Open excel interop with impersonation in C#

Question

Is it possible to open excel interop in C# with impersonation. I want to open excel application to run under different account other than the one which C# program runs in. By default, it opens under same user account that runs C# program.

        MyApp = new Excel.Application();
        MyApp.Visible = false;
        MyApp.DisplayAlerts = false;
        MyBook = MyApp.Workbooks.Open(@"C:\Sample.xlsx");

Any other way to do this also welcomed.

Answer 1

In order to obtain an impersonation context from code behind you can use some unmanaged functions from advapi32.dll .

• Call LogonUser in order to obtain a user token
• Create a WindowsIdentity based on the user token
• Call Impersonate on the windows identity. This will return an WindowsImpersonationContext that can be used later to Undo impersonation
• Call your code here.
• Undo the impersonation ( ctx.Undo(); ) and release resources.

What a mess, don't you think?

Fortunately you don't have to reinvent the wheel again. Uwe Keim wrote a class that does all the above steps under the hood while maintaining reusability.

A small C# class for impersonating a user

using ( new Impersonator( "username", "domainName", "password" ) )
{
   /* code that executes under the new context */
}