: error: invalid initialization of non-const reference of type ‘A&’ from a temporary of type ‘A’ test.cpp:6: error: in passing argument 1 of ‘void foo(A&)’ After some reflection, these errors make plenty of sense to me. A() is just a temporary value, not an assignable location on the stack, so it wouldn't seem to have an address. If it doesn't have an address, then I can't hold a reference to it. Okay, fine. But wait! If I add the following conversion operator to the class A class A { public: operator A&() { return *this; } }; then all is well! My question is whether this even remotely safe. What exactly does this point to when A() is constructed as a temporary value? I am given some confidence by the fact that void foo(const A&) {} can accept temporary values according to g++ and all other compilers I've used. The const keyword can always be cast away, so it would surprise me if there were any actual semantic differences between a const A& parameter and an A& parameter. So I guess that's another way of asking my question: why is a const reference to a temporary value considered safe by the compiler whereas a non-const reference is not?

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• How to access generic property without knowing the closed generic type

  - by Martin Booka Weser

  I have a generic Type as follows public class TestGeneric<T> { public T Data { get; set; } public TestGeneric(T data) { this.Data = data; } } If i have now an object (which is coming from some external source) from which i know that it's type is of some closed TestGeneric<, but i don't know the TypeParameter T. Now I need to access the Data of my object. Problem is that i can't cast the object, since i don't know exactly to which closed TestGeneric. I use // thx to http://stackoverflow.com/questions/457676/c-reflection-check-if-a-class-is-derived-from-a-generic-class private static bool IsSubclassOfRawGeneric(Type rawGeneric, Type subclass) { while (subclass != typeof(object)) { var cur = subclass.IsGenericType ? subclass.GetGenericTypeDefinition() : subclass; if (rawGeneric == cur) { return true; } subclass = subclass.BaseType; } return false; } to make sure, my object is of the generic type. The code in question is as follows: public static void Main() { object myObject = new TestGeneric<string>("test"); // or from another source if (IsSubclassOfRawGeneric(typeof(TestGeneric<>), myObject.GetType())) { // the following gives an InvalidCastException // var data = ((TestGeneric<object>)myObject).Data; // if i try to access the property with reflection // i get an InvalidOperationException var dataProperty = typeof(TestGeneric<>).GetProperty("Data"); object data = dataProperty.GetValue(myObject, new object[] { }); } } I need the Data regardless of its type (well, if i could ask for its type using GetType() would be fine, but not necessary) since i just want to dump it in xml using ToString(). Any suggestions? Thanx.

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• Why ClassCastException on JMS ConnectionFactory lookup in JNDI?

  - by Derek Mahar

  What might be the cause of the following ClassCastException in a standalone JMS client application when it attempts to retrieve a connection factory from the JNDI provider? Exception in thread "main" java.lang.ClassCastException: javax.naming.Reference cannot be cast to javax.jms.ConnectionFactory Here is an abbreviated version of the JMS client that includes only its start() and stop() methods. The exception occurs on the first line in method start() which attempts to retrieve the connection factory from the JNDI provider, a remote LDAP server. The JMS connection factory and destination objects are on a remote JMS server. class JmsClient { private ConnectionFactory connectionFactory; private Connection connection; private Session session; private MessageConsumer consumer; private Topic topic; public void stop() throws JMSException { consumer.close(); session.close(); connection.close(); } public void start(Context context, String connectionFactoryName, String topicName) throws NamingException, JMSException { // ClassCastException occurs when retrieving connection factory. connectionFactory = (ConnectionFactory) context.lookup(connectionFactoryName); connection = connectionFactory.createConnection("username","password"); session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE); topic = (Topic) context.lookup(topicName); consumer = session.createConsumer(topic); connection.start(); } private static Context getInitialContext() throws NamingException, IOException { String filename = "context.properties"; Properties props = new Properties(); props.load(new FileInputStream(filename)); return new InitialContext(props); } }

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• Can't get SFTP to work in PHP

