Is it possible to ApplyTo() from a viewModel to a model?

First of all, thank you for this great package!

It seems that JsonPatchDocument<> expect an entity-model as a generic type in order to call the ApplyTo<> method to patch the entity-model.

This works great for the most part. However, I personally don't like to add validation rules to my entity-model. I rather add validation rules to a view-model/request-model. This way I have one entity-model representing the data being stored, and one entity-model per request representing incoming data from a request. The request-model would contain data annotation validation rules which are specific to the user's request.

Let's take the following code as example. In this example, I pass EntityModel to the JsonPatchDocument and the code works perfectly. However, in order for the request to work, you must pass EntityModel as a generic to the JsonPatchDocument<> method. However, the request must be validated before the data is persisted. This setup requires the user to add validation rules to the entity-model which will mean the same rules for every request!

[HttpPatch("{id:int}")]
public virtual async Task<IActionResult> Patch(int id, JsonPatchDocument<EntityModel> patchDoc)
{
    if(patchDoc == null || patchDoc.Operations == null || patchDoc.Operations.Count == 0)
    {
        return BadRequest(ModelState);
    }

    EntityModel model = await GetAsync(id);

    if (model == null)
    {
        return NotFound();
    }

    patchDoc.ApplyTo(model, ModelState); // this works with no problem since model is the same type as the generic given to JsonPatchDocument<>
    if (!ModelState.IsValid)
    {
        return new BadRequestObjectResult(ModelState);
    }

    // Perform the update on the model
    DisplayModel result = Mapper.Map<DisplayModel>(model);

    return Ok(result);
}

Since I like to keep the validation rules in a request-model, not in entity-model, it would be important to have an .ApplyTo() method that would accept an object (as source) not as the generic type found in the JsonPatchDocument<> and ModelState to track errors.

So the above example will look like this instead

[HttpPatch("{id:int}")]
public virtual async Task<IActionResult> Patch(int id, JsonPatchDocument<RequestModel> patchDoc)
{
    if(patchDoc == null || patchDoc.Operations == null || patchDoc.Operations.Count == 0)
    {
        return BadRequest(ModelState);
    }

    EntityModel model = await GetAsync(id);

    if (model == null)
    {
        return NotFound();
    }

    patchDoc.ApplyTo(model, ModelState); // This currently does not work, note here I am passing entity-model aka EntityModel and the generic in pathDoc is RequestModel !! important different types

    if (!ModelState.IsValid)
    {
        return new BadRequestObjectResult(ModelState);
    }

    // Perform the update on the model
    DisplayModel result = Mapper.Map<DisplayModel>(model);

    return Ok(result);
}

Will it be possible to add .ApplyTo<TType>(TType requestModel, ModelState) or is there a better approach for my request?

Here is an example if EntityModel

public class User
{
    public int Id { get; set; }

    public string Username { get; set; }

    public string FirstName { get; set; }

    public string MiddleName { get; set; }

    public string LastName { get; set; }

    public bool IsActive { get; set; }
}

Here is few examples of different request-models, in the above example PatchUser would be an example of RequestModel that I would pass to JsonPatchDocument<PatchUser>

public class PatchUser
{
    [MaxLength(50)]
    public string FirstName { get; set; }

    [MaxLength(50)]
    public string MiddleName { get; set; }

    [MaxLength(50)]
    public string LastName { get; set; }
}

public class CreateUser
{
    [Required, MinLength(5), MaxLength(50)]
    public string Username { get; set; }

    [Required, MaxLength(50)]
    public string FirstName { get; set; }

    [MaxLength(50)]
    public string MiddleName { get; set; }

    [MaxLength(50)]
    public string LastName { get; set; }
}

public class UpdateUser
{
    [Required, MaxLength(50)]
    public string FirstName { get; set; }

    [MaxLength(50)]
    public string MiddleName { get; set; }

    [MaxLength(50)]
    public string LastName { get; set; }
}

KevinDockx / JsonPatch

Is it possible to ApplyTo() from a viewModel to a model? #98