Problem in Gridview with rowcommand

Question

HI Every one

i have one grid in that i add one button and i set RowCommand event like this
OnRowCommand="gvProject_RowCommand" and the code for button is
<asp:Button ID="btnSendForApproved" runat="server" Text="SendForApproved" CommandName="SendRequest" CommandArgument="<%# ((GridViewRow) Container).RowIndex %>"  />

when i click the button on page its not generating the event please any one tell me where i am doing mistake

thanks in advance