C# – Deserialize JSON as a stream

Here’s an example of deserializing JSON from a file as a stream with System.Text.Json: Stream deserialization has three main benefits: In this article, I’ll go into details about these benefits and show a few other stream serialization scenarios. Benefits of deserializing as a stream Performance There are two ways to deserialize JSON: Deserializing a stream … Read more

C# – How to use JsonExtensionData

Use the JsonExtensionData attribute (in System.Text.Json) to deserialize properties that aren’t part of the class. Without this, JSON fields that don’t match a property are simply ignored and the returned object will have null properties. Here’s an example of adding this attribute to a dictionary property: Now when you deserialize JSON to this Person class, … Read more

C# – Property order with System.Text.Json

You can use the JsonPropertyOrder attribute to control the order that properties get serialized. You specify the order as an integer, and it serializes the properties in ascending order. Here’s an example: Note: Properties have a default order value of 0. Now serialize an object to JSON: This generates the following JSON: Notice the properties … Read more

C# – How to use JsonConverterAttribute

You can use JsonConverterAttribute (from System.Text.Json) to apply a specific JsonConverter to a property. Apply this attribute on a property and specify the JsonConverter type to use, like this: In this example, it’s applying ExpirationDateConverter (a custom JSON converter) to handle the ExpirationDate. For reference, here’s ExpirationDateConverter’s definition: Now serialize the object to JSON: Here’s … Read more

C# – Changing the JSON serialization date format

When you serialize a date with System.Text.Json, it uses the standard ISO-8601 date format (ex: “2022-01-31T13:15:05.2151663-05:00”). Internally, it uses the built-in DateTimeConverter class for handling DateTime, which doesn’t give you a way to change the date format. To change the date format, you have to create a custom JSON converter and pass it in: This … Read more

C# – Convert an object to JSON

Converting an object to a JSON string is referred to as serialization. The best way to do serialization is by using a good JSON serializer. There are two primary options: I’ll show examples of both options below. Using JsonSerializer.Serialize() (in the built-in System.Text.Json) Here’s an example of using the built-in JsonSerializer.Serialize() (in System.Text.Json) to convert … Read more

C# – Map query results to multiple objects with Dapper

When you’re querying joined tables, you can map each row to multiple objects by using the multi mapping feature in Dapper. To multi map, you have to provide Dapper with the following: In this article, I’ll show examples of multi mapping. Note: If you don’t specify the split column, it’ll use the default of “Id”. … Read more

C# – How to programmatically update the User Secrets file

User Secrets are stored in secrets.json. This file is specific to your application. Once you know the path of secrets.json, you can load and update it. Here’s an example of how to update secrets.json programmatically: Note: 1) For brevity, this isn’t showing all using statements. 2) This is using Newtonsoft because it’s better than System.Text.Json … Read more

C# – Deserializing JSON with quoted numbers

There are two ways to represent numbers in JSON: as number literals (ex: 123) or as quoted numbers (ex: “123”). In this article, I’ll explain how quoted numbers are handled during deserialization in Newtonsoft and System.Text.Json and how to change the behavior. At the end, I’ll show how to write quoted numbers during serialization. Quoted … Read more

Get SQL Server query results as JSON

The simplest way to get query results as JSON is to use FOR JSON PATH in the query (note: this was added in SQL Server 2016): It returns the results as a single JSON string with one JSON object per row: Note: SQL Server returns the JSON without indenting. All examples in this article show … Read more

C# – How to update appsettings.json programmatically

You have to overwrite the appsettings.json file to be able to update values programmatically. You have to deal with the whole file, not individual parts of it. The process can be summarized in the following steps: There are two options for deserialization. You can either 1) Deserialize appsettings.json into a dynamic object or 2) Load … Read more

ASP.NET Core – Configure JSON serializer options

ASP.NET Core uses System.Text.Json as the default JSON serializer. To configure the JSON serializer options, call AddJsonOptions() in the initialization code: Calling AddJsonOptions() gives you access to the global JsonSerializerOptions object. This is used for all requests / responses. You can configure the options and add converters (including your own custom JSON converters). ASP.NET Core’s … Read more

How to use Newtonsoft in ASP.NET Core

By default, ASP.NET Core uses System.Text.Json for JSON serialization. If you want to use Newtonsoft instead: Note: Before .NET 6, do this in Startup.ConfigureServices(). Install the right package Microsoft packaged up Microsoft.AspNetCore.Mvc.NewtonsoftJson based on the framework version, so you can’t just install the latest package. You have to find the latest one for the framework … Read more

