Dropdownlist SelectedIndexChanged not firing on aspx page

Question

I want to auto click the search button whenever user select a value from drop down list.

code snippet:

Added the event handler in InitializeComponent() :

this.ddltrim.SelectedIndexChanged += new     System.EventHandler(this.ddltrim_SelectedIndexChanged);

code:

private void ddltrim_SelectedIndexChanged(object sender, System.EventArgs e)
            {
        if(ddlStores.Items.Count ==1)
            btnSearch_Click("Search", null);
    }

In designer:

<asp:dropdownlist id=ddltrim width="100%" Runat="server" AutoPostBack="True" EnableViewState="True">    
<asp:ListItem Value="Select Submodel" Selected="True">
      Select SubModel
      </asp:ListItem></asp:dropdownlist>

But selectIndexChanged in not firing when i select any value from ddl. Have to manually click the button search.

Answer 1

Try

<asp:dropdownlist id=ddltrim width="100%" Runat="server" AutoPostBack="True" EnableViewState="True" onselectedindexchanged="ddltrim_SelectedIndexChanged">
<asp:ListItem Value="Select Submodel" Selected="True">Select SubModel</asp:ListItem>

Answer 2

Try to set your add event code in Page_PreInit method

protected void Page_PreInit(object sender, EventArgs e)
{
    this.ddltrim.SelectedIndexChanged += new System.EventHandler(this.ddltrim_SelectedIndexChanged);
}