ASP.NET Core in .NET 10 Preview 4: JSON Patch with System.Text.Json

With .NET 10 Preview 4 onwards, you can now use JsonPatch with System.Text.Json in ASP.NET Web API. 

Currently if you need to use JsonPatch you need to rely on Newtonsoft.Json as described in this article: JsonPatch in ASP.NET Core web API

Note: this isn't a complete drop-in replacement for the existing Newtonsoft.Json based implementation. In particular, the new implementation doesn't support dynamic types (like ExpandoObject).

Now let's see how this works.

First you need to install a new package, Microsoft.AspNetCore.JsonPatch.SystemTextJson. Note: it's still prerelease.

dotnet add package Microsoft.AspNetCore.JsonPatch.SystemTextJson --prerelease

Next, we can use the JsonPatchDocument<TModel>, that is introduced in Microsoft.AspNetCore.JsonPatch.SystemTextJson.

using Microsoft.AspNetCore.JsonPatch.SystemTextJson;
using Microsoft.AspNetCore.Mvc;
 
namespace WebApplication1.Controllers;
 
[ApiController]
[Route("[controller]")]
public class EmployeesController : ControllerBase
{
    [HttpPatch]
    [Route("{employeeId}")]
    public Employee PatchEmployee([FromRoute] int employeeId, 
        JsonPatchDocument<Employee> patchDocument)
    {
        Employee employee = new()
        {
            Id = employeeId,
            FirstName = "John",
            LastName = "Doe",
            Address = new Employee.AddressDto
            {
                Street = "123 Main St",
                City = "Redmond",
                State = "WA",
                ZipCode = "12345"
            }
        };
        patchDocument.ApplyTo(employee);
 
        return employee;
    }
}

You don't have to do any changes to the Program.cs.

WebApplicationBuilder builder = WebApplication.CreateBuilder(args);
 
builder.Services.AddControllers();
 
WebApplication app = builder.Build();
  
app.MapControllers();
 
app.Run();

And invoke the endpoint like follows.

@WebApplication1_HostAddress = https://localhost:7070
 
PATCH {{WebApplication1_HostAddress}}/employees/1
Content-Type: application/json
 
[
    {
        "op": "replace",
        "path": "/LastName",
        "value": "Bloggs"
    },
    {
        "op": "replace",
        "path": "/Address/ZipCode",
        "value": "90100"
    }
]

PATCH

Hope this helps.

Happy Coding.

Regards,

Jaliya