How to add more than one value in a Same datafield

I tried Your Given Code it shows error  as SilverlightUnhandledError...am using the following code for add datas to database
  private void btnSave_Click(object sender, RoutedEventArgs e)
        {
           
         MAGAZINE magazine = new MAGAZINE()
            magazine.MAG_ID = Int32.Parse(txtMagazineId.Text);
           //magazine.MAG_EDITION = textBox1.Text;
            magazine.MAG_EDITION = cmbMonth.SelectedItem.ToString() + "-" + cmbYear.SelectedItem.ToString();
                magazine.MAG_DESCRIPTION = txtDescription.Text;
            magazine.MAG_UPBY = Int32.Parse(txtUpdatedby.Text);
            magazine.MAG_UPDATE = DateTime.Parse(txtupdatedate.Text);
            magazine.MAG_FILE =System.Text.Encoding.UTF8.GetBytes(txtBook.Text);
            magazine.MAG_IMAGE = System.Text.Encoding.UTF8.GetBytes(txtCover.Text);
            magazine.MAG_ACTIVE = true;
            objectcontext.MAGAZINEs.Add(magazine);
            objectcontext.SubmitChanges(SubmitOperation_Callback,null);
            clearform();

        }
In this am using this(  magazine.MAG_EDITION = cmbMonth.SelectedItem.ToString() + "-" + cmbYear.SelectedItem.ToString();) for add combobox