Running Javascript after control's selected value has been set
<p>Simple asp.net application.</p>

<p>I have two drop-down controls, on the first-drop down I have a javascript <code>onChange</code> event. The javascript enables the second drop-down and removes a value from it (the value selected in the first drop-down). If they click the blank first value of the drop-down, then the second drop-down will be disabled (and the options reset).</p>

<p>I also have code in the <code>OnPreRender</code> method that will enable or disable the second drop-down based on the value of the first drop-down. This is so that the value of the first drop-down can be selected in code (loading user settings).</p>

<p>My problem is:</p>

<ol>
<li>The user selects something in the first drop-down. The second drop-down will become enabled through javascript. </li>
<li>They then change a third drop-down that initiates a post back. After the post back the drop-downs are in the correct state (first value selected, second drop-down enabled).</li>
<li>If they then click the back button, the second drop-down will no longer be enabled although it should be since there's something selected in the first drop-down.</li>
</ol>

<p>I've tried adding a startup script (that will set the correct state of the second-drop down) through <code>ClientScript.RegisterStartupScript</code>, however when this gets called the first drop-down has a <code>selectedIndex</code> of <code>0</code>, not what it actually is. My guess is that the value of the selection gets set after my start script (but still doesn't call the <code>onChange</code> script).</p>

<p>Any ideas on what to try?</p>
