c# Export plugin crashing Max

[Anonymous]

using System;
using System.Collections.Generic;
using Autodesk.Max;
using Autodesk.Max.Plugins;

namespace MaxDotNet
{

public static class PluginMain
 {
 public static void AssemblyMain()
 {
 Autodesk.Max.GlobalInterface.Instance.COREInterface.AddClass(new DotNetSimpleExportDesc());
 }

 public static void AssemblyShutdown()
 {
 }

 }
    
class DotNetSimpleExportDesc : ClassDesc2
{
IClass_ID _classid;
public DotNetSimpleExportDesc()
{
  _classid = GlobalInterface.Instance.Class_ID.Create(0x4a7dd792, 0x68f24659);
}


 public override string ClassName{get {return "DotNetSimpleExport";}}

 public override string Category { get { return "DotNetSimpleExport"; } }

 public override IClass_ID ClassID
 {
 get
 {
 return _classid;
 }
 }

 public override SClass_ID SuperClassID
 {
 get { return  SClass_ID.SceneExport; }
 }

 public override object Create(bool loading)
 {
            return new DotNetSimpleExport();
 }
 
 public override bool IsPublic
 {
 get { return true; }
 }
 }
    
 public class DotNetSimpleExport : SceneExport
 {
 
 public DotNetSimpleExport()
 {
 }
 
 public override int ExtCount
 {
 get
 {
 return 1;
 }
 }
 
 public override string Ext(int index)
 {
 return ".txt";
 }
 
 public override string LongDesc 
 {
 get { return "ExporterByMaxDotNetSDK";}
 }
 
 public override string ShortDesc
 {
 get {return "SimpleExport";}
 }
 
 public override string AuthorName 
 {
 get {return "SITT";}
 }
 
 public override string CopyrightMessage 
 {
 get {return "Copyright ©2013 SITT";}
 }
 
 public override string OtherMessage1()
 {
 return "Nothing";
 }
 
 public override string OtherMessage2()
 {
 return "NothingToo";
 }
 
 public override uint Version 
 {
 get {return 100;}
 }
 
 public override void ShowAbout(IntPtr hWnd)
 {
 }
 
 public override bool SupportsOptions(int ext, uint options)
 {
 return base.SupportsOptions(ext, options);
 }
 
 public override int DoExport(string name, IExpInterface ei, IInterface i, bool suppressPrompts, uint options)
 {
 System.Windows.Forms.MessageBox.Show(name);
 return 1;
 }
 }
}

thank you

[Anonymous]

same probleme here, don't know why...