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Elegant use of Patch in .NET: JsonPatch

Popularity：968 ℃/2025-02-06 09:06:08
introduction

In modern Web API development, we often need to partially update resources (Partial Update). TraditionalPUTThe request will require the entire object to be sent, andPATCHRequests can only send fields that need to be updated. Core providesJsonPatchDocument<T>To simplify this operation.

What is JsonPatch?

JsonPatch (based onRFC 6902) is a patch document in JSON format that allows the client to declaratively modify JSON resources. JsonPatch provides the following operations:

add: Add a new value

remove: Delete a field

replace: Replace the value of a field

move: Move a value

copy: Copy a value

test: Test whether a value meets expectations

Using JsonPatch in Core Web API

Installation dependence

JsonPatchBuilt in, you need to make sure your project references the package:

().AddNewtonsoftJson();
Create API Controller

Suppose we have oneProductkind:

public class Product
{
    public int Id { get; set; }
    public string Name { get; set; }
    public decimal Price { get; set; }
}

Then, createProductsControllerdeal withPATCHask:

[ApiController]
[Route("api/[controller]")]
public class ProductsController : ControllerBase
{
    private static List<Product> _products = new()
    {
        new Product { Id = 1, Name = "Laptop", Price = 1200 },
        new Product { Id = 2, Name = "Mouse", Price = 25 }
    };

    [HttpPatch("{id}")]
    public IActionResult Patch(int id, [FromBody] JsonPatchDocument<Product> patchDoc)
    {
        var product = _products.FirstOrDefault(p =>  == id);
        if (product == null)
        {
            return NotFound();
        }

        (product, ModelState);

        if (!)
        {
            return BadRequest(ModelState);
        }

        return Ok(product);
    }
}
Send a JsonPatch request

The client can send the followingPATCHask:

[
    { "op": "replace", "path": "/price", "value": 999.99 }
]

Example cURL request:

curl -X PATCH "http://localhost:5000/api/products/1" \
     -H "Content-Type: application/json" \
     -d '[{"op": "replace", "path": "/price", "value": 999.99}]'

Handle possible problems with JsonPatch

Make sure the JSON format is correct

JsonPatch syntax is prone to errors, such as incorrect or missing path formatop. It is recommended to use Postman or cURL for debugging.

Handling ModelState errors

if(product, ModelState);Returns an error, should returnBadRequest(ModelState)and provide detailed error information.

in conclusion

JsonPatchProvides an elegant way to partial updates avoidingPUTRedundancy of the entire object is required. Reasonable useJsonPatch, can improve the flexibility and efficiency of the API.

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