  - by Chris Kloberdanz

  I am writing a simple SFTP client in PHP because we have the need to programatically retrieve files via n remote servers. I am using the PECL SSH2 extension. I have run up against a road block, though. The documentation on php.net suggests that you can do this: $stream = fopen("ssh2.sftp://$sftp/path/to/file", 'r'); However, I have an ls method that attempts to something similar public function ls($dir) { $rd = "ssh2.sftp://{$this->sftp}/$dir"; $handle = opendir($rd); if (!is_resource($handle)) { throw new SFTPException("Could not open directory."); } while (false !== ($file = readdir($handle))) { if (substr($file, 0, 1) != '.'){ print $file . "\n"; } } closedir($handle); } I get the following error: PHP Warning: opendir(): Unable to open ssh2.sftp://Resource id #5/outgoing on remote host This makes perfect sense because that's what happens when you cast a resource to string. Is the documentation wrong? I tried replacing the resource with host, username, and host and that didn't work either. I know the path is correct because I can run SFTP from the command line and it works fine. Has anyone else tried to use the SSH2 extenstion with SFTP? Am I missing something obvious here? UPDATE: I setup sftp on another machine in-house and it works just fine. So, there must be something about the server I am trying to connect to that isn't working.

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• How can I read a DBF file with incorrectly defined column data types using ADO.NET?

  - by Jason

  I have a several DBF files generated by a third party that I need to be able to query. I am having trouble because all of the column types have been defined as characters, but the data within some of these fields actually contain binary data. If I try to read these fields using an OleDbDataReader as anything other than a string or character array, I get an InvalidCastException thrown, but I need to be able to read them as a binary value or at least cast/convert them after they are read. The columns that actually DO contain text are being returned as expected. For example, the very first column is defined as a character field with a length of 2 bytes, but the field contains a 16-bit integer. I have written the following test code to read the first column and convert it to the appropriate data type, but the value is not coming out right. The first row of the database has a value of 17365 (0x43D5) in the first column. Running the following code, what I end up getting is 17215 (0x433F). I'm pretty sure it has to do with using the ASCII encoding to get the bytes from the string returned by the data reader, but I'm not sure of another way to get the value into the format that I need, other that to write my own DBF reader and bypass ADO.NET altogether which I don't want to do unless I absolutely have to. Any help would be greatly appreciated. byte[] c0; int i0; string con = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\ASTM;Extended Properties=dBASE III;User ID=Admin;Password=;"; using (OleDbConnection c = new OleDbConnection(con)) { c.Open(); OleDbCommand cmd = c.CreateCommand(); cmd.CommandText = "SELECT * FROM astm2007"; OleDbDataReader dr = cmd.ExecuteReader(); while (dr.Read()) { c0 = Encoding.ASCII.GetBytes(dr.GetValue(0).ToString()); i0 = BitConverter.ToInt16(c0, 0); } dr.Dispose(); }

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• How to call a .NET COM method with an array from delphi using PSafeArray?

  - by Sebastian Godelet

  Hello. I have an .NET (4.0) interface which is implemented with a ServicedComponent COM+ class: interface DotNetIface { void MethodRef(var System.Guid guid); void MethodArray(System.Guid[] guids, params object[] parameters); void MethodCStyle([MarshalAs(UnmanagedType.LPArray, ArraySubType=UnmanagedType.Struct, SizeConst=5)]System.Guid[] guids); } Now I used the Delphi 2007 import wizard to import the type library, and as expected I get the following signatures: procedure MethodRef(var guid : TGuid); procedure MethodArray(guids : PSafeArray); procedure MethodCStyle(var guids : ClrGuid /* from mscorlib_TLB */); If i now call the "ref" method like this it works fine: procedure CallByRef(guid : TGuid); var test : TGuid; begin test := ... comRef.MethodRef(guid); end; Now I also need the array method procedure CallArray(); var localGuid : TGuid; arrayVariant : OleVariant; begin arrayVariant := VarArrayCreate([0,4], varVariant /* dont know here */); arrayVariant[0] := localGuid; /* compile error, cannot cast implicitly */ comRef.MethodArray(PSafeArray(TVarData(arrayVariant.VArray)), /* here this object... PSafeArray works actually*/); end; Now lastly i tried with a c array procedure CallCStyle(); var localGuid : TGuid; arrayOfGuid : array [0..4] of ClrGuid; begin arrayOfGuid[0] := ClrGuid(localGuid); comRef.MethodCStyle(PSafeArray(/* now i dont know put it*/, /* here this object... PSafeArray works actually*/); end; I seriously dont know how to make this work. I hope someone has more experience with COM marshalling thx Side node: I found VT_CLSID which i think can be passed for SafeArrayCreate, but I am not sure how to sue that

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• SQL Server: Is it possible to prevent SQL Agent from failing a step on error?

