在C＃中为大型数据创建Excel

Question

I am trying to generate excel sheet for a large data about a million records. But when using the below code I am getting nothing. The code hangs up after line : wb.SaveAs(MyMemoryStream); . I am using closed XML for the purpose. Can you please guide what can be done to save large data as excel.

My Code:

private void DownloadExcel()
    {
        String Attachment = "attachment; filename=TestFile.xlsx";
        Response.ClearContent();
        DataTable dt = ds.Tables[0];


        using (XLWorkbook wb = new XLWorkbook())

        {
            wb.Worksheets.Add(dt, "Data");
            wb.Style.Font.FontName = "Courier New";
            // wb.Cell("A1:A+" + colCount + "").Style.Font.Bold = true;
            Response.Clear();
            Response.Buffer = true;
            Response.Charset = "";
            Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
            Response.AddHeader("content-disposition", Attachment);
            using (MemoryStream MyMemoryStream = new MemoryStream())
            {
                wb.SaveAs(MyMemoryStream);
                MyMemoryStream.WriteTo(Response.OutputStream);
                Response.Flush();
                Response.SuppressContent = true;  // Gets or sets a value indicating whether to send HTTP content to the client.
                HttpContext.Current.ApplicationInstance.CompleteRequest();
            }
        }
    }

I am ok with any other library as well to save the data as XML.

Answer 1

You can try any of below approaches:

Approach 1: First you need to create the template of the excel and then use the below function. It will create new excel using your template and inserts data into excel using ACE.OLEDB. It will be much faster but you don't have control over formatting.

   public static void CopyDataTableToExcel(DataTable dtExcel, String excelOutputTemplate, string outExcelPath)
    {
        File.Copy(excelOutputTemplate, outExcelPath, true);

        string qryFieldName = "";
        string qryFieldForCreate = "";
        string qryFieldValue = "";
        string qryFieldValueTemp = "";
        string qryInsert = "";

        for (int i = 0; i < dtExcel.Columns.Count; i++)
        {
            qryFieldName = qryFieldName + (qryFieldName.Trim() != "" ? ", " : "") + "[" + dtExcel.Columns[i].ColumnName + "]";
            qryFieldForCreate = qryFieldForCreate + (qryFieldForCreate.Trim() != "" ? ", " : "") +
                 "[" + dtExcel.Columns[i].ColumnName + "] varchar(255)";
        }

        // Establish a connection to the data source.
        System.Data.OleDb.OleDbConnection objConn = new System.Data.OleDb.OleDbConnection(
            "Provider=Microsoft.ACE.OLEDB.12.0;Data Source='" + outExcelPath + "';Extended Properties=\"Excel 12.0;HDR=YES;\"");
        objConn.Open();

        // Add two records to the table named 'MyTable'.
        System.Data.OleDb.OleDbCommand objCmd = new System.Data.OleDb.OleDbCommand();
        objCmd.Connection = objConn;

        qryInsert = "Create table InventorySheet (" + qryFieldForCreate + ")";
        objCmd.CommandText = qryInsert;
        objCmd.ExecuteNonQuery();

        for (int i = 0; i < dtExcel.Rows.Count; i++)
        {
            qryFieldValue = "";
            for (int j = 0; j < dtExcel.Columns.Count; j++)
            {
                qryFieldValueTemp = dtExcel.Rows[i][j].ToString();
                if (qryFieldValueTemp.Length > 255)
                {
                    qryFieldValueTemp = qryFieldValueTemp.Substring(qryFieldValueTemp.Length - 255);
                }
                qryFieldValue = qryFieldValue + (qryFieldValue.Trim() != "" ? ", '" : "'") + qryFieldValueTemp.Replace("'", "''") + "'";
            }

            //qryInsert = "Insert into [Sheet1$] Values (" + qryFieldValue + ")";
            qryInsert = "Insert into InventorySheet (" + qryFieldName + ") Values (" + qryFieldValue + ")";
            objCmd.CommandText = qryInsert;
            objCmd.ExecuteNonQuery();
        }

        // Close the connection.
        objConn.Close();
        MessageBox.Show("Exported successfully.");
    }

Approach 2: Serialize the data table into xml:

DataTable dtJobMetaData = yourDataSet.Tables["PDF"];
dtJobMetaData.WriteXml(xmlPath);