Question

I am calling a javascript on index change of a DropDownList, i do as follows

<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" 
OnSelectedIndexChanged="toggleVisibility('Button1');">

I get the error during compiling as for the above line of code

Too many characters in character literal

Can anyone help me solve this issue?

Answer 1

OnSelectedIndexChanged is a server side event, you need to set OnClientClick instead and set AutoPostBack=”false” if your intention is to toggle visibility on client side

For the server side

<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" 
OnSelectedIndexChanged="toggleVisibility">

protected object toggleVisibility(object sender, EventArgs e)
{
   Button1.Visible = !Button1.Visible;
}

So for the events you need to use the method name which has a specific signature, defined by the event type. Here is object sender, EventArgs e

Edit

DropDownList has no property called OnClientClick, so you need to add it in codebehind

DropDownList1.Attributes.Add("onchange","toggleVisibility('Button1');");