__EVENTTARGET is empty on postback of button click

I have a button on aspx page

<asp:Button runat="server" CssClass="sc-ButtonHeightWidth" ID="btnFirstSave" Text="Save" OnClick="btnSave_Click" />

I am trying to get the event target and event source in code behind to do some validation based on it. I tried with below code.
string ctrlname = page.Request.Params.Get("__EVENTTARGET");
string ctrlname = Request.Form["__EVENTTARGET"];
string ctrlname = Request.Params["__EVENTTARGET"];

But all the above are giving me empty values. How to get the control which caused postback everytime. Am i doing anyting wrong above?

FYI : I already tried the solution mentioned in this LINK. But its only returning button text for me. I want the buttonID.

Answers:

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Method 1

Asp button renders as input with type submit this method will not fill_EVENTTARGET
controls using "__doPostBack" method to cause postback will add values to _EVENTTARGET
so your button id is missing from _EVENTTARGET you can iterate through all the controls in page to check which control caused postback.

Try this to capture Your control –Here

private string getPostBackControlName()
        {
            Control control = null;
            //first we will check the "__EVENTTARGET" because if post back made by       the controls
            //which used "_doPostBack" function also available in Request.Form collection.
            string ctrlname = Page.Request.Params["__EVENTTARGET"];
            if (ctrlname != null && ctrlname != String.Empty)
            {
                control = Page.FindControl(ctrlname);
            }
            // if __EVENTTARGET is null, the control is a button type and we need to
            // iterate over the form collection to find it
            else
            {
                string ctrlStr = String.Empty;
                Control c = null;
                foreach (string ctl in Page.Request.Form)
                {
                    //handle ImageButton they having an additional "quasi-property" in their Id which identifies
                    //mouse x and y coordinates
                    if (ctl.EndsWith(".x") || ctl.EndsWith(".y"))
                    {
                        ctrlStr = ctl.Substring(0, ctl.Length - 2);
                        c = Page.FindControl(ctrlStr);
                    }
                    else
                    {
                        c = Page.FindControl(ctl);
                    }
                    if (c is System.Web.UI.WebControls.Button ||
                             c is System.Web.UI.WebControls.ImageButton)
                    {
                        control = c;
                        break;
                    }
                }
            }
            return control.ID;

        }

Method 2

I have set usesubmitbehavior to false as of now. A good solution given by Damith above in the comment. As of now its working fine for me without any problem. To know about the property Read this LINK

Hope this will help someone.

Method 3

Just add UseSubmitBehavior=”False” to your button.

<asp:Button runat="server" CssClass="sc-ButtonHeightWidth" ID="btnFirstSave" Text="Save" OnClick="btnSave_Click" UseSubmitBehavior="False" />

Method 4

/// <summary>
/// Gets the ID of the post back control.
/// 
/// See: http://geekswithblogs.net/mahesh/archive/2006/06/27/83264.aspx
/// </summary>
/// <param name = "page">The page.</param>
/// <returns></returns>
public static string GetPostBackControlId(this Page page)
{
    if (!page.IsPostBack)
        return string.Empty;

    Control control = null;
    // first we will check the "__EVENTTARGET" because if post back made by the controls
    // which used "_doPostBack" function also available in Request.Form collection.
    string controlName = page.Request.Params["__EVENTTARGET"];
    if (!String.IsNullOrEmpty(controlName))
    {
        control = page.FindControl(controlName);
    }
    else
    {
        // if __EVENTTARGET is null, the control is a button type and we need to
        // iterate over the form collection to find it

        // ReSharper disable TooWideLocalVariableScope
        string controlId;
        Control foundControl;
        // ReSharper restore TooWideLocalVariableScope

        foreach (string ctl in page.Request.Form)
        {
            // handle ImageButton they having an additional "quasi-property" 
            // in their Id which identifies mouse x and y coordinates
            if (ctl.EndsWith(".x") || ctl.EndsWith(".y"))
            {
                controlId = ctl.Substring(0, ctl.Length - 2);
                foundControl = page.FindControl(controlId);
            }
            else
            {
                foundControl = page.FindControl(ctl);
            }

            if (!(foundControl is Button || foundControl is ImageButton)) continue;

            control = foundControl;
            break;
        }
    }

    return control == null ? String.Empty : control.ID;
}

Source

Method 5

My solution.I add OnClick event like this on my client side

function btnClickSuper(s, e)
{
__doPostBack(s.name, '');
}

here s is object presented my button in DevExpress, where property name contains, as part of, an Id of elment. so ,on server side, I can get Id of button sent postback. Price is server OnClick enevnt isn’t fired.


All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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