Using weka in C#: Unable to cast object of type 'java.util.ArrayList' to type 'System.Collections.Generic.List`

问题

I am currently working on a project in which I need to use FP-Growth algorithm. I know Weka is a handy tool for it. However, I am using C# for coding (due to some other libraries I need). So, I converted weka.jar to weka.dll using IKVM.NET. Below is a code snippet that i have written:

 FPGrowth FPMiner = new FPGrowth();
 FPMiner.buildAssociations(dataset);
 AssociationRules rules = FPMiner.getAssociationRules();
 List<AssociationRule> rule = rules.getRules();

This gives me an error as:

Cannot implicitly convert type 'java.util.List' to 'System.Collections.Generic.List'. An explicit conversion exists (are you missing a cast?)

So, I added a cast to the last line as:

List<AssociationRule> rule = (System.Collections.Generic.List<AssociationRule>)rules.getRules();

The error goes away but I get an exception when I run my code, saying:

System.InvalidCastException was unhandled Message=Unable to cast object of type 'java.util.ArrayList' to type System.Collections.Generic.List`1[weka.associations.AssociationRule]'. Source=WindowsFormsApplication1

The stacktrace goes as:

  StackTrace:
       at DetectGroup.Form1.GenerateARFF() in C:\Users\user\Documents\Visual Studio 2010\Projects\DetectGroup\DetectGroup\Form1.cs:line 279
       at DetectGroup.Form1.findNearestNeighbours() in C:\Users\user\Documents\Visual Studio 2010\Projects\DetectGroup\DetectGroup\Form1.cs:line 236
       at DetectGroup.Form1.findSelectedTraj() in C:\Users\user\Documents\Visual Studio 2010\Projects\DetectGroup\DetectGroup\Form1.cs:line 165
       at DetectGroup.Form1.button2_Click(Object sender, EventArgs e) in C:\Users\user\Documents\Visual Studio 2010\Projects\DetectGroup\DetectGroup\Form1.cs:line 404
       at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
       at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
       at System.Windows.Forms.Control.WndProc(Message& m)
       at System.Windows.Forms.ButtonBase.WndProc(Message& m)
       at System.Windows.Forms.Button.WndProc(Message& m)
       at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
       at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       at DetectGroup.Program.Main() in C:\Users\user\Documents\Visual Studio 2010\Projects\DetectGroup\DetectGroup\Program.cs:line 18
       at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()   InnerException:

I am unable to figure out what to do now. I have tried searching stuff but haven't yet got the solution. I understand that the error is because getRules() returns java.util.List while I am trying to use it as System.Collections.Generic.List. What can I do to avoid it? Any help would be great!

Also, is there any data mining library (like Weka) available in C#?

Thank you!

回答1:

I am answering my own question. I used this link to solve the problem I was facing. Thanks @SecretSquirrel(see the comments) and @Jon Iles (see the answer I've linked).

来源：https://stackoverflow.com/questions/18313100/using-weka-in-c-unable-to-cast-object-of-type-java-util-arraylist-to-type-s