Assigning and accessing multiple values for DataKeyNames on a GridView

Multiple DB column values can be assigned to the DataKeyNames attribute of a GridView, and accessed in the code-behind as follows:

aspx markup:
asp:GridView ID="gv1" runat="server"
DataSourceID="ods1"
DataKeyNames="pk_parent_id, fk_child_id"
OnRowDataBound="gv1_RowDataBound"

code-behind:

protected void gv1_RowDataBound(object sender, GridViewRowEventArgs e)
{
int childId = (int)(gv1.DataKeys[e.Row.DataItemIndex].Values["fk_child_id"]);
}


protected void btn1_Click(object sender, EventArgs e)
{
foreach (GridViewRow row in gv1.Rows)
{
int childId = (int)(gv1.DataKeys[row.RowIndex].Values["fk_child_id"]);
}
}