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Articles about doing JSON (de)serialization with C# using .NET (with examples using System.Text.Json and Newtonsoft).
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
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. You can pass in a JsonSerializerSettings object to … Read more
The simplest way to get and send JSON with HttpClient is to use the GetFromJsonAsync() and PostAsJsonAsync() extension methods found in System.Net.Http.Json, like this: Note: You have to install the System.Net.Http.Json nuget 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 … Read more
It’s common to need to customize serialization. When you need to do this, you’d typically need to create a custom 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 then … Read more
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: Here’s how to do the JsonConverterFactory approach to solve this problem: To use … Read more
By default, System.Text.Json.JsonSerializer only serializes public properties. If you want to serialize non-public properties, you have two options: Create a custom converter and use reflection to get the non-public properties. Use the JsonInclude attribute to enable (de)serialization of public properties with non-public accessors (not the same as non-public properties). In this article, I’ll show examples … Read more
When deserializing a datetime value with System.Text.Json.JsonSerializer, 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 exception: System.Text.Json.JsonException: … Read more
When you send mail, you put a letter in an envelope and put routing information on the envelope. The postal service uses the routing information to deliver the envelope to a specific mailbox. The mailbox owner then opens the envelope and reads the letter. Sometimes you may need to deal with the JSON equivalent of … Read more
Most of the time System.Text.Json will get you want you want. You can pass in options to control 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 for … Read more
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
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
Problem When using System.Text.Json, it’s a good idea to reuse JsonSerializerOptions objects. This leads to a massive 200x speedup in subsequent calls to the serializer. The downside is you can’t change properties on the options object after you’ve passed it in a Serialize()/Deserialize() call. You’ll get the exception: System.InvalidOperationException: Serializer options cannot be changed once … Read more
The appsettings.json file is a convenient way to store and retrieve your application’s configuration. You can add it to any project and then use the Microsoft.Extensions.Configuration library to work with it. Since appsettings.json is just a JSON file, you can add any section / values you want (this is easier than working with XML-based app.config … Read more
Reusing JsonSerializerOptions (from System.Text.Json) is optimal for performance. It caches type info, which results in a 200x speedup when it deals with the type again. Therefore, always try to reuse JsonSerializerOptions. I’ll show a speed comparison of serializing with and without reusing JsonSerializerOptions. Measuring the performance gains of reusing JsonSerializerOptions To measure the performance gains … Read more
Problem When you try to serialize an object using Newtonsoft.Json and there’s a circular reference, you get the following exception: Newtonsoft.Json.JsonSerializationException: Self referencing loop detected for property Here’s an example of code that results in this exception: The Parent object references the Child object, which references the Parent object. Hence, a circular reference (aka a … Read more
When you’re using System.Text.Json to deserialize JSON that contains the string representation of an enum, you get the following exception: System.Text.Json.JsonException: The JSON value could not be converted to <Enum Type> The following JSON would cause this exception. Conference is an enum, and this is using the string representation “NFC” instead of the numeric value … Read more
By default Newtonsoft does case insensitive JSON deserialization and System.Text.Json does case sensitive JSON deserialization. Case sensitivity comes into play when a JSON string is being deserialized into an object. If you’re using case sensitive deserialization, then keys in the JSON string must match type names exactly, otherwise it won’t deserialize the class/property with the … Read more
The built-in JSON serializer in .NET Core can’t handle serializing a dictionary unless it has a string key. When I run this code I get the following exception: System.NotSupportedException: The collection type ‘System.Collections.Generic.Dictionary`2[System.Int32,System.String]’ is not supported. It can only serialize dictionaries with string keys. This is bizarre, and another reason to stick with Newtonsoft for … Read more
If you’re switching from Newtonsoft.Json to System.Text.Json (or vice versa), you may be wondering how to specify the common options you’re used to using in Newtonsoft. For example, how do you specify the equivalent of Newtonsoft.Json.Converters.StringEnumConverter in System.Text.Json? The following table shows a few common serialization options used in Newtonsoft.Json and their equivalents in System.Text.Json. … Read more
If you want to deserialize JSON without having to create a bunch of classes, your best option is to use Newtonsoft.Json. Here’s an example. Let’s say you want to deserialize the following JSON: To deserialize this to a dynamic object with Newtonsoft, use JsonConvert.DeserializeObject<dynamic>: This outputs the following: Deserialize to ExpandoObject in older versions of … Read more
