How to get current user who's accessing an ASP.NET application?

The quick answer is User = System.Web.HttpContext.Current.User

Ensure your web.config has the following authentication element.

<configuration>
    <system.web>
        <authentication mode="Windows" />
        <authorization>
            <deny users="?"/>
        </authorization>
    </system.web>
</configuration>

Further Reading: Recipe: Enabling Windows Authentication within an Intranet ASP.NET Web application

Using System.Web.HttpContext.Current.User.Identity.Name should work. Please check the IIS Site settings on the server that is hosting your site by doing the following:

1. Go to IIS → Sites → Your Site → Authentication

   

2. Now check that Anonymous Access is Disabled & Windows Authentication is Enabled.

   

3. Now System.Web.HttpContext.Current.User.Identity.Name should return something like this:

   domain\username

If you're using membership you can do: Membership.GetUser()

Your code is returning the Windows account which is assigned with ASP.NET.

Additional Info Edit: You will want to include System.Web.Security

using System.Web.Security