How to implement custom filtering in WinForms MultiColumnComboBox?

void multiColumnComboBox1_KeyUp(object sender, KeyEventArgs e)

{

   selectedRows.Clear();

   if (this.multiColumnComboBox1.TextBox.Text == "")

   {

      this.multiColumnComboBox1.DataSource = dt;

   }

   else

   {

      keypressed = e.KeyData.ToString().ToLower();

      word = this.multiColumnComboBox1.Text;

      for (int i = 0; i <= this.multiColumnComboBox1.Items.Count - 1; i++)

      {

          object matchedRows = (this.multiColumnComboBox1.Items[i] as DataRowView).Row[0];

          if (matchedRows != null && matchedRows.ToString().ToLower().Contains(word.ToString().ToLower()))

          {

             selectedRows.Add(this.multiColumnComboBox1.Items[i] as DataRowView);

          }

       }

       if (selectedRows.Count > 0)

       {

           this.multiColumnComboBox1.DataSource = selectedRows;

           this.multiColumnComboBox1.DroppedDown = false;

           this.multiColumnComboBox1.DroppedDown = true;

           this.multiColumnComboBox1.TextBox.Text = word;

           this.multiColumnComboBox1.SelectionStart = this.multiColumnComboBox1.Text.Length;

           this.multiColumnComboBox1.TextBox.SelectionLength =    this.multiColumnComboBox1.Text.Length;

       }

       else

       {

           this.multiColumnComboBox1.DataSource = dt;

       }

}

Private Sub multiColumnComboBox1_KeyUp(ByVal sender As Object, ByVal e As KeyEventArgs)

    selectedRows.Clear()

    If Me.multiColumnComboBox1.TextBox.Text = "" Then

       Me.multiColumnComboBox1.DataSource = dt

    Else

       keypressed = e.KeyData.ToString().ToLower()

       word = Me.multiColumnComboBox1.Text

    For i As Integer = 0 To Me.multiColumnComboBox1.Items.Count - 1

       Dim matchedRows As Object = (TryCast(Me.multiColumnComboBox1.Items(i), DataRowView)).Row(0)

        If matchedRows IsNot Nothing AndAlso matchedRows.ToString().ToLower().Contains(word.ToString().ToLower()) Then

          selectedRows.Add(TryCast(Me.multiColumnComboBox1.Items(i), DataRowView))

        End If

    Next i

    If selectedRows.Count > 0 Then

      Me.multiColumnComboBox1.DataSource = selectedRows

      Me.multiColumnComboBox1.DroppedDown = False

      Me.multiColumnComboBox1.DroppedDown = True

      Me.multiColumnComboBox1.TextBox.Text = word

      Me.multiColumnComboBox1.SelectionStart = Me.multiColumnComboBox1.Text.Length

      Me.multiColumnComboBox1.TextBox.SelectionLength = Me.multiColumnComboBox1.Text.Length

    Else

      Me.multiColumnComboBox1.DataSource = dt

    End If

  End If

End Sub