title: DataGridView DataSource contents duplicated
body: <p>If I go to select a new XML file and attach it as a <strong>datasource</strong> to the <strong>DataGridView</strong> it doesn't replace the grid contents but appends to it:</p>
  
  <pre><code>private void buttonSelectXML_Click(object sender, EventArgs e)
  {
      OpenFileDialog dlgFile = new OpenFileDialog();
  
      dlgFile.Title = "Select XML file";
      dlgFile.Filter = "XML files (*.xml)|*.xml";
      dlgFile.FilterIndex = 0;
      dlgFile.Multiselect = false;
      dlgFile.InitialDirectory = Path.GetDirectoryName(textBoxXML.Text);
      dlgFile.FileName = textBoxXML.Text;
  
      if (dlgFile.ShowDialog() == DialogResult.OK)
      {
          Properties.Settings.Default.XMLPath = dlgFile.FileName;
          textBoxXML.Text = dlgFile.FileName;
  
          dataSet.ReadXml(textBoxXML.Text);
          dataGridView.DataSource = dataSet.Tables[0];
      }
  }
  </code></pre>
  
  <p>What is the right way to <strong>replace</strong> the current grid content with the new XML datasource rather than <strong>append</strong>?</p>
  
  <p>Thanks.</p>