I have the following textbox server control in my web page:

<asp:TextBox ID=txtZip runat=server onchange=ZipCode_OnChange(this, <%= txtZip.ClientId %>, txtCity, txtState);/>

When the page renders, it is built including the following:

<input name=txtZip type=text id=txtZip onchange=ZipCode_OnChange(this, &lt;%= txtZip.ClientId %>, txtCity, txtState); />

I'm trying to pass the text box's client IDas the 2nd param to this Javascript function:

function ZipCode_OnChange(txtZipCode, ClientId) {

    var ret;

    ret = WebService.GetCityAndState(txtZipCode.value, OnComplete1, OnError, ClientId);

}

How do I get it to, on the server, evaluate the texbox's control and to pass that literal string to the Javascript function?