  - by Kenneth

  I have a stored procedure that runs custom backups for around 60 SQL servers (mixes 2000 through 2008R2). Occasionally, due to issues outside of my control (backup device inaccessible, network error, etc.) an individual backup on one or two databases will fail. This causes this entire step to fail, which means any subsequent backup commands are not executed and half of the databases on a given server may not be backed up. On the 2005+ boxes I am using TRY/CATCH blocks to manage these problems and continue backing up the remaining databases. On a 2000 server however, for example, I have no way to prevent this error from failing the entire step: Msg 3201, Level 16, State 1, Line 1 Cannot open backup device 'db-diff(\PATH\DB-DIFF-03-16-2010.DIF)'. Operating system error 5(Access is denied.). Msg 3013, Level 16, State 1, Line 1 BACKUP DATABASE is terminating abnormally. I am simply asking if anything like TRY/CATCH is possible in SQL 2000? I realize there are no built in methods for this, so I guess I am looking for some creativity. Even when wrapping each backup (or any failing statement) via sp_executesql the job fails instantly. Example: DECLARE @x INT, @iReturn INT PRINT 'Executing statement that will fail with 208.' EXEC @iReturn = Sp_executesql N'SELECT * from TABLETHATDOESNTEXIST;' PRINT Cast(@iReturn AS NVARCHAR) --In SSMS this return code prints. Executed as a job it fails and aborts before this statement.

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• Calling MethodBase's Invoke on a constructor (reflection)

  - by Alix

  Hi everyone. First of all, sorry if this has been asked before. I've done a pretty comprehensive search and found nothing quite like it, but I may have missed something. And now to the question: I'm trying to invoke a constructor through reflection, with no luck. Basically, I have an object that I want to clone, so I look up the copy constructor for its type and then want to invoke it. Here's what I have: public Object clone(Object toClone) { MethodBase copyConstructor = type.GetConstructor( new Type[] { toClone.GetType() }); return method.Invoke(toClone, new object[] { toClone }); //<-- doesn't work } I call the above method like so: List list = new List(new int[] { 0, 1, 2 }); List clone = (List) clone(list); Now, notice the invoke method I'm using is MethodBase's invoke. ConstructorInfo provides an invoke method that does work if invoked like this: return ((ConstructorInfo) method).Invoke(new object[] { toClone }); However, I want to use MethodBase's method, because in reality instead of looking up the copy constructor every time I will store it in a dictionary, and the dictionary contains both methods and constructors, so it's a Dictionary<MethodBase>, not Dictionary<ConstructorInfo>. I could of course cast to ConstructorInfo as I do above, but I'd rather avoid the casting and use the MethodBase method directly. I just can't figure out the right parameters. Any help? Thanks so much.

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• Lazy non-modifiable list in Google Collections

  - by mindas

  I was looking for a decent implementation of a generic lazy non-modifiable list implementation to wrap my search result entries. The unmodifiable part of the task is easy as it can be achieved by Collections.unmodifiableList() so I only need to sort out the the lazy part. Surprisingly, google-collections doesn't have anything to offer; while LazyList from Apache Commons Collections does not support generics. I have found an attempt to build something on top of google-collections but it seems to be incomplete (e.g. does not support size()), outdated (does not compile with 1.0 final) and requiring some external classes, but could be used as a good starting point to build my own class. Is anybody aware of any good implementation of a LazyList? If not, which option do you think is better: write my own implementation, based on google-collections ForwardingList, similar to what Peter Maas did; write my own wrapper around Commons Collections LazyList (the wrapper would only add generics so I don't have to cast everywhere but only in the wrapper itself); just write something on top of java.util.AbstractList; Any other suggestions are welcome.

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• How to get rid of void-pointers.

  - by Patrick

  I inherited a big application that was originally written in C (but in the mean time a lot of C++ was also added to it). Because of historical reasons, the application contains a lot of void-pointers. Before you start to choke, let me explain why this was done. The application contains many different data structures, but they are stored in 'generic' containers. Nowadays I would use templated STL containers for it, or I would give all data structures a common base class, so that the container can store pointers to the base class, but in the [good?] old C days, the only solution was to cast the struct-pointer to a void-pointer. Additionally, there is a lot of code that works on these void-pointers, and uses very strange C constructions to emulate polymorphism in C. I am now reworking the application, and trying to get rid of the void-pointers. Adding a common base-class to all the data structures isn't that hard (few days of work), but the problem is that the code is full of constructions like shown below. This is an example of how data is stored: void storeData (int datatype, void *data); // function prototype ... Customer *myCustomer = ...; storeData (TYPE_CUSTOMER, myCustomer); This is an example of how data is fetched again: Customer *myCustomer = (Customer *) fetchData (int datatype, char *key); I actually want to replace all the void-pointers with some smart-pointer (reference-counted), but I can't find a trick to automate (or at least) help me to get rid of all the casts to and from void-pointers. Any tips on how to find, replace, or interact in any possible way with these conversions?

