get the value of checkboxcolumn in datagrid

[Ahmed]

hiiii,, i want to get the value of checkboxcolumn in datagrid wpf

i try this code

if (item.boolCol == true)
              {
                  MessageBox.Show("fail");
              }
              else
              {
                  MessageBox.Show("success");

              }

but don't take the changed value but take the same value of the my itemsourse 

[Ahmed]

i try this code  

    foreach (spShowTotal_Result item in dgShowStudent.ItemsSource) { bool? check = ((CheckBox)dgShowStudent.Columns[0].GetCellContent(item)).IsChecked; }

but this error is appear Unable to cast object of type 'System.Windows.Controls.ContentPresenter' to type 'System.Windows.Controls.CheckBox'.