How to export the formula cells with formatted text only and cell style to excel from grid?

//Creating Custom Class
private class GridExcelConverterControlAdv : GridExcelConverterControl
{
    public GridExcelConverterControlAdv()
    {
    }
    protected override void ExportCellToExcel(GridStyleInfo gridCell, IRange range)
    {
        base.ExportCellToExcel(gridCell, range);
        switch (gridCell.CellType)
        {
            case "FormulaCell":
                if (gridCell.Text.Length != 0 && gridCell.Text[0] == '=')
                {
                    //To set the text alone in the formula cell.
                    range.Value = gridCell.FormattedText;
                }
                break;
        }
    }
}
 
private void exportBtn_Click(object sender, EventArgs e)
{
    GridExcelConverterControlAdv excelConverter = new GridExcelConverterControlAdv();
    if (saveFileDialog.ShowDialog() == System.Windows.Forms.DialogResult.OK)
    {
        strFileLocation = saveFileDialog.FileName;
        //To export the grid to excel with style and format.
        excelConverter.GridToExcel(gridControl1, sheet, ConverterOptions.Default);
    }
}

'Custom class
Private Class GridExcelConverterControlAdv
 Inherits GridExcelConverterControl 
 Public Sub New()
 End Sub
 Protected Overrides Sub ExportCellToExcel(ByVal gridCell As GridStyleInfo, ByVal range As IRange)
  MyBase.ExportCellToExcel(gridCell, range)
  Select Case gridCell.CellType
   Case "FormulaCell"
    If gridCell.Text.Length <> 0 AndAlso gridCell.Text(0) = "="c Then
     'To set the text alone in the formula cell.
     range.Value = gridCell.FormattedText
    End If
  End Select
 End Sub
End Class
 
 
Private Sub exportBtn_Click(ByVal sender As Object, ByVal e As EventArgs) Handles button1.Click 
  Dim excelConverter As New GridExcelConverterControlAdv()
 If saveFileDialog.ShowDialog() = System.Windows.Forms.DialogResult.OK Then
  strFileLocation = saveFileDialog.FileName
  'To export the grid to excel with style and format.
  excelConverter.GridToExcel(gridControl1, sheet, ConverterOptions.Default)
 End If
End Sub