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• Retrive data from two tables in asp.net mvc using ADO.Net Entity Framework

  - by user192972

  Please read my question carefully and reply me. I have two tables as table1 and table2. In table1 i have columns as AddressID(Primary Key),Address1,Address2,City In table2 i have columns as ContactID(Primary Key),AddressID(Foriegn Key),Last Name,First Name. By using join operation i can retrive data from both the tables. I created a Model in my MVC Application.I can see both the tables in enitity editor. In the ViewData folder of my solution explorer i created two class as ContactViewData.cs and SLXRepository.cs In the ContactViewData.cs i have following code public IEnumerable<CONTACT> contacts { get; set; } In the SLXRepository.cs i have following code public IEnumerable<CONTACT> GetContacts() { var contact = ( from c in context.CONTACT join a in context.ADDRESS on c.ADDRESSID equals a.ADDRESSID select new { a.ADDRESS1, a.ADDRESS2, a.CITY, c.FIRSTNAME, c.LASTNAME } ); return contact; } I am getting the error in return type Cannot implicitly convert type 'System.Linq.IQueryable' to 'System.Collections.Generic.IEnumerable'. An explicit conversion exists (are you missing a cast?)

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• Using MinHash to find similiarities between 2 images

  - by Sung Meister

  I am using MinHash algorithm to find similar images between images. I have run across this post, How can I recognize slightly modified images? which pointed me to MinHash algorithm. Being a bit mathematically challenged, I was using a C# implementation from this blog post, Set Similarity and Min Hash. But while trying to use the implementation, I have run into 2 problems. What value should I set universe value to? When passing image byte array to HashSet, it only contains distinct byte values; thus comparing values from 1 ~ 256. What is this universe in MinHash? And what can I do to improve the C# MinHash implementation? Since HashSet<byte> contains values upto 256, similarity value always come out to 1. Here is the source that uses the C# MinHash implementation from Set Similarity and Min Hash: class Program { static void Main(string[] args) { var imageSet1 = GetImageByte(@".\Images\01.JPG"); var imageSet2 = GetImageByte(@".\Images\02.TIF"); //var app = new MinHash(256); var app = new MinHash(Math.Min(imageSet1.Count, imageSet2.Count)); double imageSimilarity = app.Similarity(imageSet1, imageSet2); Console.WriteLine("similarity = {0}", imageSimilarity); } private static HashSet<byte> GetImageByte(string imagePath) { using (var fs = new FileStream(imagePath, FileMode.Open, FileAccess.Read)) using (var br = new BinaryReader(fs)) { //List<int> bytes = br.ReadBytes((int)fs.Length).Cast<int>().ToList(); var bytes = new List<byte>(br.ReadBytes((int) fs.Length).ToArray()); return new HashSet<byte>(bytes); } } }

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• Design considerations for temporarily transforming a player into an animal in a role playing game

  - by mikedev

  I am working on a role playing game for fun and to practice design patterns. I would like players to be able to transform themselves into different animals. For example, a Druid might be able to shape shift into a cheetah. Right now I'm planning on using the decorator pattern to do this but my question is - how do I make it so that when a druid is in the cheetah form, they can only access skills for the cheetah? In other words, they should not be able to access their normal Druid skills. Using the decorator pattern it appears that even in the cheetah form my druid will be able to access their normal druid skills. class Druid : Character { // many cool druid skills and spells void LightHeal(Character target) { } } abstract class CharacterDecorator : Character { Character DecoratedCharacter; } class CheetahForm : CharacterDecorator { Character DecoratedCharacter; public CheetahForm(Character decoratedCharacter) { DecoratedCharacter= decoratedCharacter; } // many cool cheetah related skills void CheetahRun() { // let player move very fast } } now using the classes Druid myDruid = new Druid(); myDruid.LightHeal(myDruid); // casting light heal here is fine myDruid = new CheetahForm(myDruid); myDruid.LightHeal(myDruid); // casting here should not be allowed Hmmmm...now that I think about it, will myDruid be unable to us the Druid class spells/skills unless the class is down-casted? But even if that's the case, is there a better way to ensure that myDruid at this point is locked out from all Druid related spells/skills until it is cast back to a Druid (since currently it's in CheetahForm)

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• Converting an integer to a boxed enum type only known at runtime

