Add a hiddenfield into your page
<asp:HiddenField ID="HiddenField1" runat="server" />
Use the Id(use corresponding column name instead of Id) of the records as the CommandArgument of Cancel button
<asp:Button ID="btncancel" runat="server" CommandArgument='<%#Eval("Id") %>' Text="Cancel" />
Then on clicking the cancel button it calls the gridviews rowcommand function. In that function keep the CommandArgument value in the hidden field as follows
protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
{
HiddenField1.Value = e.CommandArgument.ToString();
}
Then on clicking the OK button, it calls the click event. In that function remove the Item from the List and then bind the list again to the gridview
protected void btnOK_Click(object sender, ButtonClickEventArgs e)
{
string id = HiddenField1.Value;
//use this id to remove the data from the List
// bind the gridview
}