Null Reference Exception
<p>in c sharp 
win-forms</p>

<p>i have added a combo box control to my form
and added items accordingly into the combo box
m trying to the item on select-index is assigned to a string which is passed as parameter to function declared in the following manner:</p>

<pre><code>private void cmbPayment_SelectedIndexChanged(object sender, EventArgs e)
    {
        string pm = cmbLocation.SelectedItem.ToString();
        payment(pm);
    }
</code></pre>

<p>THE FUNCTION:</p>

<pre><code>public void payment(string pym)
    {
        jd.PaymentMode = pym;

    }
</code></pre>

<p><img src="http://img42.imageshack.us/img42/8691/adssd.png" alt="alt text"></p>
