Evento RowCommand - como utilizar?

<asp:GridView ID="GridView3" runat="server" OnSelectedIndexChanged="GridView3_SelectedIndexChanged" AutoGenerateColumns="False" OnRowCommand="GridView3_RowCommand">
            <Columns>
                <asp:BoundField DataField="ramal" HeaderText="Ramal" />
                <asp:BoundField DataField="nome" HeaderText="Nome" />
            </Columns>
        </asp:GridView>

Server Error in '/' Application.

Compilation Error

Description: An error occurred during the compilation of a resource required to service this request. Please review the following specific error details and modify your source code appropriately. 

Compiler Error Message: CS1061: 'ASP.rowcommand_aspx' does not contain a definition for 'GridView3_RowCommand' and no extension method 'GridView3_RowCommand' accepting a first argument of type 'ASP.rowcommand_aspx' could be found (are you missing a using directive or an assembly reference?)

Source Error:


Line 119:        <%-- grid lista ramais Teste rowcommand --%>
Line 120:        lista ramais - teste row command <p></p>
Line 121:        <asp:GridView ID="GridView3" runat="server" OnSelectedIndexChanged="GridView3_SelectedIndexChanged" AutoGenerateColumns="False" OnRowCommand="GridView3_RowCommand">
Line 122:            <Columns>
Line 123:                <asp:BoundField DataField="ramal" HeaderText="Ramal" />

Source File: c:\Users\Admin\Documents\Visual Studio 2012\Projects\Teste\Teste\RowCommand.aspx    Line: 121 


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Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.34280