jsonserializeroptions

C# – Serialize a dictionary to JSON

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When you want to convert a dictionary to a JSON string, you can use the built-in JsonSerializer (from System.Text.Json) to serialize the dictionary. Here’s an example: Note: This is passing in WriteIndented=true to pretty print the JSON string for readability. This serializes the dictionary to a JSON string with the following format: I’ll show more … Read more

C# – Convert JSON to an object

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Converting a JSON string to an object is referred to as deserialization. You can do this with a JSON serializer. There are two primary options: I’ll show examples by deserializing the following Movie JSON to a Movie object: Movie JSON: Movie class (properties match JSON): Using JsonSerializer.Deserialize() (in System.Text.Json) To deserialize with the built-in JsonSerializer.Deserialize(), … Read more

C# – Serialize to JSON in alphabetical order

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There are two ways to serialize an object’s properties to JSON in alphabetical order using System.Text.Json: I’ll show how to do these two options below. Option 1 – Manually alphabetize with JsonPropertyOrder You can specify the exact serialization ordering by using the JsonPropertyOrder attribute. Therefore, to serialize in alphabetical order, first arrange the properties in … Read more

C# – Serialize and deserialize a multidimensional array to JSON

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System.Text.Json doesn’t support serializing / deserializing multidimensional arrays. When you try, it throws an exception like this – System.NotSupportedException: The type ‘System.Int[,] is not supported. You have three options: In this article, I’ll show an example of how to create a custom JsonConverter that handles multidimensional arrays. In this example, I’ll specifically show how to … Read more

C# – How to update a file’s contents

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There are three ways to update a file’s content: Which option you pick depends on the file’s format and size. For example, if you’re writing to an existing CSV file, you’d append new lines to the end of the file. If you’re updating a JSON file, you’d read all the JSON content, make changes, then … Read more

C# – How to send synchronous requests with HttpClient

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In .NET 5 and above, you can use the HttpClient Sync API methods – Send() and ReadAsStream() – to send HTTP requests synchronously (as opposed to resorting to sync-over-async). Here’s the steps for doing this: HttpClient was originally designed for async requests and has many async convenience methods (like GetAsync() and ReadAsStringAsync()). There aren’t sync … Read more

C# – Ignore null properties during JSON serialization

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By default, null properties are included during JSON serialization like this: There are two ways to ignore null properties: In this article, I’ll show examples of these two ways to ignore null properties. I’ll show how to do it with System.Text.Json and Newtonsoft. Ignore null properties with System.Text.Json Use JsonIgnoreCondition.WhenWritingNull to ignore null properties. You … Read more

C# – How to use JsonNode to read, write, and modify JSON

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When you don’t want to create classes for JSON (de)serialization, one option is to use JsonNode. This allows you work with JSON as a mutable DOM that consists of JsonNode objects (JsonObject, JsonArray, JsonValue). You can use it to read, write, and modify JSON. Here’s an example. Let’s say you have the following JSON that … Read more

C# – How to read problem details JSON with HttpClient

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Problem details (RFC7807) is a standardized error response format that has a Content-Type of application/problem+json, an error response code (i.e. 400 – Bad Request), and has a response body that looks like this: This can be extended to include any number of properties. The example shown above comes from the default way ASP.NET Core returns … Read more

C# – JSON object contains a trailing comma at the end which is not supported

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Problem When you deserialize JSON with a “trailing comma”, you get the following error: The JSON object contains a trailing comma at the end which is not supported in this mode. Change the reader options. JSON properties are separated with commas. A trailing comma is one that has no properties after it. Here’s an example … Read more

C# – Deserialize JSON using different property names

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When JSON property names and class property names are different, and you can’t just change the names to match, you have three options: These options affect both deserialization and serialization. Let’s say you have the following JSON with camel-cased property names: Here’s an example of using the JsonPropertyName attribute: Note: The Newtonsoft equivalent is [JsonProperty(“title”)] … Read more

C# – Deserialize JSON with a specific constructor

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When your class has multiple constructors, you can use the JsonConstructor attribute to specify which constructor to use during deserialization. Here’s an example. The Person class has two constructors. I put the JsonConstructor attribute on one of the constructors: Note: JsonConstructor for System.Text.Json was added in .NET 5. Now deserialize a JSON string to the … Read more

C# – Deserialize JSON to a derived type

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The simplest way to deserialize JSON to a derived type is to put the type name in the JSON string. Then during deserialization, match the type name property against a set of known derived types and deserialize to the target type. System.Text.Json doesn’t have this functionality out of the box. That’s because there’s a known … Read more

C# – Populate an existing object with JSON

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Normally when you’re working with JSON, you deserialize it to a target type and get back an initialized and fully populated object. How about if you need to initialize an object yourself, and then populate it with JSON later? For example, let’s say you want to load the following JSON array into a case-insensitive HashSet: … Read more

C# – Property order with System.Text.Json

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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# – Changing the JSON serialization date format

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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

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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# – Deserializing JSON with quoted numbers

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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

C# – How to update appsettings.json programmatically

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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

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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

C# – Get and send JSON with HttpClient

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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

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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

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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

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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

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

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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