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Visual C# Language

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  - 1
    - creating arrays Your database approach calls for more flexibility than the array allows for, and it seems you don't know about the arraylist. It's inconvienent that you still use .NET 1.1, as generics in .NET 2.0 would provide substantial benefits for such and any future requirement. Anyway, a class for holding student info could look something like this: public class Student { string name; string email; string course; // Default constructor: public Student() { } // Custom constructor: public Student(string name, string email, string course) { this.name = name; this.email = email; this.course = course; } public string Name { get { return name; } set { name = value; } } public string Email { get { return email; } set { email = value; } } public string Course { get { return course} set { course = value; } } } For the "database", instead of using an array I would use an ArrayList (contained in the System.Collections namespace). However, this is not parameterized, meaning that you can store any type of object in it, which can, and will, lead to disastrous bugs eventually. Hence, I would derive from the class and override some of the methods to make absolutely sure you cannot store anything other than student object in it: public class StudentList : ArrayList { public StudentList () : base() { } public StudentList (int capacity) : base(capacity) { } public StudentList (ICollection c) : base(c) { // This is really bad because we don't get notified before after the elements in the collection are added to the list, but we get the exception anyway: foreach (object o in c) { if (!(o is Student)) throw new ArgumentException("One or more of the objects are incompatible."); } } public override int Add(object value) { if (value is Student) return base.Add(value); else throw new ArgumentException("The object is incompatible."); } public override void AddRange(ICollection c) { foreach (object o in c) { if (!(o is Student)) throw new ArgumentException("One or more of the objects are incompatible."); } base.AddRange(c); } public override Student this[int index] { get { return (Student)(base[index]); } set { base[index] = value; } } } Of course, more methods could be overriden to ensure better type safety, but this is the least you must do. Whenever you want a list that can store up to 50 students without resizing its internal array, simply write: StudentList sl = new StudentList(50); To access items in the list, just do as with any array, however you'll have to cast to Student: Student s = sl[4]; As you see, it gets pretty messed up without generics, and there's a lot more traps to be aware of, but I think this could help you for a start. Tag: Visual C# Language Casting question Visual C#
  - 2
    - Is is possible to do it in C#? May I know how to convert the following PHP code to C# I hope some C# experts can help here, thank you! Code Snippet $tmp = substr(chunk_split('1234123412341234', 1, ':'), 0, -1); $Split = split('[:]' , $tmp); $First[1] = $Split[0]; $First[2] = $Split[4]; $First[3] = $Split[8]; <---------this is be 8 $First[4] = $Split[12]; $Change = 0; while ($Change < 4) { $Change = $Change + 1; if ($First[$Change] > 0) { $First[$Change] = $First[$Change] - 1; } else { $First[$Change] = 9; } } $Split[0] = $First[1]; $Split[4] = $First[2]; $Split[8] = $First[3]; <---------this is be 8 $Split[12] = $First[4]; $Count = 0; $CC = ''; while ($Count < count($Split)) { $CC .= $Split[$Count]; $Count = $Count + 1; } Please advise (Moderator Use the code block button by highlighting text then select {} button) Tag: Visual C# Language Casting question Visual C#
  - 3
    - Variable scope ina foreach loop Hi, I get a compiler error when I declare a variable of the same name as the one declared in a foreach loop as the code snippet below shows: foreach ( FileInfo file in sourceDir.GetFiles()) { ...} FileInfo file = testDir.GetFiles()[0]; The error is: "A local variable named 'file' cannot be declared in this scope because it would give a different meaning to 'file', which is already used in a 'child' scope to denote something else" I dont see why this is a problem if the two fiel variables are in different scopes or am I wrong in that assumption If not, then why do I alse get a compiler error if I try to reuse the variable by changing the second line to: file = testDir.GetFiles()[0]; Thanks Tag: Visual C# Language Casting question Visual C#
  - 4
