One managed way to insert JS into the page while in the back-end C# code is using
RegisterClientScriptBlock
, see example:
ClientScriptManager cs = Page.ClientScript;
String csname1 = "PopupScript";
String csname2 = "ButtonClickScript";
StringBuilder sb = new StringBuilder();
cstext2.Append("<script type=\"text/javascript\"> function DoClick() {");
sb.Append("Form1.Message.value='Text from client script.'} </");
sb.Append("script>");
cs.RegisterClientScriptBlock(cstype, csname2, sb.ToString(), false);
best,
H