When I insert a WinForm control in Word Document, I get this exception.

Question

Hi All,
Sometimes, when I insert a general Custom WinForm UserControl in Word Document, I receive this exception. It occurred as accidental. I traced this issue. And debug it. It occurred in this code snippet:
var cs = vstoDoc.Controls.AddControl(CustomControl, range, width, height, controlName);
I checked CustomControl,range,width,height,controlName, vstoDoc, vstoDoc.Controls, all of them are not null object. I am confused.
The Exception:
************** Exception Text **************
System.NullReferenceException: Object reference not set to an instance of an object.
   at System.Windows.Forms.Control.ActiveXImpl.InPlaceActivate(Int32 verb)
   at System.Windows.Forms.Control.ActiveXImpl.OnFocus(Boolean focus)
   at System.Windows.Forms.Control.OnGotFocus(EventArgs e)
   at System.Windows.Forms.Control.WmSetFocus(Message& m)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
   at System.Windows.Forms.ContainerControl.WmSetFocus(Message& m)
   at System.Windows.Forms.ContainerControl.WndProc(Message& m)
   at System.Windows.Forms.UserControl.WmSetFocus(Message& m)
   at System.Windows.Forms.UserControl.WndProc(Message& m)
   at Microsoft.VisualStudio.OfficeTools.Controls.VSTOContainerControl.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ActiveXImpl.System.Windows.Forms.IWindowTarget.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
************** Loaded Assemblies **************
mscorlib
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    Win32 Version: 4.0.30319.34209 built by: FX452RTMGDR
    CodeBase: file:///C:/Windows/Microsoft.NET/Framework/v4.0.30319/mscorlib.dll
Microsoft.VisualStudio.Tools.Office.Runtime
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    Win32 Version: 10.0.50903.0
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/Microsoft.VisualStudio.Tools.Office.Runtime/v4.0_10.0.0.0__b03f5f7f11d50a3a/Microsoft.VisualStudio.Tools.Office.Runtime.dll
System.Core
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    Win32 Version: 4.0.30319.34209 built by: FX452RTMGDR
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Core/v4.0_4.0.0.0__b77a5c561934e089/System.Core.dll
System
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    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System/v4.0_4.0.0.0__b77a5c561934e089/System.dll
System.Security
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    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Security/v4.0_4.0.0.0__b03f5f7f11d50a3a/System.Security.dll
System.Xml
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System.Configuration
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Microsoft.VisualStudio.Tools.Applications.Hosting
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Microsoft.VisualStudio.Tools.Applications.Runtime
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    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/Microsoft.VisualStudio.Tools.Applications.Runtime/v4.0_10.0.0.0__b03f5f7f11d50a3a/Microsoft.VisualStudio.Tools.Applications.Runtime.dll
System.Deployment
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Microsoft.VisualStudio.Tools.Applications.ServerDocument
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System.Windows.Forms
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    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Windows.Forms/v4.0_4.0.0.0__b77a5c561934e089/System.Windows.Forms.dll
System.Drawing
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    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Drawing/v4.0_4.0.0.0__b03f5f7f11d50a3a/System.Drawing.dll
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Microsoft.Office.Tools
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Microsoft.Office.Tools.Word
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    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/Microsoft.Office.Tools.Word/v4.0_10.0.0.0__b03f5f7f11d50a3a/Microsoft.Office.Tools.Word.dll
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Microsoft.Office.Tools.Common.v4.0.Utilities
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office
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FRP
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Thanks,

Answer 1

Hi Yang,
Base on my test in Office 2007, it works fine, this is my code below:
internal void AddUserControl()
UserControl1 u = new UserControl1();
var vstoDoc = this.Application.ActiveDocument.GetVstoObject();
vstoDoc.Controls.AddControl(u, this.Application.Selection.Range, 150, 150, "MyUserControl");
Could you reproduce that issue in other machine and new project?
Regards
Starain
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