    - blocking 2 of the same exe's from runing You need to use win32 interop, [DllImport("user32.dll")]public static extern int FindWindow(string lpClassName, string lpWindowName); [DllImport("user32.dll")]public static extern int SendMessage(int hWnd, int msg, int wParam, int lParam); If you only need to access the main application window, those two methods will surfice, if you need access to child window you will also need : [DllImport("user32.dll")]public static extern bool EnumChildWindows(int hWnd, Delegate lpEnumFunc, int lParam); Which works with a call back (lpEnumFunc) and passes the Hwnd of each child of the Hwnd past into it, one by one. To maximise the main window of an application you first need to obtain its handle, then you need to send it the maximise message, an untested example follows: //you need to have the import methods and these two constants available const int WM_SYSCOMMAND = 0x0112; const int SC_MAXIMIZE = 0xF030 //get the window handle int hWnd = FindWindow("The Class ie MyApplication","The name or blank for topmost"); if(hWnd > -1)//if we have a handle, send it the maximize message SendMessage(hWnd, WM_SYSCOMMAND, SC_MAXIMIZE, 0); Regards Tag: Visual C# Language Casting question Visual C#
  - 5
    - moving auto generated event handlers? Adam Bretz wrote: You could make the frmMain.cs a partial class. Implement all the logic in one part and all the events in another. I don't know how the IDE will react to that, but it will at least keep the file shorter. Hope this helps. Thanks, that's what I'm doing now. frmMain is already a partial class when the IDE is used to add a new form so that part is already taken care of for me. It's just that even with event handlers alone, some form files get quite large. Steve Tag: Visual C# Language Casting question Visual C#
  - 6
    - How to make a program unstoppable immrtfoo wrote: No offense but it seems like a key logger or something It has nothing to do with a keylogger. I just need a windows form to pop up when Windows starts. I know I can add it to the Startup directory as well but it is crucial to make the form start really early and keep it running with no GUI visible except on the notification area. I just want it not to be stopped by the limited user. How can I prevent it Tag: Visual C# Language Casting question Visual C#
  - 7
    - How to determine is there any data stored on the clipboard in C#? Hello Vincent, I would like to suggest you refer to this MSDN document. How to: Retrieve Data from the Clipboard To determine whether the Clipboard contains data in a particular format, use one of the Contains Format methods or the GetData method. To retrieve data from the Clipboard, use one of the Get Format methods or the GetData method. e.g. if (Clipboard.GetData(DataFormats.Text) != null) MessageBox.Show("Text Data stored"); else MessageBox.Show("Null"); Best Regards, Martin Xie Tag: Visual C# Language Casting question Visual C#
  - 8
    - How to separate logic from GUI? What OmegaMan is describing is layers or tiers. The generally accepted design is an application has at least three tiers: User Interface, Data, and Business Logic. The simplest method is to simply have these tiers in logical layers--where the source code is all within one project/assembly. The drawback of that is that it's easy to get at the internal details of each layer. This increases coupling and reduces cohesiveness. The next level of abstraction is to make each layer physical, or in it's own project/assembly. This increases an layer's abilities to keep its internal information private and keep coupling to a minimum. This method still leaves the two layers coupled, i.e. the UI layer must know about the Business Logic Layer in order to instantiate it and interface with it. The next level of abstraction is what is called interface-oriented design. This means interaction between two classes is always done via an interface. The UI layer would not be directly coupled to the Business Logic Layer, it would be directly coupled to one or more interfaces that the Business Logic layer implements. The benefits of decoupling the layers like this are many. One is that a layer can be swapped out for another layer (Mocking is a common use for this) and the other layer need no recompilation. Another other benefit is that more layers can be added without another layer really caring--just as long as something is implementing the interfaces it uses. E.g. the simplest case would be a layer would implement all interfaces the GUI layer uses. The most complex would be that each interface is implemented by a different sub-layer, each in their own assembly. All these benefits stem from the lack of direct coupling. Communication between the layers would always be done through method/property calls, if the layers are physically designed, the project that needs to use those layers will need to add a reference to that assembly/project. Tag: Visual C# Language Casting question Visual C#
  - 9
