I have trouble reading the field. I have tried in different ways but still can not. I want to read the value that the user selected the following 3 values.
Code in X
I guess you want to enable multi selection in the combobox inside DataGridComboBoxColumn. Following code project does the same.
http://www.codeproject.com/Articles/21085/CheckBox-ComboBox-Extending-the-ComboBox-Class-and