title: "must declare the scalar variable '@x'" when binding SQL parameters
body: <p>I'm getting error in visual studio error is "must declare the scalar variable '@PhNo', I couldn't guess where I did misspell. I hope that will clear my bug , 
  thanks in advance. :) :)</p>
  
  <p>C# code:</p>
  
  <pre><code>string Name = Session["Username"].ToString();
  con.Open();
  SqlCommand Update_cmd = new SqlCommand("Update RegisterUser set FullName = @Name, PhoneNo = @PhNo ,EmailId = @ID WHERE UserName = '"+Name+"'", con);
  Update_cmd.Parameters.AddWithValue("@Name",txtFullName.Text);
  Update_cmd.Parameters.AddWithValue("@PhNo",txtPhNo.Text);
  Update_cmd.Parameters.AddWithValue("@ID", txtMailID.Text);
  Update_cmd.ExecuteNonQuery();
  lblResultMsg.Text = "Your Profile has been successfully saved";
  con.Close();
  </code></pre>