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Editorial Team
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Asked: 2026-06-12T10:17:48+00:00

I have a variable in a code behind control. I want to pass this

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I have a variable in a code behind control. I want to pass this value to an Ext.Net control in the web control. In my instance I have an ext.multicombo, and I want to pass a value to it’s Tooltip.

Code Behind:

protected override void OnPreRender(EventArgs e)
{
this.MaxFuelFilter = System.Configuration.ConfigurationManager.AppSettings["MyVariable"]; 
}

Control.aspx

<ext:multicombo ID="ddlFlightNumber" runat="server" ClientID="ddlFlightNumber" IndicatorTip="blah blah blah  <%=MyVariable%> blah blah blah"></ext:multicombo>

How do I do something like this?

Thanks

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1 Answer

  1. Editorial Team

    There are a few issues:

    The syntax you’re using will not work with ASP.NET Controls. This is an ASP.NET limitation, and not related to Ext.NET.

    This is not valid ASP.NET syntax:

    PropertyName="foo foo <%=MyVariable%>"

    And, this is not valid ASP.NET syntax:

    PropertyName="<%=MyVariable%>"

    To pass a value into the property, you’ll need to use the <%# %> DataBinding syntax.

    Although, this is also not valid ASP.NET syntax:

    PropertyName="foo foo <%# MyVariable %>"

    The property must ONLY contain the databind variable/script, example

    PropertyName="<%# MyVariable%>"

    AND… you must call .DataBind() on the Control, example

    this.MyControl1.DataBind();

    OR, with Ext.NET Controls, you can set the .AutoDataBind="true" property and DataBinding will be automatically handled for you, example

    <ext:TextField runat="server" PropertyName="<%# MyVariable%>" AutoDataBind="true" />

    The above custom property is auto-serialized into JavaScript and is now available to the client-side instance of that control (and others). You can then call that property from other JavaScript code.

    For your scenario, I’d recommend tapping into an <AfterRender> Listener of the <ext:MultiCombo> to get the property value and set something else. The following sample demonstrates the complete scenario (myVar), and also demonstrates another basic technique (myVar2) for passing a JavaScript variable into the client-side from the server-side.

    Example

    <%@ Page Language="C#" %>

<%@ Register assembly="Ext.Net" namespace="Ext.Net" tagprefix="ext" %>

<script runat="server">
    string myVar;
    string myVar2;

    protected void Page_Load(object sender, EventArgs e)
    {
        myVar = "Label 1";
        myVar2 = "Label 2";
    }
</script>

<!DOCTYPE html>

<html>
<head runat="server">
    <title>Ext.NET Example</title>
</head>
<body>
    <form runat="server">
        <ext:ResourceManager runat="server" />

        <ext:TextField 
            ID="TextField1" 
            runat="server" 
            MyVar="<%# myVar %>"
            AutoDataBind="true" 
            FieldLabel="Testing">
            <Listeners>
                <AfterRender Handler="this.setFieldLabel(this.myVar);" />
            </Listeners>
        </ext:TextField>

        <ext:TextField 
            ID="TextField2" 
            runat="server" 
            MyVar="<%# myVar2 %>"
            AutoDataBind="true" 
            FieldLabel="Testing">
            <Listeners>
                <AfterRender Handler="this.setFieldLabel(myVar2);" />
            </Listeners>
        </ext:TextField>

        <script type="text/javascript">
            var myVar2 = "<%= myVar2 %>";
        </script>
    </form>
</body>
</html>

    You should be able to adapt the above to work with your custom Control.

    Hope this helps.

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