Json Merge Patch Support for .Net 5

Json Merge Patch

• RFC 7396
• Backed by Newtonsoft.Json or System.Text.Json - your choice
• Supports conversion to JSON Patch, which can perform partial resource updates
• Supports Swagger
• .Net 5

Some inspiring projects:

• Here's a introduction to merge patch
• Morcatko's JsonMergePatch

C# Object	JSON	Resulting C# Object
var person = new Person() { FirstName = "John", LastName = "Doe" };	{ "LastName": "Smith" }	{ FirstName = "John", LastName = "Smith" }

// Apply all the changes in the patch to your existing DTO
[HttpPatch]
[Consumes(MergePatchDocument.ContentType)]
public IActionResult Patch([FromBody] IJsonMergePatch<Person> mergePatch)
{
    ...
    mergePatch.ToJsonPatch().ApplyTo(existingDTO);
    ...
}

//Acting on the presence/absence of a property in the patch
[HttpPatch]
[Consumes(MergePatchDocument.ContentType)]
public IActionResult Patch([FromBody] IJsonMergePatch<Person> mergePatch)
{
    if(mergePatch.TryGetValue(x => x.LastName, out var ln)
    {
        //act accordingly
    }
}

// If you need to create a patch document to call a different service
public void CreatePatch()
{
    //simple sets, one property at a time
    var mergePatch = JsonMergePatch.New();
    mergePatch.Set(x => x.LastName, "Smith");

    //or, use a builder, which can conditionally set values from other merge patchess
    var pb = JsonMergePatch.CreateBuilder<Person>();
    pb.Set(x => x.LastName).ToValue("Smith");
    var mergePatch = pb.Build();
}