  - by Marc Gravell

  Imagine we have an enum: enum Foo { A=1,B=2,C=3 } If the type is known at compile-time, a direct cast can be used to change between the enum-type and the underlying type (usually int): static int GetValue() { return 2; } ... Foo foo = (Foo)GetValue(); // becomes Foo.B And boxing this gives a box of type Foo: object o1 = foo; Console.WriteLine(o1.GetType().Name); // writes Foo (and indeed, you can box as Foo and unbox as int, or box as int and unbox as Foo quite happily) However (the problem); if the enum type is only known at runtime things are... trickier. It is obviously trivial to box it as an int - but can I box it as Foo? (Ideally without using generics and MakeGenericMethod, which would be ugly). Convert.ChangeType throws an exception. ToString and Enum.Parse works, but is horribly inefficient. I could look at the defined values (Enum.GetValues or Type.GetFields), but that is very hard for [Flags], and even without would require getting back to the underlying-type first (which isn't as hard, thankfully). But; is there a more direct to get from a value of the correct underlying-type to a box of the enum-type, where the type is only known at runtime?

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• Mapping self-table one-to-many using non-PK clolumns

  - by Harel Moshe

  Hey, i have a legacy DB to which a Person object is mapped, having a collection of family-members, like this: class Person { ... string Id; /* 9-digits string */ IList<Person> Family; ... } The PERSON table seems like: Id: CHAR(9), PK FamilyId: INT, NOT NULL and several other non-relevant columns. I'm trying to map the Family collection to the PERSON table using the FamilyId column, which is not the PK as mentioned above. So, i actually have a one-to-many which is self-table-referential. I'm getting an error saying 'Cast is not valid' when my mapping looks like this: ... <set name="Family" table="Person" lazy="false"> <key column="FamilyId" /> <one-to-many class="Person" /> </set> ... because obviously, the join NHibernate is trying to make is between the PK column, Id, and the 'secondary' column, FamilyId, instead of joining the FamilyId column to itself. Any ideas please?

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• How to put foreign key constraints on a computed fields in sql server?

  - by Asaf R

  Table A has a computed field called Computed1. It's persisted and not null. Also, it always computes to an expression which is char(50). It's also unique and has a unique key constraint on it. Table B has a field RefersToComputed1, which should refer to a valid Computed1 value. Trying to create a foreign key constraint on B's RefersToComputed1 that references A' Computed1 leads to the following error: Error SQL01268: .Net SqlClient Data Provider: Msg 1753, Level 16, State 0, Line 1 Column 'B.RefersToComputed1' is not the same length or scale as referencing column 'A.Computed1' in foreign key 'FK_B_A'. Columns participating in a foreign key relationship must be defined with the same length and scale. Q: Why is this error created? Are there special measures needed for foreign keys for computed columns, and if so what are they? Summary: The specific problem rises from computed, char based, fields being varchar. Hence, Computed1 is varchar(50) and not char(50). It's best to have a cast surrounding a computed field's expression to force it to a specific type. Credit goes to Cade Roux for this tip.

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• Accessing dynamically added control from GridView Footer row

  - by harold-sota

  Hi, I have GridView control in my asp.net page with auto generated fields there is only footer template is present under asp:TemplateField. I can bind this gridview with any of databae table as depend on user selection. Now want to add new record in database so I have added text boxes on footer template cells at runtime depend on number of columns on table. But when I accessing these text boxes from footer template on gridview_RowCommand event its not retriving textbox control. this is the code SGridView.ShowFooter = True For i As Integer = 0 To ctrList.Count Dim ctr As Control = CType(ctrList.Item(i), Control) SGridView.FooterRow.Cells(i + 1).Controls.Add(ctr) Next the ctrList contain Controls textBox, checkbox dropdowlist ect. there is all ok but when i wont to get the text or value or checked value of controls i cant cast the controls in rowcommand event Here is the code: Protected Sub SGridView_RowCommand(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewCommandEventArgs) Handles SGridView.RowCommand If e.CommandName = "Add" Then Dim ctrList As ControlCollection = SGridView.FooterRow.Controls For Each ctr As Control In ctrList If TypeOf ctr Is TextBox Then Dim name As TextBox = CType(ctr, TextBox) Dim val As String = name.Text End If Next End If this excample is for the textBox control. Plese suggest me how can I get footer control textboxes. So that I can save data in database.

