Pygmalions.Prism.Decorating 1.0.2

Prism Decorating

This plugin provides a mechanism to modify the behavior of functions in run-time.

How to Use

By simply mark [Decorate] attribute on any non-final virtual method of a class, this plugin will implement the IDecorated interface in the proxy class. Method decorators can be get through GetMethodDecorator(MethodInfo) method provided by IDecorated interface.

For example, this is the code of a sample class:

public class SampleObject
{
    [Decorate]
    public virtual int Value { get => BackingValue; set => BackingValue = value; }

    public int BackingValue = 0;

    [Decorate]
    public virtual int Add(int value) => BackingValue + value;
    
    public SampleObject()
    {}

    public SampleObject(int initialValue)
    {
        BackingValue = initialValue;
    }
}

Firstly, initialize a proxy generator and load this plugin:

// Initialize a proxy generator.
var generator = new Generator();
// Load decoration plugin.
generator.RegisterPlugin(new DecorationPlugin());

Secondly, create a instance of the proxy class:

var instance = Activator.CreateInstance(generator.GetProxy<SampleObject>());

Convert this instance into the original type and the IDecorated interface separately:

var proxy = (IDecorated)instance!;
var sample = (SampleObject)instance!;

Get the decorator of Add(int) method. In this example, the code in that method will be skipped, and the return value will be set to 10.

var decorator = 
    proxy.GetMethodDecorator(typeof(SampleObject).GetMethod(nameof(SampleObject.Add))!);

decorator!.Invoking += (ref Invocation invocation) =>
{
    invocation.Result = 10;
    invocation.Skipped = true;
};

Invoke the decorated method, the result here will be 10, no matter what the argument is given.

var result = sample.Add(3);