jsonserializer-serialize

C# – Copy a dictionary

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The simplest way to make a copy of a dictionary is to use the copy constructor. You pass the dictionary you want to copy to the new dictionary’s constructor, like this: Note: If you’re using a non-default comparer, you’ll want to pass it to the copy constructor (i.e. new Dictionary(d, d.Comparer)). The copy constructor handles … Read more

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# – 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# – 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# – Get the current date and time

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Use DateTime.Now to get the current date/time, like this: This outputs the system’s current date/time: Note: By default, it uses the current culture’s date format (from the OS). This is showing the US date format – MM/dd/yyyy. DateTime.Now is the local date/time from the system where the code is executing. Keep that in mind if … 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# – Use records as a shortcut for defining DTOs

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You can declare a record with a single line of code: Note: This feature was added in .NET 5 / C# 9. Records are basically classes (reference types) that work very well as simple data containers (i.e. DTOs). Here’s an example of using a record: This outputs the following: As shown, when you declare a … Read more

C# – Examples of using GroupBy() (Linq)

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Here’s an example of using the Linq GroupBy() method to group coders by language: This example outputs the following: GroupBy() produces groups that contain the grouping key (i.e. Language) and the list of objects in the group (i.e. the Coder objects). The GroupBy() syntax is complex because it supports many scenarios. You can select one … Read more

C# – How to use JsonExtensionData

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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

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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# – How to use JsonConverterAttribute

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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

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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# – How to match an anonymous type parameter in a mocked method

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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

Get SQL Server query results as JSON

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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

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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 – How to unit test your middleware class

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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

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

C# – Async/await with a Func delegate

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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

C# – Get all loaded assemblies

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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