    - Case of construct Wow. OmegaMan you hit the nail on the head. Can't believe you guessed it. It's actually a language called MAXScript, a script language for 3ds max, which is inspired from Lisp. In MAXScript, everything is an expression. It has really some neat features. You can check out the complete reference (grammar, features, examples, etc) by downloading the help file here (last link): http://usa.autodesk.com/adsk/servlet/index siteID=123112&id=5659551 From the help: Case Expression The case expression is used to select an expression to be evaluated from a set of labeled expressions based on a test value compared against the labels. Only the first expression whose label matches the test expression is evaluated. All labels must be comparable to the test expression. Labeled expressions can be block-expressions, so you can use the case expression as a case statement, choosing between blocks of code to execute. The syntax for <case_expr> is: case [ <expr> ] of ( <cases> ) where < expr > is the test expression and < cases > is a sequence of labeled expressions: <factor>: <expr> default : <expr> Examples new_obj = case copy_type.state of ( 2: copy $foo 3: instance $foo default: reference $foo ) A special label, default , can be optionally used to tag the expression that will be evaluated if no other labels match the test expression. If the default label is not used, and no label matches the test expression, the case expression returns a value of undefined . The labels are <factors> - elements such as number literals, name literals, string literals, variables, or block-expressions. When a case expression is evaluated, the test expression is evaluated once, then each label expression is evaluated in order until one is found that compares equally to the test expression value. The expression it labels is then evaluated and this becomes the result of the case expression. No further labels are evaluated or tested. The test expression is optional. If it is not supplied, the labels are expected to be Boolean values or expressions, and the first label evaluated as true determines the chosen case. In this variant, it is common to use expressions as labels, so be sure to parenthesize them. For example: case of ( (a > b): print "a is big" (b < c): print "b is little" (c <= d*3): ... default: ... ) Thanks, aw Tag: Visual C# Language Casting question Visual C#
  - 10
    - What [STATHREAD] do? I'm just curious what does [STATHREAD] does I understand the "THREAD" part but the "STA". What does it mean Tag: Visual C# Language Casting question Visual C#
  - 11
    - Delete a datasource Heh, I tried that now cause it seemed much easier... and it broke form designer! " The variable 'lastDiskWarningDateDataGridViewTextBoxColumn' is either undeclared or was never assigned. " can't recompile either... it was a silly sample project so it doesn't matter, plus I know how to fix it easily enough, but not the best for an excepted help method. That is one thing I left out of my method though, once you have removed the other objects, you can delete the DataSet from the solution explorer. I also assumed that the DataSource was a Database which it might well not be. -mwalts Tag: Visual C# Language Casting question Visual C#
  - 12
    - InvalidOperation Exception was unhandled hello Michael, Thanks for Reply Im not able to figure out this problem yet. Ya It is my application(my desktop application) problem not an IDE. I have used thread for different purpose. I thought the problem is due to the improper disposing of thread but I have found anything later. I tried to track the exception in call stack but when the exception occur the call stack get clear. I have also created Error log system to track the error but this error escape . I dont have any information from which line of code this error is poping out . Even at "application Close mehthod" I have dispose all the components and threads but Error is still there. I m posting the detail error information. Collection was modified; enumeration operation may not execute. at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource) at System.Collections.Generic.List`1.Enumerator.MoveNext() at System.Data.SQLite.SQLiteConnection.Close() at System.Data.SQLite.SQLiteConnection.Dispose(Boolean disposing) at System.ComponentModel.Component.Finalize() Thanks for your kind support and help. Looking forward for ur suggestion and help. best regards, Bibek Tag: Visual C# Language Casting question Visual C#
  - 13
    - Why does List<T> not implement ISerializable/IDeserializationCallback?? Thanks for the explanation Brian! However, let me try to clear up the confusion :-) When I wrote that one shouldn't serialize List<T> outside the local app domain, it wasn't for technical reasons. In fact, I was hoping the implication of my earlier statement that most serializers are capable of serializing enumerable types would point to the fact that technically speaking, it's perfectly feasible (even if the enumerable type doesn't physically implement ISerializable). However, the issue with List<T> is versioning and the lack of virtual methods that pose possible breaking changes if you have to move out of the implementation currently provided. Here's the more thorough explanation from the code analysis team blog: http://blogs.msdn.com/fxcop/archive/2006/04/27/585476.aspx Tag: Visual C# Language Casting question Visual C#
