private void ButUpdate_Click(object sender, EventArgs e) { if (IsFormComplete) { int index = ArgumentContainer.IndexOf(SelectedArgument.Value); ArgumentContainer.RemoveAt(index); ArgumentContainer.Insert(index, new CustomAttributeNamedArgument(ItemName.Text, AttributeArgumentEditor.SelectedArgument)); DialogResult = DialogResult.OK; } else { DialogResult = DialogResult.None; } }