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ASP.NET 1.0 and 1.1 Basics ASP.NET discussion for users new to coding in ASP.NET 1.0 or 1.1. NOT for the older "classic" ASP 3 or the newer ASP.NET 2.0.
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Old February 13th, 2006, 02:54 AM
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Default How to cast ASP Drop Down List to HtmlSelect?

I have an <asp:Drop Down List/> that is dynamically populated by Javascript depending on what the previous Drop Down List selection is. However, on "Search" button click, I want the server to take the Selected Value from <asp:Drop Down List/> and pass it to a parameter.
The problem is, when I step through the code in Javascript, the DDL has the property of Form1.ddl.option.value and Form1.ddl.option.text. When I step through the same ddl in Code behind, there is no value for DataTextField and DataValueField.

I was trying to cast the ASP DDL to HtmlSelect, because the Javascript populates the ddl as HtmlSelect. This is an invalid cast and VS.NET 2003 won't let me.

So what can I do???

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Old February 13th, 2006, 12:56 PM
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You can't cast it. You could also use <select runat="server">, which would be the HtmlSelect control instead. When rendered, the asp:DropDownList is a <select> element, so I dont' now what the problem is...

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Old February 13th, 2006, 12:57 PM
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Oh, and DataTextField and DataValueField are for databinding; the selectedvalue is for the selected value or selecteditem.text for the text, in the code-behind.

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Old February 13th, 2006, 11:04 PM
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There will be an inherent problem if you change the <select> elements contents for a server control. The server control will restore the contents of the option list from viewstate and then apply whatever change was posted. So if you start with the options 1, 2 & 3, then change those options in javascript to 4, 5 & 6, the server side code will ignore the client side change in the list and restore the control with 1, 2 & 3. It will also attempt to apply the change (now you'll have either 4, 5 or 6 selected) but it can't find them in the current list so it will default back to the first option (1). This can cause erroneous index change events or other strange things to happen. If you want to be able to support this client-side option list change behavior, you'll have to use standard non-server form elements and manually capture the post values using the Request.Form collection. This is doing it old school style but it could be done.


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