Update: There is an existing .Net Framework method Page.GetPostBackEventReference that emits client-side script that initiates postback and also provides a reference to the control that initiated the postback event. It is well described in MSDN article “Generating Client-Side Script for Postback“. So my function should call and in most cases GetPostBackEventReference can be used directly**.**
Original Post:
I've used a function to submit postback from my javascript by passing Id of the link server control as it was suggested in article “How postback works in ASP.NET”
//call the postback function with the right ID
__doPostBack('ControlId','');
and it worked fine for a while.
However when I moved the link to the User control, it stopped to work.
I recognized that I need to provide fully qualified Control.ClientId but it didn't work.
In debugger I found that when calling the __doPostBack(), ASP.NET generates ID with dollar - $ -separator, not underscore that is used in ClientID, e.g. 'userContol1$linkContol1'.
I found confirmation to this in ASP.NET Server Control - Design Time Support and .NET Development: PressButton Design and Server Control . Microsoft provides UniqueIDWithDollars internal method, that can be accessed through reflection.
However I found that it is simpler just to duplicate code in static function.
The working version of javascript function to __doPostBack :
public static bool RegisterFunctionToPostBack(string sFunctionName,Control ctrl)
{ //from http://www.xefteri.com/articles/show.cfm?id=18 How postback works in ASP.NET
if (HttpContext.Current.Request.Browser.JavaScript)
{
string sJS =" function " + sFunctionName + @"()
{
//call the postback function with the right ID
__doPostBack('" + UniqueIDWithDollars(ctrl) + @"','');
}";
sJS=JScriptHelper.JScript(sJS);
ctrl.Page.RegisterStartupScript(sFunctionName, sJS);
return true;
}
return false;
}
//from http://www.codeproject.com/aspnet/DesignTimeSupport.asp
public static string UniqueIDWithDollars(Control ctrl)
{
string sId = ctrl.UniqueID;
if (sId == null)
{
return null;
}
if (sId.IndexOf(':') >= 0)
{
return sId.Replace(':', '$');
}
return sId;
}
If I would start the function from the scratch, I probably would consider ScriptCallback/AJAX approach.
ctrl.Page.GetPostBackEventReference(ctrl) instead of
__doPostBack('" + UniqueIDWithDollars(ctrl) + @"','');