Scott Hanselman

Converting an Excel Worksheet into a JSON document with C# and .NET Core and ExcelDataReader

March 06, 2019 Comment on this post [20] Posted in DotNetCore | Open Source
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Excel isn't a database, except when it isI've been working on a little idea where I'd have an app (maybe a mobile app with Xamarin or maybe a SPA, I haven't decided yet) for the easily accessing and searching across the 500+ videos from

HOWEVER. I don't have access to the database that hosts the metadata and while I'm trying to get at least read-only access to it (long story) the best I can do is a giant Excel spreadsheet dump that I was given that has all the video details.

This, of course, is sub-optimal, but regardless of how you feel about it, it's a database. Or, a data source at the very least! Additionally, since it was always going to end up as JSON in a cached in-memory database regardless, it doesn't matter much to me.

In real-world business scenarios, sometimes the authoritative source is an Excel sheet, sometimes it's a SQL database, and sometimes it's a flat file. Who knows?

What's most important (after clean data) is that the process one builds around that authoritative source is reliable and repeatable. For example, if I want to build a little app or one page website, yes, ideally I'd have a direct connection to the SQL back end. Other alternative sources could be a JSON file sitting on a simple storage endpoint accessible with a single HTTP GET. If the Excel sheet is on OneDrive/SharePoint/DropBox/whatever, I could have a small serverless function run when the files changes (or on a daily schedule) that would convert the Excel sheet into a JSON file and drop that file onto storage. Hopefully you get the idea. The goal here is clean, reliable pragmatism. I'll deal with the larger business process issue and/or system architecture and/or permissions issue later. For now the "interface" for my app is JSON.

So I need some JSON and I have this Excel sheet.

Turns out there's a lovely open source project and NuGet package called ExcelDataReader. There's been ways to get data out of Excel for decades. Literally decades. One of my first jobs was automating Microsoft Excel with Visual Basic 3.0 with COM Automation. I even blogged about getting data out of Excel into ASP.NET 16 years ago!

Today I'll use ExcelDataReader. It's really nice and it took less than an hour to get exactly what I wanted. I haven't gone and made it super clean and generic, refactored out a bunch of helper functions, so I'm interested in your thoughts. After I get this tight and reliable I'll drop it into an Azure Function and then focus on getting the JSON directly from the source.

A few gotchas that surprised me. I got a "System.NotSupportedException: No data is available for encoding 1252." Windows-1252 or CP-1252 (code page) is an old school text encoding (it's effectively ISO 8859-1). Turns out newer .NETs like .NET Core need the System.Text.Encoding.CodePages package as well as a call to System.Text.Encoding.RegisterProvider(System.Text.CodePagesEncodingProvider.Instance); to set it up for success. Also, that extra call to reader.Read at the start to skip over the Title row had me pause a moment.

using System;
using System.IO;
using ExcelDataReader;
using System.Text;
using Newtonsoft.Json;

namespace AzureFridayToJson
class Program
static void Main(string[] args)

var inFilePath = args[0];
var outFilePath = args[1];

using (var inFile = File.Open(inFilePath, FileMode.Open, FileAccess.Read))
using (var outFile = File.CreateText(outFilePath))
using (var reader = ExcelReaderFactory.CreateReader(inFile, new ExcelReaderConfiguration()
{ FallbackEncoding = Encoding.GetEncoding(1252) }))
using (var writer = new JsonTextWriter(outFile))
writer.Formatting = Formatting.Indented; //I likes it tidy
reader.Read(); //SKIP FIRST ROW, it's TITLES.
while (reader.Read())
//peek ahead? Bail before we start anything so we don't get an empty object
var status = reader.GetString(0);
if (string.IsNullOrEmpty(status)) break;








<iframe src="" width="960" height="540" allowFullScreen frameBorder="0"></iframe>

} while (reader.NextResult());

The first pass is on GitHub at and the resulting JSON looks like this:

"Status": "Live",
"Title": "Introduction to Azure Integration Service Environment for Logic Apps",
"Host": "Scott Hanselman",
"Guest": "Kevin Lam",
"Episode": 528,
"Live": "2019-02-26T00:00:00",
"Url": "",
"embedUrl": ""
"Status": "Live",
"Title": "An overview of Azure Integration Services",
"Host": "Lara Rubbelke",
"Guest": "Matthew Farmer",
"Episode": 527,
"Live": "2019-02-22T00:00:00",
"Url": "",
"embedUrl": ""

Thoughts? There's a dozen ways to have done this. How would you do this? Dump it into a DataSet and serialize objects to JSON, make an array and do the same, automate Excel itself (please don't do this), and on and on.

Certainly this would be easier if I could get a CSV file or something from the business person, but the issue is that I'm regularly getting new drops of this same sheet with new records added. Getting the suit to Save As | CSV reliably and regularly isn't sustainable.

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About Scott

Scott Hanselman is a former professor, former Chief Architect in finance, now speaker, consultant, father, diabetic, and Microsoft employee. He is a failed stand-up comic, a cornrower, and a book author.

