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 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

System.Text.Json – Using anonymous types to customize serialization

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

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: 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

System.Text.Json.JsonException: The JSON value could not be converted to System.DateTime

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

Deserializing JSON that contains an embedded JSON string

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

System.Text.Json.JsonException: A possible object cycle was detected which is not supported

When you use System.Text.Json.JsonSerializer to serialize an object that has a cycle, you’ll 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. This is the same problem … Read more

System.InvalidOperationException: Serializer options cannot be changed once serialization or deserialization has occurred

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

ASP.NET – How to add User Secrets

To add User Secrets in an ASP.NET project in Visual Studio do the following steps: Right-click the project and click Manage User Secrets. This will create and open a file called secrets.json. Override appsettings.json settings by putting them in secrets.json For example, let’s say your appsettings.json looks like this: You want to override ApiKey. In … Read more

C# – How to read custom configurations from appsettings.json

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 anything to it (as long as it’s valid JSON). Compared with working with the … Read more

.NET JsonSerializer is over 200x faster if you reuse JsonSerializerOptions

When you serialize an object using the built-in .NET JsonSerializer (System.Text.Json), reusing the JsonSerializerOptions object is 200x faster than serializing with a new options object each time. The JsonSerializerOptions object must have some kind of internal caching mechanism that makes subsequent serializations on the same type significantly faster. Note: Creating the new JsonSerializerOptions object adds … Read more

Newtonsoft.Json.JsonSerializationException: Self referencing loop detected for property

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 For example, I have a Parent class and Child class. The Parent object has a reference to a Child object, which has a back reference to the Parent … Read more

JsonException: The JSON value could not be converted to Enum

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

C# – Case sensitivity in JSON deserialization

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

System.Text.Json can’t serialize Dictionary unless it has a string key

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

Common Newtonsoft.Json options in System.Text.Json

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

C# – Deserialize JSON to dynamic object

If you want to deserialize JSON without having to create a bunch of classes, use Newtonsoft.Json like this: Now you can use this object like any other object. Example Add the Newtonsoft.Json reference Code Output: JSON Dynamic vs ExpandoObject If you specify <dynamic> instead of <ExpandoObject> it’ll create a JObject. In older versions of Newtonsoft, … Read more