Enable disable show hide controls in grdview edit mode RowEditing or PreRender method

In many asp.net (C# VB.Net) forum i found that developers ask how to enable or disable or show or hide asp.net server side controls like textbox,label,checkbox,checkboxlist,radiobutton,radiobuttonlist & dropdownlist or combo box in gridview edit mode. Everyone tries to find those controls within RowEditing event handler but they didn't get the control by using findcontrol method and editindex