jsonserializer

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# – Deserialize JSON to a dictionary

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I’ll show examples of how to deserialize JSON to dictionaries in different scenarios. Deserializing to Dictionary<string, string> When your JSON object has properties with simple string values (as opposed to nested objects), you can deserialize to Dictionary<string, string>. Here’s an example. Consider the following simple JSON object: Note: In all examples, I’ll show the pretty-printed … 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# – 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# – JSON value could not be converted to System.String

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When you send a request to ASP.NET with a JSON body, you get the following exception: System.Text.Json.JsonException: The JSON value could not be converted to System.String. Path: $ | LineNumber: 0 | BytePositionInLine: 1. You can’t deserialize JSON to a string. You’re either using a string parameter with [FromBody] or your model has a string … 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# – Manually validate objects that have model validation attributes

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You can use the Validator utility class to do manual attribute-based validation on any object, in any project type (as opposed to doing automatic model validation in ASP.NET). To do this, add model validation attributes to your class properties, then create an object and populate it (aka binding), and finally execute manual validation with the … Read more

C# – JSON deserializer returns null properties

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Let’s say you have the following JSON: When you go to deserialize it, you notice that all or some of its properties are null (or default for value types): This outputs the following (because person.Name is null and person.Pets is 0): The data is definitely there, so why did it set these properties to null … 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# – 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# – 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# – Deserialize a JSON array to a list

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When you’re working with a JSON array, you can deserialize it to a list like this: This deserializes all of the objects in the JSON array into a List<Movie>. You can use this list object like usual. Note: All examples will use System.Collections.Generic and System.Text.Json. I’ll exclude the using statements for brevity. Example – JSON … Read more

C# – Deserialize JSON as a stream

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Here’s an example of deserializing JSON from a file as a stream with System.Text.Json: Stream deserialization has three main benefits: In this article, I’ll go into details about these benefits and show a few other stream serialization scenarios. Benefits of deserializing as a stream Performance There are two ways to deserialize JSON: Deserializing a stream … 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