I can't update my database through textbox
<p>I can't update my database through textbox. In the database <code>prt</code> is declared as a char datatype. It didn't show any error message.</p>

<p>My coding is...</p>

<pre><code>SqlCommand cmdup= new SqlCommand("UPDATE [port1] SET [prt1]=@prt1 WHERE [no]= 1",cn);
cmdup.Parameters.Add("@prt1", TextBox1.Text); 
cmdup.ExecuteNonQuery(); 
</code></pre>
