How to Turn Off Impersonation Just in a Couple Instances

Can I turn off impersonation just in a couple instances

Make sure the Application Pool do have the proper rights that you need.

Then, when you want to revert to the application pool identity... run the following:

private WindowsImpersonationContext context = null;
public void RevertToAppPool()
{
    try
    {
        if (!WindowsIdentity.GetCurrent().IsSystem)
        {
            context = WindowsIdentity.Impersonate(System.IntPtr.Zero);
        }
    }
    catch { }
}
public void UndoImpersonation()
{
    try
    {
        if (context != null)
        {
            context.Undo();
        }
    }
    catch { }
}

Temporary disabling of impersonation in MVC5

So, I was able to solve it.

Thanks to: Can I turn off impersonation just in a couple instances

I used:

using (var impersonationContext = WindowsIdentity.Impersonate(IntPtr.Zero))

Temporarily disable impersonation in ASP

I've got around the impersonation problem in a different way. Just wrote an ASP.net script to save files using HttpPostedFile, based on this one, and it worked like a charm. The files are (probably) being written under the app pool user configured in IIS.

How do I get a .net web service call to stop impersonating to perform a task

It seems that the method I was using is fine. The error was a problem with the sql connection and the assumption that it was Impersonation that was failing. I was confirming my assumption by using the wrong check to verify the identity. The code in my original question does in fact work.

Calling WindowsIdentity.Impersonate does nothing

Giving write access to the App_Data folder for the Users group fixed the issue. Not sure what that has to do with impersonation though.

Storing a password for user impersonation

The safest solution is to actually create a service, which runs under a user with the correct permissions. Your Winforms application would then just use a tight interface to the service to tell it what needs to be done. How feasible this is depends on what exactly you're trying to do.

Trying to do this using just the winforms application is tricky. If a user application can do something, so can the user. Remember, there's no such thing as "application permissions" - only user permissions. The GUI application will run as some user, and that user can do everything the application can.

Read local file as local system, not as current user

You must use some kind of impersonation. You can find options here: https://support.microsoft.com/en-us/help/306158/how-to-implement-impersonation-in-an-asp-net-application

Impersonate the IIS authenticated account or user

Impersonate a specific user for all the requests of an ASP.NET application

Impersonate the authenticating user in code
Impersonate a specific user in code

Example config for all requests

<identity impersonate="true" 
          userName="domain\user"  
          password="password" />

The domain user should have the required access.

If you want to go with the third option, check this answer here which uses the following to impersonate per code block:

try
{
    if (!WindowsIdentity.GetCurrent().IsSystem)
    {
        using (WindowsIdentity.Impersonate(IntPtr.Zero))
        {
          // Do stuff here
        }
    }
}
catch { }