How to use "content disposition attachment" in OpenXml - asp.net-mvc

Question

I have an ASP.NET MVC 4 site that creates an Excel file using OPEN XML SDK. My controller method generates the OPEN XML Excel document and is downloading it.
But the user should see the Excel file in the browser.
I know
Response.AddHeader("content-disposition", "attachment; filename=" + fileName + "");
is responsible for it. But I don't know how to implement this in openXnl method. I am not using http response here. Or how can I use it? Please help me on this
This is my Excel generating method, and I tried to implement AddHeader "content-disposition" but nothing works:
public static void GenerateExcelOpenXML(string FolderPath, DataSet tableSet)
{
WorkbookPart wBookPart = null;
var datetime = DateTime.Now.ToString().Replace("/", "_").Replace(":", "_");
string FilePath = FolderPath + "Report_" + datetime + ".xlsx";
using (SpreadsheetDocument spreadsheetDoc = SpreadsheetDocument.Create(FilePath, SpreadsheetDocumentType.Workbook))
{
wBookPart = spreadsheetDoc.AddWorkbookPart();
wBookPart.Workbook = new Workbook();
uint sheetId = 1;
spreadsheetDoc.WorkbookPart.Workbook.Sheets = new Sheets();
Sheets sheets = spreadsheetDoc.WorkbookPart.Workbook.GetFirstChild<Sheets>();
WorkbookStylesPart wbsp = wBookPart.AddNewPart<WorkbookStylesPart>();
wbsp.Stylesheet = CreateStylesheet();
wbsp.Stylesheet.Save();
foreach (DataTable table in tableSet.Tables)
{
WorksheetPart wSheetPart = wBookPart.AddNewPart<WorksheetPart>();
Sheet sheet = new Sheet() { Id = spreadsheetDoc.WorkbookPart.GetIdOfPart(wSheetPart),
SheetId = sheetId, Name = table.TableName };
sheets.Append(sheet);
SheetData sheetData = new SheetData();
wSheetPart.Worksheet = new Worksheet();
Row headerRow = new Row();
Columns columns = new Columns();
int ColumnNumber = 1;
foreach (DataColumn column in table.Columns)
{
Cell cell = new Cell();
cell.DataType = CellValues.String;
cell.CellValue = new CellValue(column.ColumnName);
cell.StyleIndex = 2;
headerRow.AppendChild(cell);
Column column1 = new Column();
column1.Width = 30;
column1.Min = Convert.ToUInt32(ColumnNumber);
column1.Max = Convert.ToUInt32(ColumnNumber);
column1.CustomWidth = true;
columns.AppendChild(column1);
ColumnNumber = ColumnNumber + 1;
}
wSheetPart.Worksheet.AppendChild(columns);
sheetData.AppendChild(headerRow);
foreach (DataRow dr in table.Rows)
{
Row row = new Row();
foreach (DataColumn column in table.Columns)
{
Cell cell = new Cell();
cell.DataType = CellValues.String;
cell.CellValue = new CellValue(dr[column].ToString());
cell.StyleIndex = 1;
row.AppendChild(cell);
}
sheetData.AppendChild(row);
}
sheetId++;
wSheetPart.Worksheet.AppendChild(sheetData);
// sheetData.AddHeader("content-disposition", "attachment; filename=" + fileName + "");
// how can I implement here?
}
}
}