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• handling DATETIME values 0000-00-00 00:00:00 in JDBC

  - by Jason S

  I get an exception (see below) if I try to do resultset.getString("add_date"); for a JDBC connection to a MySQL database containing a DATETIME value of 0000-00-00 00:00:00 (the quasi-null value for DATETIME), even though I'm just trying to get the value as string, not as an object. I got around this by doing SELECT CAST(add_date AS CHAR) as add_date which works, but seems silly... is there a better way to do this? My point is that I just want the raw DATETIME string, so I can parse it myself as is. note: here's where the 0000 comes in: (from http://dev.mysql.com/doc/refman/5.0/en/datetime.html) Illegal DATETIME, DATE, or TIMESTAMP values are converted to the “zero” value of the appropriate type ('0000-00-00 00:00:00' or '0000-00-00'). The specific exception is this one: SQLException: Cannot convert value '0000-00-00 00:00:00' from column 5 to TIMESTAMP. SQLState: S1009 VendorError: 0 java.sql.SQLException: Cannot convert value '0000-00-00 00:00:00' from column 5 to TIMESTAMP. at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1055) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:926) at com.mysql.jdbc.ResultSetImpl.getTimestampFromString(ResultSetImpl.java:6343) at com.mysql.jdbc.ResultSetImpl.getStringInternal(ResultSetImpl.java:5670) at com.mysql.jdbc.ResultSetImpl.getString(ResultSetImpl.java:5491) at com.mysql.jdbc.ResultSetImpl.getString(ResultSetImpl.java:5531)

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• Generic list typecasting problem

  - by AJ

  Hello, I'm new to C# and am stuck on the following. I have a Silverlight web service that uses LINQ to query a ADO.NET entity object. e.g.: [OperationContract] public List<Customer> GetData() { using (TestEntities ctx = new TestEntities()) { var data = from rec in ctx.Customer select rec; return data.ToList(); } } This works fine, but what I want to do is to make this more abstract. The first step would be to return a List<EntityObject> but this gives a compiler error, e.g.: [OperationContract] public List<EntityObject> GetData() { using (TestEntities ctx = new TestEntities()) { var data = from rec in ctx.Customer select rec; return data.ToList(); } } The error is: Error 1 Cannot implicitly convert type 'System.Collections.Generic.List<SilverlightTest.Web.Customer>' to 'System.Collections.Generic.IEnumerable<System.Data.Objects.DataClasses.EntityObject>'. An explicit conversion exists (are you missing a cast?) What am i doing wrong? Thanks, AJ

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• Converting an int64 value to a Number object in JavaScript

  - by Matt

  I have a COM object which has a method that returns an unsigned int64 (VT_UI8) value. We have an HTML page which contains some JavaScript which can load the COM object and make the call to that method, to retrieve the value as such: var foo = MyCOMObject.GetInt64Value(); This value can easily be displayed to the user in a message dialog using: alert(foo); or displayed on the page by: document.getElementById('displayToUser').innerHTML = foo; However, we cannot use this value as a Number (e.g. if we try to multiply it by 2) without the page throwing "Number expected" errors. If we check "typeof(foo)" it returns "unknown". I've found a workaround for this by doing the following: document.getElementById('displayToUser').innerHTML = foo; var bar = parseInt(document.getElementById('displayToUser').innerHTML); alert(bar*2); What I need to know is how to make that process more efficient. Specifically, is there a way to cast foo to a String explicitly, rather than having to set some document element's innerHTML to foo and then retrieve it from that. I wouldn't mind calling something like: alert(parseInt((string)foo) * 2); Even better would be if there is a way to directly convert the int64 to a Number, without going through the String conversion, but I hold out less hope for that.

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• c# scope/typing/assignment question

  - by Shannow

  Hi there another quick question. I would like to create a variable object so that depending on the value of something, it gets cast as needed. e.g. var rule; switch (seqRuleObj.RuleType) { case SeqRuleObj.type.Pre : rule = new preConditionRuleType(); rule = (preConditionRuleType)seqRuleObj.Rule; break; case SeqRuleObj.type.Post : rule = new postConditionRuleType(); rule = (postConditionRuleType)seqRuleObj.Rule; break; case SeqRuleObj.type.Exit : rule = new exitConditionRuleType(); rule = (exitConditionRuleType)seqRuleObj.Rule; break; default : break; } String result; foreach (sequencingRuleTypeRuleConditionsRuleCondition cond in rule.ruleConditions.ruleCondition) { ....../ blah } so basically this will not work. c# will not allow me to create an new object in every case as the name is aleady defined. i can just paste the foreach loop into each case but that to me is such a waste, as the objects are exactly the same in all but name.

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