C# – Newtonsoft extension methods for HttpClient

System.Net.Http.Json provides extension methods that simplify getting and sending JSON with HttpClient. Internally, it uses System.Text.Json for serialization. What if you want to use Newtonsoft instead of System.Text.Json? You can use the following extension methods for that: These are modeled off of the extension methods in System.Net.Http.Json. HttpClient is used to fetch the JSON content … Read more

C# – Get and send JSON with HttpClient

The simplest way to get and send JSON with HttpClient is to use the GetFromJsonAsync() and PostAsJsonAsync() extension methods (in System.Net.Http.Json), like this: Note: You have to install the System.Net.Http.Json package if you’re using a framework version before .NET 5. These extension methods use System.Text.Json for serialization. They simplify things by abstracting away the common … Read more

C# – Serialize anonymous types with System.Text.Json

It’s common to need to customize serialization. When you need to do this, you’d typically need to create a custom JSON converter and pass it in during serialization. Depending on your scenario, an alternative approach is to use anonymous types, like this: Basically you select properties from another object and format them as desired, and … Read more

C# – How to use JsonConverterFactory

Let’s say you want to serialize the four datetime types – DateTime, DateTime?, DateTimeOffset, and DateTimeOffset? – in the same way. You want to serialize them to use the US date style (ex: 7/14/2021). There are two main ways to accomplish this: 1) Create a custom JsonConverter for each type or 2) Create a JsonConverterFactory … Read more

System.Text.Json – How to serialize non-public properties

By default, System.Text.Json.JsonSerializer only serializes public properties. If you want to serialize non-public properties, you have two options: In this article, I’ll show examples of both approaches for handling non-public properties. Updated 2022-02-22 to explain the new JsonInclude attribute added in .NET 5. Write a custom JSON converter to serialize non-public properties When the built-in … Read more

The JSON value could not be converted to System.DateTime

When you’re using System.Text.Json to deserialize a DateTime value, if the value isn’t in the format it expects, then it’ll throw a JsonException. It expects datetimes to be in the ISO-8601-1:2019 format (for example: 2021-07-12T12:35:34+00:00). For example, the following code is trying to deserialize a DateTime value in an unexpected format: This’ll throw the following … Read more

WinForms – How to prompt the user for a file

In a WinForms project, you can prompt the user to select a file by using the OpenFileDialog control: When you call ShowDialog(), it’ll prompt the user to select a file: When the user clicks Open, you’ll be able to get the file path they selected from the OpenFileDialog.FileName property. To use the OpenFileDialog control, drag … Read more

Deserializing JSON that contains an embedded JSON string

In this article, I’ll show an example of code that handles deserializing JSON that contains an embedded JSON string. I’ll refer to this as a JSON envelope. The reason to refer to this as an envelope is because it’s similar to how you send paper mail through the post office. You put a letter (the … Read more

C# – Create a custom JsonConverter for System.Text.Json

Most of the time System.Text.Json will get you want you want. You can pass in options to control JSON serialization and deserialization to a certain extent. But sometimes you’ll run into scenarios where you need to customize how it handles a specific type. This is where JsonConverter comes in. You can customize serialization / deserialization … Read more

JsonException: A possible object cycle was detected

When you use System.Text.Json.JsonSerializer to serialize an object that has a cycle, you get the following exception: System.Text.Json.JsonException: A possible object cycle was detected which is not supported. This can either be due to a cycle or if the object depth is larger than the maximum allowed depth of 0. In .NET 6+, you can … Read more

C# – Using SqlDataReader to process multiple result sets

In this article I’ll show how to use the SqlDataReader ADO.NET class in two scenarios involving multiple result sets: I have a StreamingService database that has Movies, Shows, and Episodes tables (linked to the shows). First I’ll show the model classes I’m mapping the data into. Then I’ll show the two scenarios where I’m using … Read more

C# – Serialize a tuple to JSON

When you serialize a tuple to JSON, it uses the the underlying ValueTuple’s field names – Item1 and Item2. It doesn’t matter if you’re using a named tuple, it won’t use the names you specified in the tuple declaration. This behavior is the same with Newtonsoft and System.Text.Json. Here’s an example of serializing a named … Read more