title: checkbox column value in radGridview
body: <p>I'm working with radGridView and I'm building the data assigned to it, I mean I'm creating the columns and the rows (not assigning to datasource). After adding the data to the grid I add a checkbox column that should be used to check multi rows (same as muti-select idea but using checkboxcolumn), </p>
  
  <p>so this column is not bind to any data, its value should be assigned during runtime.
  When I try to retrieve this checkbox column value it turned out to be null even if it's checked, I used this method to update its value, but it didn't work out:</p>
  
  <pre><code>   private void radGridView1_ValueChanged(object sender, EventArgs e)
          {
              if(radGridView1.CurrentCell!=null)
                  if(radGridView1.CurrentCell.ColumnInfo is GridViewCheckBoxColumn)
                      radGridView1.TableElement.Update(GridUINotifyAction.DataChanged);
          }
  </code></pre>
  
  <p>What should I do to get the value of the checkbox column not on valueChanged but on another button click?</p>