How to make 'CTRL+~', shortcut key, to show formulas instead of values similar to Excel in the WinForms GridControl?

this.gridControl1.KeyDown += gridControl1_KeyDown;

//set the cellType as FormulaCell
this.gridControl1.TableStyle.CellType = GridCellTypeName.FormulaCell;
this.gridControl1.DrawCellDisplayText += gridControl1_DrawCellDisplayText;
void gridControl1_DrawCellDisplayText(object sender, GridDrawCellDisplayTextEventArgs e)
{
    if (this.gridControl1[e.Style.CellIdentity.RowIndex, e.Style.CellIdentity.ColIndex].CellType == "FormulaCell" & flag)
    {
        //draw the display text for the cell
        e.DisplayText = e.Style.CellValue.ToString();
    }
}        

void gridControl1_KeyDown(object sender, KeyEventArgs e)
{
    bool keydown = (e.Modifiers & Keys.Control) != Keys.None;
    Keys Key = e.KeyCode & Keys.KeyCode;

    //check whether the pressed key is Control with tilde or not
    if (Key == Keys.Oemtilde && keydown)
    {
        flag = !flag;
        this.gridControl1.Refresh();
        this.gridControl1.Model.Refresh();
    }
}

AddHandler Me.gridControl1.KeyDown, AddressOf gridControl1_KeyDown

'set the cellType as FormulaCell
Me.gridControl1.TableStyle.CellType = GridCellTypeName.FormulaCell
AddHandler Me.gridControl1.DrawCellDisplayText, AddressOf gridControl1_DrawCellDisplayText
void gridControl1_DrawCellDisplayText(Object sender, GridDrawCellDisplayTextEventArgs e)
    If Me.gridControl1(e.Style.CellIdentity.RowIndex, e.Style.CellIdentity.ColIndex).CellType Is "FormulaCell" & flag Then
        'draw the display text for the cell
        e.DisplayText = e.Style.CellValue.ToString()
    End If

void gridControl1_KeyDown(Object sender, KeyEventArgs e)
    Dim keydown As Boolean = (e.Modifiers And Keys.Control) <> Keys.None
    Dim Key As Keys = e.KeyCode And Keys.KeyCode
    'check whether the pressed key is Control with tilde or not
    If Key = Keys.Oemtilde AndAlso keydown Then
        flag = Not flag
        Me.gridControl1.Refresh()
        Me.gridControl1.Model.Refresh()
    End If