I have blogged before about this Excel Nuget package where you don’t need to use interop and have Excel installed on the server. And my journey to start this Azure Function. This is because the most recent Excel format uses xml under the cover in a zipped file stored as a file with an xlsx extension. Since you do not have hard disk access in a serverless environment like Azure Functions you need to generate the Excel in memory (or store stuff in blob storage). I chose the in memory to leave no footprints or take up space in the cloud.

I wanted to use an Azure function to have it run in the cloud. Not being dependent on a Server which needs updates, reboots etc. Since the database already is in the Azure Cloud (Azure SQL) this seems a good/perfect fit.

I got the option to go for Azure function v1 or v2 which is in preview. So this was a nice opportunity to use the v2 and .Net Core/Standard. https://docs.microsoft.com/en-us/azure/azure-functions/functions-versions

The v2 also has support for the Office365 Graph. But that was out of (my) scope.

I took a timer based project because I wanted it to send an overview of invoices on a monthly basis. The Timer based project has a timer as data annotation based on CRON scheduling. There is however a small difference. Instead of 5 “fields” the Azure function has 6. It also let’s you schedule the seconds.


So not just: minutes, hours, day of month, month, day of week, year but seconds, minutes, hours, day of month, month, day of week, year. Of course the order is really important. https://docs.microsoft.com/en-us/azure/azure-functions/functions-bindings-timer#cron-expressions

I used this Nuget for the Excel export https://www.nuget.org/packages/EPPlus/

it has .Net Core support and will work perfectly.

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.IO;
using System.Net;
using System.Net.Mail;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Host;
using OfficeOpenXml;

namespace MonthlyMailInvoices
    public static class Function1
        public static void Run([TimerTrigger("10 0 0 1 * *")]TimerInfo myTimer, TraceWriter log)
            log.Info($"C# Timer trigger function executed at: {DateTime.Now}");

            var com = new SqlCommand("SELECT * FROM [dbo].[INVOICES] where invoicedate > @startdt and invoicedate < @enddt");

            com.Parameters.AddWithValue("startdt", DateTime.Now.AddMonths(-1));
            com.Parameters.AddWithValue("enddt", DateTime.Now.AddDays(-1));

            var dt = new DataTable();

            using (var con = new SqlConnection("connectionstring goes here"))
                com.Connection = con;
                var da = new SqlDataAdapter(com);

                log.Info($"start: {DateTime.Now.AddMonths(-1)} and end { DateTime.Now.AddDays(-1) } gave {dt.Rows.Count}");

            using (var wb = new ExcelPackage())
                wb.Workbook.Worksheets.Add("Our company");
                var ws = wb.Workbook.Worksheets[0];

                FillData(ws, dt, "Our company B.V.");

                var msg = new MailMessage();
                msg.Subject = "Montly invoices";
                msg.From = new MailAddress("the@cloud.com");
                msg.Body = $"Invoices from {DateTime.Now.AddMonths(-1)} to { DateTime.Now.AddDays(-1) } in the Excel attachment.";
                var ms = new MemoryStream(wb.GetAsByteArray());
                ms.Position = 0;

                //msg.Attachments.Add(new Attachment(ms, "Invoices.xlsx", "application/vnd.ms-excel"));
                msg.Attachments.Add(new Attachment(ms, "Invoices.xlsx", "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"));
                var smtp = new SmtpClient
                    Host = "smtp.gmail.com",
                    Port = 587,
                    EnableSsl = true,
                    Credentials = new NetworkCredential("my@gmailaccount.com", "incorrectpassword")

        private static void FillData(ExcelWorksheet ws, DataTable dt, string title)
            ws.Cells[1, 1].Value = title;

            ws.Cells[2, 1].Value = "Invoice nr";
            ws.Cells[2, 2].Value = "Invoice date";
            ws.Cells[2, 3].Value = "Amount inc. VAT";
            ws.Cells[2, 4].Value = "VAT";
            ws.Cells[2, 5].Value = "Amount exc. VAT";

            int row = 3;

            foreach (DataRow dr in dt.Rows)
                ws.Cells[row, 1].Value = dr[0].ToString();
                ws.Cells[row, 2].Value = dr[1].ToString();
                ws.Cells[row, 3].Value = dr[2].ToString();
                ws.Cells[row, 4].Value = dr[3].ToString();
                ws.Cells[row++, 5].Value = dr[4].ToString();

I could not test it locally because I had some issues with logins for my localdb. So I hit publish to deploy it on Azure. However republishing failed. I found the answer (as always) on StackOverflow. I had to add “MSDEPLOY_RENAME_LOCKED_FILES” and set it to 1 (true).


Tony gave the correct solution.

I also had issues with the Excel generating in memory and having the Memorystream to a byte array and providing the right Mime type. Found that too on SO.

The last bit was to automate deployment. I had my code in VSTS (git) and configured a CI/CD pipeline (build + release) But had issues to grant myself (personal account) global admin rights from our company account in order to be able to access Azure resources to deploy. It was a matter of time before the Azure rights/roles changes are active. It’s a nice small serverless function which you can (should) add to source control and ci/cd to automate the latest builds to a test or production environment in the cloud.

Good luck!

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