Downloaded Excel sheet is corrupt

        System.Web.HttpResponse response = System.Web.HttpContext.Current.Response;
        response.Clear();
        response.Buffer = true;
        response.Charset = "charset=utf-8";
        response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
        response.AddHeader("content-disposition", "attachment;filename=ExcelData.xlsx");
        response.BinaryWrite(File.ReadAllBytes(templateDir + "myFile.xlsx"));
        response.Flush();
        response.End();

The Excel File that is downloaded after the http request made to the Controller method is corrupted. The data/text is Excel file is not readable and modified. I am using the above mentioned code. Please help me to resolve this issue.