Correctly Serialize and Deserialize DateTime in .NET Web API and Blazor

Learn how to properly handle DateTime serialization and deserialization between .NET Web API and Blazor, ensuring correct data representation and seamless integration.
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Introduction

Working with dates and times in web applications can sometimes lead to unexpected challenges, especially when dealing with serialization and deserialization. If you’re a developer using .NET Web API and Blazor, you might have faced difficulties when trying to retrieve and display server times in your Blazor app. Your code might seem perfect, yet you stumble upon issues that lead to incorrect DateTime values being displayed. Let’s explore a common scenario you might encounter.

The Problem

You have implemented a Web API endpoint that returns the current server time, but when you try fetching this data in your Blazor app, the DateTime seems to return the default value: 1/1/0001 12:00:00 AM. This unexpected response points to potential issues with how your data is serialized and deserialized.

Understanding the Scenario

Here’s a brief look at your current setup:

Controller Code

You have a controller that returns the server's local time wrapped in a DTO:

[[See Video to Reveal this Text or Code Snippet]]

DTO Class

Your DtoValue class is defined as follows:

[[See Video to Reveal this Text or Code Snippet]]

Web API Serialization

You’ve also configured your Web API to use Newtonsoft.Json for serialization:

[[See Video to Reveal this Text or Code Snippet]]

Then you retrieve the data in your Blazor app like so:

[[See Video to Reveal this Text or Code Snippet]]

Unfortunately, this attempts to deserialize the DateTime incorrectly, resulting in unexpected outputs.

Solutions to the Problem

1. Understanding Serialization Differences

One primary reason for this issue is the difference in the default JSON serialization behavior between Newtonsoft.Json and System.Text.Json (the default JSON serializer in .NET Core). The DtoValue class utilizes a field for the Value property, but by default, the System.Text.Json serializer does not serialize fields.

Fix: Use Properties Instead of Fields

To correct this, modify the DtoValue class to use a property for Value:

[[See Video to Reveal this Text or Code Snippet]]

2. Update the Blazor Client

You might have added Newtonsoft.Json only on the server-side, which is unnecessary since Blazor by default uses the built-in System.Text.Json. Ensure your DTO complies with this serializer's expectations.

3. Recommended Change: Use DateTimeOffset

Consider changing your type from DateTime to DateTimeOffset. This will give you better handling of time zones and daylight saving time, which is important for web applications that may operate across various time zones.

Example Update

Here’s how your updated code would look:

DTO Class:

[[See Video to Reveal this Text or Code Snippet]]

Controller Code:

[[See Video to Reveal this Text or Code Snippet]]

Blazor Fetch Call:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By making these adjustments, you should be able to correctly serialize and deserialize the DateTime or DateTimeOffset values, ensuring that your Blazor application accurately displays the server time. Remember, using properties instead of fields for data serialization is essential for compatibility with the default JSON serialization configurations in .NET. Happy coding!