[RESOLVED] error assigning value

[VBKNIGHT]

I'm new to C# please help..got error assigning textbox value on my variable usr.

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

public partial class _Default : System.Web.UI.Page 
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (Page.IsPostBack) {
            string usr = username.Text.ToString; -> error on this line
             if (usr == "test")
             {
                 Response.Redirect("userform.aspx");
             }
             else
             { custerrormsg.Text = "Invalid username or password"; }
        }else{

            }
        

    }
}

TIA