When using a GridView, SelectedIndex is always 0 when using custom select button

Question

When clicking the select button in gvSquid2, x gets a valid and correct value. When clicking the select button in gvSquid, I get an ArgumentOutOfRange Exception because gv.SelectedIndex=0. Additionally, gv.SelectedDataKey is null. How do I get the DataKey information? Putting it in a column is not acceptable, as it must be hidden from the user. Hiding the column is useless, because during DataBind(), the value is discarded. I ripped this example from Microsoft's website. What am I missing?

<asp:gridview ID="gvSquid2" DataSourceID="dsComments" AutoGenerateColumns="false" AutoGenerateSelectButton="true" DataKeyNames="ID" OnSelectedIndexChanged="gvSquid_SelectedIndexChanged" runat="server" EnableViewState="false">
    <Columns>
        <asp:BoundField DataField="Date" ReadOnly="true" HeaderText="Date" SortExpression="Date" />
        <asp:BoundField DataField="Comment" ReadOnly="true" HeaderText="Comment" SortExpression="Comment" />
        <asp:BoundField DataField="Username" ReadOnly="true" HeaderText="User" SortExpression="Username" />
    </Columns>
</asp:gridview> 

<asp:gridview ID="gvSquid" DataSourceID="dsComments" AutoGenerateColumns="false" DataKeyNames="ID" OnSelectedIndexChanged="gvSquid_SelectedIndexChanged" runat="server" EnableViewState="false">
  <Columns>
    <asp:CommandField ButtonType="Image" HeaderText="Select" ShowSelectButton="true" SelectImageUrl="~/includes/RedX.jpg" />
    <asp:BoundField DataField="Date" ReadOnly="true" HeaderText="Date" SortExpression="Date" />
    <asp:BoundField DataField="Comment" ReadOnly="true" HeaderText="Comment" SortExpression="Comment" />
    <asp:BoundField DataField="Username" ReadOnly="true" HeaderText="User" SortExpression="Username" />
  </Columns>
</asp:gridview> 

protected void gvSquid_SelectedIndexChanged(object sender, EventArgs e) {
    string x;
    x = gvSquid.DataKeys[gvSquid.SelectedIndex].Value.ToString();
} 

Answer 1

I figured it out. EnableViewState="true" has to be set. Once I changed that, suddenly the DataKeys appeared.

This question helped.

Answer 2

Try using the SelectedRow of the grid view to get to the RowIndex, like this:

protected void gvSquid_SelectedIndexChanged(object sender, EventArgs e) 
{
    string x;
    GridViewRow theGridViewRow = gvSquid.SelectedRow;
    x = gvSquid.DataKeys[theGridViewRow.RowIndex].Value.ToString();
}