  - 14
    - instance does not exist in the current context Code Snippet SyntaxHighlightingTextBox shtb = new SyntaxHighlightingTextBox(); this is a control that was provided from an external .dll so, i added the dll into my project reference first and then, in the top of the form1.cs, i have this code: Code Snippet using SyntaxHighlighting; and iniside the form1_Load(); i have this code now: Code Snippet Controls.Add(shtb); Yet, i still get that error "The name 'shtb' does not exist in the current context" Tag: Visual C# Language Casting question Visual C#
  - 15
    - How to change Disk's volume Serial You can change the VolumeLabel of a drive by the following example...but i m not sure about volume serial System.IO. DriveInfo d = new System.IO. DriveInfo ( "E" ); d.VolumeLabel = "NewLabel" ; Tag: Visual C# Language Casting question Visual C#
  - 16
    - How can I control already open IE windows? I ended up using SendKeys and creating a new instance of IE each time a user clicks on the button. Some helpful links I came across: http://msdn2.microsoft.com/en-us/library/66ahbe6y(vs.71).aspx http://www.webtropy.com/articles/InternetExplorer.asp Internet%20explorer Tag: Visual C# Language Casting question Visual C#
- Next
  - 1
    - string to hexadecimal string Hi! I have a function i VB.net which converts a string into the ascii hex version of the characters. This functions looks like this in vb.net. Code Snippet Public Function StrToHex( ByVal str As String ) As String Dim stringPos As Integer Dim strTemp As String Dim strTemp2 As String Dim strAnswer As String = String .Empty stringPos = 1 Do While stringPos <= str.Length strTemp = Mid$(str, stringPos, 1) strTemp2 = CStr (Hex(Asc(strTemp))) If Len(strTemp2) = 1 Then strAnswer = strAnswer & "0" & strTemp2 Else strAnswer = strAnswer & strTemp2 End If stringPos = stringPos + 1 Loop StrToHex = strAnswer End Function So if send the string "3310 A" I get the result "333331302041" back. My question is how do I accomplish this in C# Many thanks in advance! Tag: Visual C# Language Casting question Visual C#
  - 2
    - config and ini??? I will suggest using application settings which comes with .NET 2.0 projects. The good thing is that you access values in typed manner using properties. You can also consider storing the values in registry for security reasons. Tag: Visual C# Language Casting question Visual C#
  - 3
    - Rotating Two Dimensional Arrays sorry, but i do not follow what you mean Tag: Visual C# Language Casting question Visual C#
  - 4
    - How can I import a c++ static library file to C# project As title Tag: Visual C# Language Casting question Visual C#
  - 5
    - Code to have a button "Paste" text into a Rich Text Box... I have a question... I am writing a HTML Editor and I was wondering if someone could tell me the code that I would enter in a button's event handler to be able to make that button "Paste" a certain code into "richTextbox1" I pretty much am looking for the button named "Form Open" to actually add the "<FORM>" tag in the Rich Text Box. I also got another question. Its similare to the above, only instead of involving a button, it involves a "Tree View". I want to be able to click down in a "Tree View" and find a certain tag like "<HTML>", and uppon double clicking on that "Tree View" button named "<HTML>" it will paste the "<HTML>" tag into "richtextBox1". Does anyone know the answer Thanks much! Landon Tag: Visual C# Language Casting question Visual C#
  - 6
    - Trying to understand IComparable Well, I gave it a little thought and I think this is the way how it goes: MyGroup executes a MyIndividual(ArrayList).Sort and therefore the operating system (OS) knows that sorting objects are of kind MyIndividual. Now the OS accesses the individual MyIndividual(ArrayList) objects at it's own (OS) algorithm. So the OS selects an MyIndividual object and executes it's associated CompareTo function. Therefore, when a CompareTo function is executed, the 'this' reference points to the MyIndividualobject that was selected by the OS before the OS called that specific CompareTo function. ;-) ;-) ;-) Regards, Henk Tag: Visual C# Language Casting question Visual C#
  - 7
    - Application settings lost upon new assembly Hi again, just to mention it works out perfectly. I still do not see the difference, if anyone can explain it that would be helpfull. Thanks a lot! Tag: Visual C# Language Casting question Visual C#
