title: DataGrid CheckBox can't be checked
body: <p>I got a problem with datagrid and DataGridCheckBoxClumn. First of all im creating struct for datagrid items:</p>
  
  <pre><code>public struct taxRateFromDatabase
  {
      public int rate { get; set; }
      public string mark { get; set; }
      public CheckBox c { get; set; }
  }
  </code></pre>
  
  <p>And after that in my class adding columns, bindings etc:</p>
  
  <pre><code>    StackPanel tSp = new StackPanel();
      DataGrid taxRateDataGrid = new DataGrid();
      DataGridTextColumn col0 = new DataGridTextColumn();
      DataGridTextColumn col1 = new DataGridTextColumn();
      DataGridCheckBoxColumn col2 = new DataGridCheckBoxColumn();
      Binding b = new Binding("checkBox");
      b.Mode = BindingMode.TwoWay;
  
      b.UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged;
  
      taxRateDataGrid.Columns.Add(col0);
      taxRateDataGrid.Columns.Add(col1);
      taxRateDataGrid.Columns.Add(col2);
  
      col0.Binding = new Binding("rate");
      col1.Binding = new Binding("mark");
      col2.Binding = b;
  
      CheckBox c = new CheckBox();
      c.Content = "a";
  
  
      col0.Header = "Stawka";
      col1.Header = "Oznaczenie";
      col2.Header = "Status";
  
  
  
      taxRateDataGrid.Items.Add(new taxRateFromDatabase { rate = 0, mark = "E", c = c });
      taxRateDataGrid.Items.Add(new taxRateFromDatabase { rate = 1, mark = "G", c = c });
  </code></pre>
  
  <p>Problem is that I cant really check/uncheck that checkbox i have just added.
  I have tried also without checkbox in struct definition (just empty datagridcheckboxcolumn), but that also doesnt work. Im creating it in class which will return datagrid so i cant really acces xaml.</p>
  
  <p>Any sugestions will be appreciated ;)</p>