bulk data export to excel and download in ashx file - asp.net

Question

I have an asp.net application in which I have a js file and an ashx file. Here in a download button click Im calling handler file in ajax call and retrieving sql table data in a json formatted string/data table and Im trying to export json formated string/data table to excel/csv file and download it. Please help me to find a solution. (Need a solution which help to export large amount of data and download)
I tried the below code but its not downloading excel file.
public void ProcessRequest(HttpContext context)
{
context.Response.AddHeader("content-disposition", "attachment; filename=FileName.xls");
context.Response.ContentType = "application/csv";
HttpResponse response = context.Response;
string exportContent = ExportToSpreadsheet(JsonStringToDataTable(GetDataFromTable()),'excelfilename');
response.Write(exportContent);
context.Response.End();
}
public DataTable JsonStringToDataTable(string jsonString)
{
DataTable dt = new DataTable();
string[] jsonStringArray = Regex.Split(jsonString.Replace("[", "").Replace("]", ""), "},{");
List<string> ColumnsName = new List<string>();
foreach (string jSA in jsonStringArray)
{
string[] jsonStringData = Regex.Split(jSA.Replace("{", "").Replace("}", ""), ",");
foreach (string ColumnsNameData in jsonStringData)
{
try
{
int idx = ColumnsNameData.IndexOf(":");
string ColumnsNameString = ColumnsNameData.Substring(0, idx - 1).Replace("\"", "");
if (!ColumnsName.Contains(ColumnsNameString))
{
ColumnsName.Add(ColumnsNameString);
}
}
catch (Exception ex)
{
//throw new Exception(string.Format(ex.Message + "Error Parsing Column Name : {0}", ColumnsNameData));
throw ex;
}
}
break;
}
foreach (string AddColumnName in ColumnsName)
{
dt.Columns.Add(AddColumnName);
}
foreach (string jSA in jsonStringArray)
{
string[] RowData = Regex.Split(jSA.Replace("{", "").Replace("}", ""), ",");
DataRow nr = dt.NewRow();
foreach (string rowData in RowData)
{
try
{
int idx = rowData.IndexOf(":");
string RowColumns = rowData.Substring(0, idx - 1).Replace("\"", "");
string RowDataString = rowData.Substring(idx + 1).Replace("\"", "");
nr[RowColumns] = RowDataString;
}
catch (Exception ex)
{
continue;
}
}
dt.Rows.Add(nr);
}
return dt;
}
private static string GetDataFromTable()
{
string returnValue = string.Empty;
var serializer = new JavaScriptSerializer { MaxJsonLength = Int32.MaxValue };
try
{
var result = //get data from sql table;
returnValue = serializer.Serialize(result);
}
catch (Exception e)
{
returnValue = serializer.Serialize(e.Message);
}
return returnValue;
}
public string ExportToSpreadsheet(DataTable table, string name)
{
string res = string.Empty;
try
{
//var resp = Response;
System.Web.HttpResponse resp = System.Web.HttpContext.Current.Response;
resp.Clear();
if (table != null)
{
foreach (DataColumn column in table.Columns)
{
resp.Write(column.ColumnName + ",");
}
}
resp.Write(Environment.NewLine);
if (table != null)
{
foreach (DataRow row in table.Rows)
{
for (int i = 0; i < table.Columns.Count; i++)
{
resp.Write(row[i].ToString().Replace(",", string.Empty) + ",");
}
resp.Write(Environment.NewLine);
}
}
res = "successfully downloaded";
resp.ContentType = "text/csv";
resp.AppendHeader("Content-Disposition", "attachment; filename=" + name + ".csv");
// resp.End();
}
catch(Exception ex)
{
res = ex.Message;
}
return res;
}

Answer 1

Start using a specialized libary like EPPlus. It will create real Excel files.
private void exportToExcel(DataTable dataTable)
{
using (ExcelPackage excelPackage = new ExcelPackage())
{
//create the worksheet
ExcelWorksheet worksheet = excelPackage.Workbook.Worksheets.Add("Sheet 1");
//load the datatable into the sheet, with headers
worksheet.Cells["A1"].LoadFromDataTable(dataTable, true);
//send the file to the browser
byte[] bin = excelPackage.GetAsByteArray();
Response.ClearHeaders();
Response.Clear();
Response.Buffer = true;
Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
Response.AddHeader("content-length", bin.Length.ToString());
Response.AddHeader("content-disposition", "attachment; filename=\"ExcelDemo.xlsx\"");
Response.OutputStream.Write(bin, 0, bin.Length);
Response.Flush();
HttpContext.Current.ApplicationInstance.CompleteRequest();
}
}