I have buttonfield in GridView. How can I access ButtonField in GridView1_RowDataBound. I need to hide this button on basis of a field in the table.

   <asp:buttonfield buttontype="Image" commandname="OK" headertext="Click to OK"
                       ImageUrl="images\green_button.gif" />

   string errorFlag = (DataBinder.Eval(e.Row.DataItem, "error_flag")).ToString() ;
                
               if ( errorFlag == "X" )  {
                     Button bt = (Button)e.Row.FindControl("OK") ;
             
                     bt.Visible = false;  }

It doesn;t work.

i have just learned this from Ed.

http://forums.asp.net/t/1258625.aspx

find control searches for the control by ID, you did not specify an ID for your button field. <asp:buttonField id="btnfield1"...

 Gave me error

'System.Web.UI.WebControls.ButtonField' does not have a public property named 'id'.

 Give the buttonfield a id

Because you are finding control by CommandName you are not able to do so, You need to find control by its ID.
<asp:buttonfield buttontype="Image" ID="buttonName" headertext="Click to OK"
                       ImageUrl="images\green_button.gif" /> 

   string errorFlag = (DataBinder.Eval(e.Row.DataItem, "error_flag")).ToString() ;                 
               if ( errorFlag == "X" )  {
                    Button bt = ctype(e.Row.FindControl("buttonName") , Button)
                     bt.Visible = false;  }

Hope this helps.

 Thankyou all for helping me.

But ButtonField does not have "id" .

I get this error -  

Type 'System.Web.UI.WebControls.ButtonField' does not have a public property named 'id'.

convert buttonfield to templatefield.  the link I sent you should help

hmm apparently id is not a buttonfield property. You are supposed to reference them by index accoring to msdn 

To determine the index of the record that raises the command event, use the CommandArgument property of the event argument that is passed to the command event for the data-bound control. The ButtonField class automatically populates the CommandArgument property with the appropriate index value. (http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.buttonfield.aspx)

Another option is to just wrap the buttonfield in a panel and hide the panel when you want, this will hide the button with it 

<asp:Panel id="pnlButtonHide" runat="server>
    <asp:ButtonField>
</asp:Panel>

//When you want to hide
((Panel)whereyourpanelis.findControl("pnlButtonHide")).Visible = fasle;