c# why wont this display to label
<p>I want to be able to display balance to label and my code is not working. This is code I got so far:</p>

<pre><code>SqlDataReader readdata;

{
    sqlCommandbalance.Connection.Open();
    sqlCommandbalance.Parameters["@accountID"].Value = show.accoundID;
    readdata = sqlCommandbalance.ExecuteReader();
    string balanceDB = null;
    while (readdata.Read())
    {
        balanceDB = readdata["balance"].ToString();
    }
    sqlCommandbalance.Connection.Close();
    balanceShow.Text += " " + balanceDB.ToString();
}
</code></pre>

<p>On this line - <code>balanceShow.Text += " " + balanceDB.ToString();</code> got a error saying Object reference not set to an instance of an object.</p>
