关闭弹出消息后如何将焦点重新设置到错误元素？

Question

I have a DataGrid that has a DataGridTemplateColumn contains an editable TextBox control. I also register LostFocus event in xaml using EventTrigger and InvokeCommandAction.

For example: My grid has two rows, when I click the cell of the first row to edit something, if I enter some invalid values the press Tab or Enter key to focus out of editing cell, I have to do the following tasks:

1. Make the border of that cell is Red
2. Show an error message popup (just contains a message label and a close button)
3. After the above popup closed, set focus to that error cell and put a pointer to textbox inside it for user to input again until they enter a valid value

About No.1 & 2 I have done but I don't know how to do with No.3. Current behavior is when the popup closed, it automatically focus to cell of the next row instead of previous error cell.

Can anyone help me? Thank you.

Answer 1

Finally, I found a way can resolve my issue, that is using Dispatcher object to invoke a delegate like this:

var focusingElement = (System.Threading.ThreadStart)delegate { element.Focus(); };
Application.Current.Dispatcher.BeginInvoke(focusingElement);

Where is element is a type of FrameworkElement or UIElement object. In my case that is TextBox control.