在 Asp.Net MVC 5 中获取登录用户的 UserID [英] Get UserID of logged-in user in Asp.Net MVC 5

问题描述

I'm relatively new to ASP.Net MVC and try to use the built-in user login functionality now. I'm able to register an user in the registration view. If I try to login with the created user this also works. I'm redirected to the master page.

But I'm not able to get the UserID of the current user. I tried my code in the HomeController and in the AccountController, but both didn't work. The statement in the first line returns always null.

var userID = User.Identity.GetUserId();

if (!string.IsNullOrEmpty(userID))
{
    var manager = new UserManager<ApplicationUser>(new UserStore<ApplicationUser>(ApplicationDbContext.Create()));
    var currentUser = manager.FindById(User.Identity.GetUserId());
}

Do I have to to something else before getting the UserID?

解决方案

The answer is right there in your code. What does this return?

var userID = User.Identity.GetUserId();

If you are using ASP.NET Identity, then after logging in (and redirecting to another page), the IPrincipal.IIdentity should be a ClaimsIdentity. You can try this:

var claimsIdentity = User.Identity as ClaimsIdentity;
if (claimsIdentity != null)
{
    // the principal identity is a claims identity.
    // now we need to find the NameIdentifier claim
    var userIdClaim = claimsIdentity.Claims
        .FirstOrDefault(x => x.Type == ClaimTypes.NameIdentifier);

    if (userIdClaim != null)
    {
        var userIdValue = userIdClaim.Value;
    }
}

The above block of code is not exactly, but essentially, what the IIdentity.GetUserId extension method does.

If none of this works, then the user may not really be logged into your site yet. After logging in, you have to redirect to another page before the server will write the authentication cookie to the browser. This cookie must be written before the User.Identity has all of this claims information (including the NameIdentifier) on subsequent requests.

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