  - 8
    - memcpy to C# I need to convert the following C++ (little knowledge) method to C# (good knowledge). I am having trouble with the memcpy function. It is required here because the intial positions of the vectors must be fixed for the method to work properly. Could you kindly help with this Thank you, Drew Yallop double monte ( int n , // Number of trading opportunities double *raw , // Raw return of each int *pos , // Position of each; 1=long; -1=short; 0=neutral int nreps , // Number of replications, generally at least 1000 double *nonpar , // If not NULL, only signs used for nonparametric test int *work // Work vector n long avoids shuffling input data ) { int i, irep, k1, k2, count, nonpar_count, temp ; double cand_return, nonpar_cand_return, trial_return, prod ; memcpy ( work , pos , n * sizeof(int) ) ; // Preserve input positions /* Compute the return of the candidate model If requested, do the same for the nonparametric version */ cand_return = 0.0 ; for (i=0 ; i<n ; i++) cand_return += pos * raw ; if (nonpar != NULL) { // Do the same using only signs if requested nonpar_cand_return = 0.0 ; for (i=0 ; i<n ; i++) { prod = pos * raw ; if (prod > 0.0) nonpar_cand_return += 1.0 ; else if (prod < 0.0) nonpar_cand_return -= 1.0 ; } } /* Do the Monte-Carlo replications */ count = 0 ; // Counts how many at least as good as candidate nonpar_count = 0 ; // Ditto for ignoring signs (if requested) for (irep=0 ; irep<nreps ; irep++) { k1 = n ; // Shuffle the positions, which are in 'work' while (k1 > 1) { // While at least 2 left to shuffle k2 = (int) (unifrand () * k1) ; // Pick an int from 0 through k1-1 if (k2 >= k1) // Should never happen as long as unifrand()<1 k2 = k1 - 1 ; // But this is cheap insurance against disaster temp = work[--k1] ; // Count down k1 and swap k1, k2 entries work[k1] = work[k2] ; work[k2] = temp ; } // Shuffling is complete when this loop exits trial_return = 0.0 ; for (i=0 ; i<n ; i++) // Compute return for this randomly shuffled system trial_return += work * raw ; if (trial_return >= cand_return) // If this random system beat candidate ++count ; // Count it if (nonpar != NULL) { // Do the same using only signs if requested trial_return = 0.0 ; for (i=0 ; i<n ; i++) { // Compute return for this randomly shuffled system prod = work * raw ; if (prod > 0.0) trial_return += 1.0 ; else if (prod < 0.0) trial_return -= 1.0 ; } if (trial_return >= nonpar_cand_return) // If this random system beat candidate ++nonpar_count ; // Count it } } if (nonpar != NULL) *nonpar = (double) nonpar_count / (double) nreps ; return (double) count / (double) nreps ; } Tag: Visual C# Language Casting question Visual C#
  - 9
    - Cryptographic Exception - Length of the data to decrypt is invalid For the algorithm you chose source must be in 8 byte blocks. If it isn't then you need to pad it so it is. Otherwise the algorithm will fail. Michael Taylor - 10/26/07 http://p3net.mvps.org Tag: Visual C# Language Casting question Visual C#
  - 10
    - How to make VS 2005 IDE understand dotnet 3.0 framework? Hi Pavan, Can you see the .NET Framework 3.0 in your Current installed programs Anyway, try download and install .NET Framework 3.0 through this link: http://go.microsoft.com/fwlink/ LinkId=70848 ( http://download.microsoft.com/download/3/F/0/3F0A922C-F239-4B9B-9CB0-DF53621C57D9/dotnetfx3.exe ) To see whether it helps. Thanks Tag: Visual C# Language Casting question Visual C#
  - 11
    - Using P/Invoke to create instance of class I used Visual Studio 2005 to create a C++ Win32 project and set the Application Type to DLL and checked the Export symbols box to get a quick an dirty DLL that exports a C++ Class. I then added a private member variable of type int and added two public methods - one to set the int and one to retrieve the int value. The class looks like this... Code Snippet // This class is exported from the NativeClassExport.dll class NATIVECLASSEXPORT_API CNativeClassExport { private : int mMyInt; public : CNativeClassExport( void ); // TODO: add your methods here. int get_MyInt ( void ); void put_MyInt ( int val); }; To keep things simple (and because haven't figured out how to construct a C++ class from C# yet) I also created a factory function in the native DLL that looks like this... Code Snippet extern "C" { NATIVECLASSEXPORT_API CNativeClassExport * NativeClassExportFactory ( void ); } The implementation of the factory function looks like this Code Snippet extern "C" { NATIVECLASSEXPORT_API CNativeClassExport * NativeClassExportFactory ( void ) { return new CNativeClassExport (); } } The C# description of the factory object looks like this Code Snippet [ DllImport ( "NativeClassExport.dll" , CallingConvention = CallingConvention .Cdecl)] static extern IntPtr NativeClassExportFactory(); The C# description