JsonMergePatch

Json Merge Patch RFC 7396 for .NET

Packages	Version
Adv76.JsonMergePatch
Adv76.AspNetCore.JsonMergePatch

Usage

Basic

Suppose you have Class1 below:

public class Class1
{
    public int Int0 { get; set; }
    public string? String0 { get; set; }
    public double Double0 { get; set; }
}

And suppose you have this instance:

var obj = new Class1()
{
    Int0 = 1,
    String0 = "Hello World",
    Double0 = 3.5,
};

A simple example of patching this object:

var result = JsonMergePatcher.SafeApplyTo(ref obj, """
{
    "Int0": 42,
    "String0": "Sphinx of black quartz, judge my vow."
}
""");

If the patch succeeded, result.Succeeded will equal true and obj will have the "Int0" and "String0" properties updated to the corresponding values.

ASP.NET Core

For ASP.NET Core, there are a few additional helpers.

First an example of a basic patch endpoint (Minimal API):

app.MapPatch("/class1", Results<Ok<Class1>, ValidationProblem>(JsonMergePatchDocument<Class1> doc) =>
{
    var result = doc.SafeApplyTo(ref class1);
    if (result.Succeeded)
    {
        return TypedResults.Ok(class1);
    }

    return TypedResults.ValidationProblem(result);
})

A couple of things to note from the snippet above:

1. JsonMergePatchDocument<T> is a wrapper class that automatically populates the patch document from the HTTP Request body. Calling SafeApplyTo() on the patch document internally calls the JsonMergePatcher.SafeApplyTo() method.
2. TypedResults is extended with an additional overload for TypedResults.ValidationProblem() that accepts a JsonMergePatchResult for returning errors to the user.

OpenAPI Integration

Generate strongly-typed OpenAPI documents with the OpenAPI integration. By default, the OpenAPI document just shows an empty object for the body of patch endpoints.

Register the transformer when configuring OpenAPI:

using Adv76.AspNetCore.JsonMergePatch.OpenApi;

...

builder.Services.AddOpenApi(options => options.AddJsonMergePatch());

Endpoints with body type of JsonMergePatchDocument<T> get a merge-patch request body schema in the OpenAPI document.

• All properties are optional and nullable.
• Properties block from patching via security policies are hidden.
• Nested objects recurse into their own patch schemas.