Asp.netMVCPatchExample

Update

Different people have ran with this idea, one of them is: [https://github.com/viklele/DeltaPatcher] I would definitely recommend checking this out as well.

Example

An example of how to implement a patch method, similar to the Patch from Delta of oData...

I found it incredibly annoying that oDatas patch was case sensitive, thus i decided to do away with the whole oData part, since it is a huge library that we are abusing....

I decided to implement my own patch method, since that is the muscle that we are actually lacking. I created the following abstract class:

    public abstract class AbstractModel
    {
        public void Patch(Object u)
        {
            var props = from p in this.GetType().GetProperties()
                        let attr = p.GetCustomAttribute(typeof(NotPatchableAttribute))
                        where attr == null
                        select p;
            foreach (var prop in props)
            {
                var val = prop.GetValue(this, null);
                if (val != null)
                    prop.SetValue(u, val);
            }
        }
    }

Then i make all my model classes inherit from *AbstractModel*. note the line where i use *let*, i will excplain that later. So now you can remove the Delta from you controller action, and just make it Entry again, as with the put method. e.g.

    public IHttpActionResult PatchUser(int id, Entry newEntry)

You can still use the patch method the way you used to:

    var entry = dbContext.Entries.SingleOrDefault(p => p.ID == id);
    newEntry.Patch(entry);
    dbContext.SaveChanges();

Now, let's get back to the line

    let attr = p.GetCustomAttribute(typeof(NotPatchableAttribute))

I found it a security risk that just any property would be able to be updated with a patch request. For example, you might now want the an ID to be changeble by the patch. I created a custom attribute to decorate my properties with. the NotPatchable attribute:

    public class NotPatchableAttribute : Attribute {}

You can use it just like any other attribute:

    public class User : AbstractModel
    {
        [NotPatchable]
        public int ID { get; set; }
        [NotPatchable]
        public bool Deleted { get; set; }
        public string FirstName { get; set; }
    }

This in this call the Deleted and ID properties cannot be changed though the patch method.

I hope this solve it for you as well. Do not hesitate to leave a comment if you have any questions.

I added a screenshot of me inspecting the props in a new mvc 5 project. As you can see the Result view is populated with the Title and ShortDescription.

![Example of inspecting the props][1]