Check UserID exists in Active Directory using C#

How can we check whether the USERID exists in Active Directory or not.

I have LDAP String and UserID, can I find whether that UserID exist开发者_开发百科s in Active Directory or not. I am using this for ASP.NET Web Application (.NET 3.5)

You can do something along the lines of (replacing domain with the domain you're authenticating against or removing the parameter altogether):

public bool DoesUserExist(string userName)
{
    using (var domainContext = new PrincipalContext(ContextType.Domain, "DOMAIN"))
    {
        using (var foundUser = UserPrincipal.FindByIdentity(domainContext, IdentityType.SamAccountName, userName))
        {
            return foundUser != null;
        }
    }
}

To achieve checking for if a user exists. This comes from the System.DirectoryServices.AccountManagement namespace and assembly.

You can find more information at http://msdn.microsoft.com/en-us/library/system.directoryservices.accountmanagement.aspx

You may want to check more into PrincipalContext as it has interesting methods for authenticating user credentials and such.

I would use the System.DirectoryServices.AccountManagement namespace.

string UserID = "grhm";
bool userExists = false;

using (var ctx = new PrincipalContext(ContextType.Domain))
{
    using (var user = UserPrincipal.FindByIdentity(ctx, UserID))
    {
        if (user != null)
        {
            userExists = true;
            user.Dispose();
        }
    }
}

See http://msdn.microsoft.com/en-us/library/bb344891.aspx for more info