How can I find the users windows login username from ASP.Net?

I have an ASP.Net web application 开发者_运维知识库running on an IIS server, and I need to find the visitors login username.

How can I can find this? When testing locally it found my username using new WindowsPrincipal(WindowsIdentity.GetCurrent());, but it finds NETWORK SERVICE when running the app on the server.

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I assume you use forms authentication. Try:

User.Identity.Name