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March 07, 2019 6:56
I have a similar need and I found the same nifty library. Will you be comparing the new JSON object with the existing one for all changes contained, or just appending new rows / episodes?

Can you share if you are storing the result in CosmosDB? (as it has been a recent topic on Azure Friday)

I enjoyed the post! Nice to consider new ways to do old tasks.

March 07, 2019 9:34
Is the Excel file in the old binary .xls format or is it the new xml based .xlsx?
March 07, 2019 12:42
I've a similar use case and use ExcelDataReader too.
But I'm using excelDataReader.AsDataSet with an ExcelDataSetConfiguration.
There is the ability to set ConfigureDataTable with UseHeaderRow = true.
March 07, 2019 21:35
I have used PowerShell for this kind of stuff for years. There is a module called ImportExcel that will let you do something like:

Import-Excel -Path myfile.xlsx | ConvertTo-Json

It works in PowerShell core, too!
March 07, 2019 22:06
Even though the question is 'how would you do this in C#' (or not?) I would probably do it with SheetJS in javascript - it has built in XLSX.utils.sheet_to_json() helper function and workin with JSON in javascript just feels more natural.
March 08, 2019 3:45
This video has a cool Blazor Excel sample - starting at about the 10 minute mark.
March 08, 2019 4:35
EPPlus is another fantastic excel library, you can even query your spreadsheet with linq. :) It's good for both reading and writing to your openxml-based spreadsheet. Good stuff.
March 08, 2019 13:53
var szFilePath = @"c:\temp\customers.xlsx";
var szConnectionString = string.Format("Provider=Microsoft.ACE.OLEDB.12.0;Data Source={0};Extended Properties=\"Excel 12.0 Xml;HDR=No;IMEX=1\";", szFilePath);

using (OleDbConnection conn = new OleDbConnection(szConnectionString))
OleDbDataAdapter objDA = new System.Data.OleDb.OleDbDataAdapter("select * from [Sheet1$]", conn);
DataTable dt = new DataTable();
var json = JsonConvert.SerializeObject(dt);
March 08, 2019 18:39
You can always use Channel 9's ODATA feed to get the show metadata, which for Azure Friday is'aeee37b6ab0a4c9f8779a2570148507b')/Entries
This should give you the latest 25 entries, then you go to'a97c1195-b987-487b-b590-a46800ac575e')/Entries?$skip=25 to get the next 25 and so on. And it is already in JSON format.

These feeds is what I use for creating download scripts at .For example, Azure Friday videos could be downloaded at
March 08, 2019 19:04
I'd probably start with Microsoft Flow
March 09, 2019 3:04
There is no other way I would do any work with Excel without EPPlus library (opensource).
March 10, 2019 22:03
If you use F# you can have strongly typed access using a type provider:
March 12, 2019 3:31
I like using the spreadsheet as an ODBC source such as MikeP commented.

This should allow you to filter by date or other attribute.

I also like accessing the document as an open office XML document.

March 12, 2019 5:00

I'm certainly not a developer, but wouldn't this PowerShell command work:

#Requires -Modules ImportExcel
Import-Excel -Path C:\temp\YourFile.xlsx -WorksheetName Sheet1 |
March 12, 2019 11:48
My advice is not to use excel datareaders from microsoft. Is it OLE DB or ADO or whatever.

It will bite you always because an update in the future of these underlying technologies will mess things up and brick your app. Try something with native access.

March 14, 2019 0:41
Using this ExcelDataReader, and AsDataSet, I'm not getting values out of cells containing formulas. It's not practical in real business life.
March 16, 2019 2:31
F# TypeProvider -> rows to F# Record of output schema -> records to JsonSerializer
March 16, 2019 23:34
Thanks for writing this amazing post. Also try to fastest Excel library.
March 19, 2019 16:38
The trick I just used was to export the data as CSV and make that an embedded resource in the DLL. A static constructor reads the data in and I'm ready to roll.

I'll have a look at the NuGet packet, maybe embedding the actual spreadsheet would be a better idea. What I have now is both the excel workbook for people to inspect and update and the CSV file for the build. If there's an update I have to "Save-As" to get the CSV data into source control / build.
March 20, 2019 6:02
I think I've used most of the approaches here at one time or another (including that OleDb one that if I recall right can get you into trouble if it gets the wrong type for the column, e.g. if your first thousand rows are integers and then it becomes alphanumeric I seem to remember it looking ahead, choosing int for the column and then borking far down the sheet when it hits alpha numeric values). Then you add more plumbing, then it works.

I like your approach though, your code is always straightforward. If it implements IDataReader I have ToJson and ToJsonStream extension methods I'd have used (Also have ToExcel, ToCsv, ToTab, To every other format I've ever needed and pack ratted away into my utility kit). Hehe.

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Disclaimer: The opinions expressed herein are my own personal opinions and do not represent my employer's view in any way.