I need to retreive the DataKey of the selected row in a GridView. Here's my situation :

In a previous post ( http://forums.asp.net/t/1166794.aspx ), I asked help to add a clickable image in a gridview. The solution proposed in that post works and I did it, so I set that post resolved. Now, my problem is to access the DataKey. I know that, usually, I need to use the CommandArgument to retreive the index of the row, and then retreive different value, including the DataKey property (wich is the one I look for). Curiously, the CommandArgument passed in the OnRowCommand event is set to NULL. I trace it in the debugger, in the RowDataBound event, and it look ok at this stage; the command argument of the row having the index number that I can use further in the OnRowCommand event. But no matter if I let the default value of if I force one, I still get a null in the post back (OnRowCommand event).

So, I suppose that it my problem is related with the solution I use ( http://forums.asp.net/t/1166794.aspx ), because the other clickable column forcing a postback passes a good CommandArgument (the index of the row). So, do someone have an idea what I should do to get the index from the CommandArgument ?

Actually, the only way I found to get something from the CommandArgument parameter is to set it in the aspx page like this :

<asp:TemplateField>

<ItemTemplate>

<asp:LinkButton ID="btnCopy" runat="server" CausesValidation="False" CommandName="CopyButton" CommandArgument='<%# Eval("DATAFIELD1")+ ";" + Eval("DATAFIELD2")%>'>

<asp:Image ID="imgBtnCopy" runat="server" imageUrl="~/Common/Images/copy.gif" />

</asp:LinkButton>

</ItemTemplate>

In this exemple, DATAFIELD1 and DATAFIELD2 are data column. With that solution, my problem is that I dont always have the key display in the data column. Sometime, as an exemple, a table may have a primary key that I want to be hidden (ex : next number). I can put this key in the DataKey property ... but I dont know if I can send it back, with the CommandArgument, in the aspx file using a syntaxe like CommandArgument='<%... %>'

Thanks for help !

Finaly, I found a solution. If someone has a better one, please send it.

So, to solve my problem of a NULL CommandArgument, I found a way to set the index of the row selected. After, I use the index as normal to access the DataKeys. 

<asp:TemplateField>

<ItemTemplate>

<asp:LinkButton ID="btnCopy" runat="server" CausesValidation="False" CommandName="CopyButton" CommandArgument='<%# GridView1.Rows.Count.ToString() %>'>

<asp:Image ID="imgBtnCopy" runat="server" imageUrl="~/Common/Images/copy.gif" />

</asp:LinkButton>

</ItemTemplate>

</asp:TemplateField>

Hello, 

You can use the Click event of the linkbutton to get the row information from inside the gridview (if this is what you mean). 

For example:

    protected void LinkButton1_Click(object sender, EventArgs e)
    {
        LinkButton btn = (LinkButton)sender;
        GridViewRow row = (GridViewRow)btn.NamingContainer;
        Response.Write("Row Index of Link button: " + row.RowIndex +
                       "DataKey value:" + GridView1.DataKeys[row.RowIndex].Value.ToString());
    }

        <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataKeyNames="ID" DataSourceID="SqlDataSource1">
            <Columns>
                <asp:BoundField DataField="ID" HeaderText="ID" InsertVisible="False" ReadOnly="True"  SortExpression="ID" />
                <asp:BoundField DataField="NAME" HeaderText="NAME" SortExpression="NAME" />
                <asp:BoundField DataField="PHONE" HeaderText="PHONE" SortExpression="PHONE" />
                <asp:BoundField DataField="CITY" HeaderText="CITY" SortExpression="CITY" />
                <asp:BoundField DataField="ABBR" HeaderText="ABBR" SortExpression="ABBR" />
                <asp:TemplateField>
                    <ItemTemplate>
                        <asp:LinkButton ID="LinkButton1" runat="server" OnClick="LinkButton1_Click">Get Row Info</asp:LinkButton>
                    </ItemTemplate>
                </asp:TemplateField>
            </Columns>
        </asp:GridView>

Hope this helps. 

Thanks CSharpSean,

 I figure there's a way to get it with the Click event, but I didn't now how. Im pretty sure this information will serve me one day, but for now, I will keep my solution because I like to have all the postback, initiated by a click, in the OnRowCommand event.

Thanks again

I like MSchumacher´s solution for this and I have used the same method, previously I achieved it using the RowDataBound event

protected void _grid_RowDataBound(object sender, GridViewRowEventsArgs e) {

        if (e.Row.RowType == DataControlRowType.DataRow) {

              //Button button = e.Row.Cells[0].FindControls("btnEdit") as ImageButton;

             button.CommandArgument = e.Row.RowIndex.ToString()

      }

}