WinForms: Why do I get InvalidCastException when showing folder browser dialog?
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by Marek
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Published on 2010-05-11T15:04:09Z
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2010/05/11
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I am randomly getting InvalidCastException when showing FolderBrowserDialog and also many clients have reported this.
I have not been able to find anything relevant on the internet. Does anyone know what causes this/how to fix this?
My code:
using (FolderBrowserDialog fbd = new FolderBrowserDialog())
{
fbd.ShowNewFolderButton = false;
if (fbd.ShowDialog() == DialogResult.OK)
Stack trace:
Error: System.InvalidCastException:
'Unable to cast object of type 'System.__ComObject' to type 'IMalloc'.'.
Stack trace:
at System.Windows.Forms.UnsafeNativeMethods.Shell32.SHGetMalloc(IMalloc[] ppMalloc)
at System.Windows.Forms.FolderBrowserDialog.GetSHMalloc()
at System.Windows.Forms.FolderBrowserDialog.RunDialog(IntPtr hWndOwner)
at System.Windows.Forms.CommonDialog.ShowDialog(IWin32Window owner)
at System.Windows.Forms.CommonDialog.ShowDialog()
EDIT: Additional information: I have been able to reproduce this only when running in VS2008 debugger.
When running out of debugger, it happens only very rarely (happened once or twice in 6 months) on my 64 bit Windows 7 and goes away after restart.
The clients are certainly not running the app in debugger so it is surely reproducible out of debugger.
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