Load an dll failed while debugging

Hi all,

These days I meet a problem trouble me much time. When I debug a .net WPF project slowly with Visual studio 2010, my code will throw out some exception like this, and the bebugging will be end by un-catched excpetion, from the innerexcpetion, I can get it information that can't load abt.Controls.SciChart.Wpf.2.3& or it's depency

A first chance exception of type 'System.Xml.XmlException' occurred in System.Xml.dll
A first chance exception of type 'System.Xml.XmlException' occurred in System.Xml.dll
A first chance exception of type 'System.IO.FileNotFoundException' occurred in mscorlib.dll
A first chance exception of type 'System.NullReferenceException' occurred in Microsoft.VisualStudio.DebuggerVisualizers.dll
A first chance exception of type 'System.NullReferenceException' occurred in Microsoft.VisualStudio.DebuggerVisualizers.dll
A first chance exception of type 'System.IO.FileNotFoundException' occurred in mscorlib.dll
'Main.vshost.exe' (Managed (v4.0.30319)): Loaded 'p3kurvhc'
A first chance exception of type 'System.NullReferenceException' occurred in Microsoft.VisualStudio.DebuggerVisualizers.dll
A first chance exception of type 'System.NullReferenceException' occurred in Microsoft.VisualStudio.DebuggerVisualizers.dll
'Main.vshost.exe' (Managed (v4.0.30319)): Loaded 'Abt.Controls.SciChart.Wpf.2.3&'
A first chance exception of type 'System.IO.FileNotFoundException' occurred in mscorlib.dll
A first chance exception of type 'System.TypeInitializationException' occurred in Abt.Controls.SciChart.Wpf.2.3.dll

But same code, just debug quickly than before, there will be not such exception and bebugging goes well. I am want to know about these questions:

1. from the output I know the app already load "abt.controls.scichart.wpf.2.3.dll" at first, why we still load it "abt.controls.sichart.wpf.2.3.dll &" later.

2. what is DebuggerVisualizers? why does it throw the null-reference exception?

3. what is 'p3kurvhc'? "abt.controls.scichart.wpf.2.3.dll" is encrypted.

4. why sometimes the debugging can goes well, but sometimes not?

Thanks.

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FM