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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
When an anonymous type is defined in one assembly, it won’t match an anonymous type defined in another assembly. This causes problems when you’re unit testing and trying to mock a method that has an anonymous type parameter. For example, let’s say you’re trying to unit test the following method: To unit test this, you … Read more
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
When you’re using Moq to set up a mocked method, you can use Callback() to capture the parameters passed into the mocked method: There are two main use cases for capturing parameters in a test: In this article, I’ll show examples of using Callback() in those two scenarios, and then I’ll explain some problems to … Read more
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
There are three requirements for unit testing a middleware class: Here’s an example: This is a simple test that only checks the response status code. By passing in DefaultHttpContext, you have control over the request and response objects. You can set the request to whatever you need, and then verify the response. I’ll show examples … Read more
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
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
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
To make a Func delegate awaitable, you have to make its out parameter a Task, like this: This Func accepts an int parameter and returns a Task. Since it returns a Task, it can be awaited. Notice that this isn’t returning a value. Normally you’d use an Action delegate if you didn’t want to return … Read more
You can get all of the loaded assemblies with AppDomain.CurrentDomain.GetAssemblies(). Here’s an example of looping over all loaded assemblies and outputting their metadata: Note: This is outputting an interpolated string to the console. This outputs the following information: I’ll show more examples of how you can use the assembly information. Get custom assembly attributes Assembly … Read more
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
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
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
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
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
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
In this article I’ll explain how to copy an object. I’ll explain the difference between shallow and deep copying, and then show multiple ways to do both approaches for copying objects. At the end, I’ll show a performance and feature comparison to help you decide which object copying method to use. Shallow copy vs Deep … 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
Before .NET 5, the built-in JSON serializer (System.Text.Json) couldn’t handle serializing a dictionary unless it had a string key. Here’s an example running in .NET Core 3.1 to show the problem. This is initializing a dictionary with values and then attempting to serialize it. This results in exception: System.NotSupportedException: The collection type ‘System.Collections.Generic.Dictionary`2[System.Int32,System.String]’ is not … 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