.NET (Core and Framework)

<br />
private void dataEntryBehaviour(object sender, KeyEventArgs e)<br />
		{<br />
			if (e.KeyCode == Keys.Enter || e.KeyCode == Keys.Down)<br />
			{<br />
//				e.KeyCode = Keys.Down;	//to avoid the 1st input character disappearing bug<br />
										//NOT ALLOWED - READ ONLY!<br />
<br />
				//SuppressKeyPress is used to keep ENTER from being heard<br />
				e.SuppressKeyPress = true;	//this also sets e.Handled to true<br />
				this.SelectNextControl((Control)sender, true, true, true, true);<br />
			}<br />
			else if (e.KeyCode == Keys.Up)<br />
			{<br />
				e.SuppressKeyPress = true;	//this also sets e.Handled to true<br />
				this.SelectNextControl((Control)sender, false, true, true, true);<br />
			}<br />
		}<br />

<br />
Attempting to type "3056667777" results:<br />
<br />
Without setting MaskedTextBox.SelectionStart = 1, "(056) 667-777_"<br />
<br />
With setting MaskedTextBox.SelectionStart = 1, "(_05) 666-7777"<br />
<br />
So, essentially, to get the results I want I'd have to not set MaskedTextBox.SelectionStart = 1, and type "33056667777".<br />

<code>
public class DataGridViewColorComboBoxCell : DataGridViewComboBoxCell
{
  private Color[] colorItems = { Color.Red, Color.Green, Color.Blue };
  Color c;
  protected int inMargin;
  protected int boxWidth;
  public DataGridViewColorComboBoxCell():base()
  {
    inMargin = 2;
    boxWidth = 3; 
    for (Int32 i = 0; i < colorItems.Length; i++)
    {
      this.Items.Add(colorItems[i].ToArgb().ToString());
    }
  }
  protected override object GetFormattedValue(
    object value,
    int rowIndex,
    ref DataGridViewCellStyle cellStyle,
    System.ComponentModel.TypeConverter valueTypeConverter,
    System.ComponentModel.TypeConverter formattedValueTypeConverter,
    DataGridViewDataErrorContexts context)
  {
    return (value);
  }
  public override Type EditType
  {
    get {return typeof(DataGridViewColorComboEditingControl);}
  }
  public override void InitializeEditingControl(
    int rowIndex, 
    object initialFormattedValue, 
    DataGridViewCellStyle dataGridViewCellStyle)
  {
    base.InitializeEditingControl(
      rowIndex, 
      initialFormattedValue, 
      dataGridViewCellStyle);
    DataGridViewColorComboEditingControl ctrl = 
      DataGridView.EditingControl as DataGridViewColorComboEditingControl;
    ctrl.ownerCell = this;
  }
  protected override void Paint(
    Graphics graphics, 
    Rectangle clipBounds, 
    Rectangle cellBounds, 
    int rowIndex, 
    DataGridViewElementStates elementState, 
    object value, 
    object formattedValue, 
    string errorText, 
    DataGridViewCellStyle cellStyle, 
    DataGridViewAdvancedBorderStyle advancedBorderStyle, 
    DataGridViewPaintParts paintParts)
  {
    base.Paint(
      graphics, 
      clipBounds, 
      cellBounds, 
      rowIndex, 
      elementState, 
      value, 
      formattedValue, 
      errorText, 
      cellStyle, 
      advancedBorderStyle, 
      paintParts);
    if (formattedValue != null && formattedValue.ToString() != "")
    {
      c = Color.FromArgb(Convert.ToInt32((string)formattedValue));
      Graphics g = graphics;
      g.FillRectangle(new SolidBrush(c), 
        cellBounds.X + this.inMargin, 
        cellBounds.Y + this.inMargin, 
        cellBounds.Width - (2 * this.inMargin + 1), 
        cellBounds.Height - (2 * this.inMargin + 1));
      g.DrawRectangle(Pens.Black, 
        cellBounds.X + this.inMargin, 
        cellBounds.Y + this.inMargin, 
        cellBounds.Width - (2 * this.inMargin + 1), 
        cellBounds.Height - (2 * this.inMargin + 1));
    }
  }
}
</code>