CODEWITHSUNDEEP
c#asp.net
Simon Keep
Simon Keep

Reputation: 10002

How to Identify Postback event in Page_Load

We have some legacy code that needs to identify in the Page_Load which event caused the postback. At the moment this is implemented by checking the Request data like this...

if (Request.Form["__EVENTTARGET"] != null
&& (Request.Form["__EVENTTARGET"].IndexOf("BaseGrid") > -1 // BaseGrid event ( e.g. sort)
       || Request.Form["btnSave"] != null // Save button

This is pretty ugly and breaks if someone renames a control. Is there a better way of doing this?

Rewriting each page so that it does not need to check this in Page_Load is not an option at the moment.

Upvotes: 5

Views: 8091

Answers (3)

AProgrammer
AProgrammer

Reputation: 158

I am just posting the entire code (which includes the image button / additional control check that causes postback). Thanks Espo.

public Control GetPostBackControl(Page page)
{ 
   Control control = null; 
   string ctrlname = page.Request.Params.Get("__EVENTTARGET"); 
   if ((ctrlname != null) & ctrlname != string.Empty)
      { 
         control = page.FindControl(ctrlname); 
       }
  else 
      {
        foreach (string ctl in page.Request.Form) 
           { 
              Control c = page.FindControl(ctl); 
              if (c is System.Web.UI.WebControls.Button) 
                  { control = c; break; }
           }
       }
// handle the ImageButton postbacks 
if (control == null) 
{ for (int i = 0; i < page.Request.Form.Count; i++) 
    { 
        if ((page.Request.Form.Keys[i].EndsWith(".x")) || (page.Request.Form.Keys[i].EndsWith(".y"))) 
             { control = page.FindControl(page.Request.Form.Keys[i].Substring(0, page.Request.Form.Keys[i].Length - 2)); break; 
             }
     }
 } 
return control; 
}

Upvotes: 0

AProgrammer
AProgrammer

Reputation: 158

In addition to the above code, if control is of type ImageButton then add the below code,

if (control == null) 
{ for (int i = 0; i < page.Request.Form.Count; i++) 
    { 
        if ((page.Request.Form.Keys[i].EndsWith(".x")) || (page.Request.Form.Keys[i].EndsWith(".y"))) 
             { control = page.FindControl(page.Request.Form.Keys[i].Substring(0, page.Request.Form.Keys[i].Length - 2)); break; 
             }
     }
 }

Upvotes: 0

Espo
Espo

Reputation: 41929

This should get you the control that caused the postback:

public static Control GetPostBackControl(Page page)
{
    Control control = null;

    string ctrlname = page.Request.Params.Get("__EVENTTARGET");
    if (ctrlname != null && ctrlname != string.Empty)
    {
        control = page.FindControl(ctrlname);
    }
    else
    {
        foreach (string ctl in page.Request.Form)
        {
            Control c = page.FindControl(ctl);
            if (c is System.Web.UI.WebControls.Button)
            {
                control = c;
                break;
            }
        }
    }
    return control;
}

Read more about this on this page: http://ryanfarley.com/blog/archive/2005/03/11/1886.aspx

Upvotes: 7

Related Questions