This tutorial for asp.net programmers will show you how to run JavaScript from code behind follow the next steps:
1. Set the Body tag in your page/master page:
<body runat="server" id="MyBody">
2. Write the script tag in your page:
<script src="MyFunction.js" type="text/javascript"></script>
3. In the code behind attach the onload attribute to the body tag:
protected void Page_Load(object sender, EventArgs e)
{
MasterPageBodyTag = (HtmlGenericControl)Page.Master.FindControl(“MyBody”);
MasterPageBodyTag.Attributes.Add(“Onload”, “MyFunction()”);
}