of the two Class methods look like this... Code Snippet [ DllImport ( "NativeClassExport.dll" , EntryPoint = " put_MyInt@CNativeClassExport@@QAEXH@Z" , CallingConvention= CallingConvention .ThisCall)] static extern void put_MyInt( IntPtr thisPtr, int val); [ DllImport ( "NativeClassExport.dll" , EntryPoint = " get_MyInt@CNativeClassExport@@QAEHXZ" , CallingConvention = CallingConvention .ThisCall)] static extern int get_MyInt( IntPtr thisPtr); To get the Entrypoint values for the methods I ran Depends against the NativeClassExport.dll file and examined the actual names of the methods. I could also have used the DumpBin utility. One downside to this approach is that the C++ decorated name of the methods can change when you recompile the DLL. If they do, then you have to re-run Depends or DumpBin and then change the EntryPoint values to match the new decorated names. You could use Ordinal rather than name to identify the entry point but Ordinals can suffer from the same problem of changing aftera recompile. With all the above a C# program can create an instance of the exported class and can call the public methods of that class... Code Snippet IntPtr theClass ; // construct the class pointer theClass = NativeClassExportFactory(); int i = 42; put_MyInt(theClass, i); int j = 0; j = get_MyInt(theClass); Console .WriteLine(j); Tag: Visual C# Language Casting question Visual C#
  - 12
    - "new"? Arguments when creating an object? (Help the beginner?) then that means this would also work instead: SomeSecondType mySecondVariable = new SomeSecondType(new SomeFirstType(a,b,c)); This is not really true in general, though there might be some cases where it is true. It would only be true if there was a signature for the constructor of SomeSecondType that had SomeFirstType as a parameter. Think of it this way... ============== Building.House myHouse = new Building.House(Color.red) ; // initialize myHouse to be a "new red house" Vehical.Car myCar = new Vehical.Car(Color.Red); // initialized myCar to be a "new red car" Building.House myHouse = new Building.House(new Vehical.Car(Color.Red)); // initialize the variable myHouse to be a "new red car house" ============== It would not likely be the case that a constructor for Building.House would take a parameter of type Car even though it might be the case that both Car and House have a constructor that was Color. Tag: Visual C# Language Casting question Visual C#
  - 13
    - Protection of C# source code it is quite good tool for obfuscation. it changes your code completly. like method names to A000001,A000002 etc and also variable names, parameters. almost every thing. if some one read assembly he does not come to know what A00001 function will do. Tag: Visual C# Language Casting question Visual C#
  - 14
    - Removing items in a list while iterating through it in your for loop, each time it iterates through, it reevaluates the list.count value. Instead of having it as: for (int i = 0; i < list.Count; i++) change it to int iCount = list.Count; for (int i = 0; i < iCount ; i++) so that list.count doesn't get changed each time you do a list.remove Tag: Visual C# Language Casting question Visual C#
  - 15
    - Microsoft.Tools.WinRes.ResourcesLoader namespace does't work with me This name space Microsoft.Tools.WinRes.ResourcesLoader I can't use it The type or namespace name 'Tools' does not exist in the namespace 'Microsoft' (are you missing an assembly reference ) this is the compiler error I need to use it how thanks Tag: Visual C# Language Casting question Visual C#
  - 16
    - How can I find whether the current thread is exited or not? if (threadMain.ThreadState != ThreadState.Running) //Not running { //Next step } OR if (!threadMain.IsAlive) //Not alive { //Next step } Does this help Tag: Visual C# Language Casting question Visual C#

Z. Margeta

Imagine the following situation.

Let's say you have a class A, which derives from IA. Let's also say that you have a collection class B which derives from IB.

IB derives from IEnumerable<IA>, and B derives from IEnumerable<A>.

Why isn't it possible to cast (IB)(B) without (implicitly) implementing the IEnumerable<IA> in B

Doesn't B implement IEnumerable<IA> implicitly since it implements IEnumerable<A> (A is derived from IA)

If you managed to stay with me this far, is there maybe a different way to do this

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Re: Visual C# Language Casting question

Peter Ritchie

Generics aren't covariant, meaning you can't cast one generic to another despite using the same templated class (generic). See http://www.fotia.co.uk/fotia/DN.01.CoVariantGenericList.aspx for an overview of Generics and covariance and the problems that would arise if you could do what you're asking to do.

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