How to present credentials in order to open file?

Question

How do I specify the username and password in order for my program to open a file for reading? The program that needs to access the file is running from an account that does

Answer 1

I have used the Nuget package NuGet Gallery | Simple Impersonation Library 1.1.0 but there are others; search on Impersonation for the others.

Example usage using the interactive login to work with file structures:

using (Impersonation.LogonUser("{domain}",
                               "{UserName}", 
                               "{Password}", 
                               LogonType.Interactive))
{
     var directory = @"\\MyCorpServer.net\alpha\cars";

     Assert.IsTrue(Directory.Exists(directory));
}

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James' answer below was before Nuget and before he would later have the most downloaded package on Nuget. Ironic eh?