how to use Username or Email id to login in asp.net ?

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C#

ASP.NET

I want user to login by any of the one, either username or Email id. I already have the code for login through username but i want it to be as either username or email address. what changes to make in below code ??

protected void Button1_Click(object sender, EventArgs e)
       {
           SqlConnection con = new SqlConnection("Data Source=jayraj-pc\\sqlexpress;Initial Catalog=Internship;Integrated Security=True;Pooling=False");

           con.Open();
           SqlCommand cmd = new SqlCommand("select * from Users where Username=@username and Password=@password", con);
           cmd.Parameters.AddWithValue("@username", uname.Text);
           cmd.Parameters.AddWithValue("@password", pwd.Text);
           SqlDataAdapter da = new SqlDataAdapter(cmd);
           DataTable dt = new DataTable();
           da.Fill(dt);
           if (dt.Rows.Count > 0)
           {
               Session["UserID"] = dt.Rows[0]["UserID"].ToString();
               Session["FirstName"] = dt.Rows[0]["FirstName"].ToString();
               Session["Username"] = uname.Text;
               Response.Redirect("StudentDashboard.aspx");
           }
           else
           {
               ClientScript.RegisterStartupScript(Page.GetType(), "validation", "<script language='javascript'>alert('Invalid Username and Password')</script>");
           }
       }