DecorateWithInterceptor

Example

Given definitions for the following in an assembly:

NOTE: The following example expects that an IConsole implementation is registered in the IServiceCollection See LSL.AbstractConsole for an implementation that can be used with an IServiceCollection via the LSL.AbstractConsole.ServiceProvider package.

public interface ISyncServiceToDecorate
{
    void DoSomething();
}

public class SyncServiceToDecorate : ISyncServiceToDecorate
{
    private readonly IConsole _console;

    public SyncServiceToDecorate(IConsole console) => _console = console;

    public void DoSomething() => _console.WriteLine("Something done");
}

public class MyInterceptor : IInterceptor
{
    private readonly IConsole _console;

    public MyInterceptor(IConsole console) => _console = console;

    public void Intercept(IInvocation invocation)
    {
        _console.WriteLine($"Before invoke of {invocation.Method.Name}");
        invocation.Proceed();
        _console.WriteLine($"After invoke of {invocation.Method.Name}");
    }
}

Then we can easily register a decorator with the provided interceptor as follows:

services
    .AddInterceptorsFromAssemblyOf<MyInterceptor>()
    .AddAbstractConsole()
    .AddScoped<ISyncServiceToDecorate, SyncServiceToDecorate>()
    .DecorateWithInterceptor<ISyncServiceToDecorate, MyInterceptor>();

Now we can just inject an ISyncServiceToDecorate and get MyInterceptor to intercept every call on it.

If using the aforementioned IConsole implementation, then a class that consumes ISyncServiceToDecorate as shown below would get intercepted:

public class MyConsumer
{
    private readonly ISyncServiceToDecorate _syncServiceToDecorate;

    public MyConsumer(ISyncServiceToDecorate syncServiceToDecorate) => 
        _syncServiceToDecorate = syncServiceToDecorate;

    public void DoSomethingElse()
    {
        // This would result in an `IConsole`
        // getting output of:
        // Before invoke of 'DoSomething'
        // Something done
        // After invoke of 'DoSomething'
        _syncServiceToDecorate.DoSomething();
    }
}

Example with multiple interceptors

Using the classes in the previous example we can add a new interceptor to show registration of multiple interceptors using a configuration delegate:

// Extra interceptor
public class MyOtherInterceptor : IInterceptor
{
    private readonly IConsole _console;

    public MyInterceptor(IConsole console) => _console = console;

    public void Intercept(IInvocation invocation)
    {
        _console.WriteLine($"(Other) Before invoke of {invocation.Method.Name}");
        invocation.Proceed();
        _console.WriteLine($"(Other) After invoke of {invocation.Method.Name}");
    }
}

The following code will then register both interceptors against our service:

services
    .AddInterceptorsFromAssemblyOf<MyInterceptor>()
    .AddAbstractConsole()
    .AddScoped<ISyncServiceToDecorate, SyncServiceToDecorate>()
    .DecorateWithInterceptor<ISyncServiceToDecorate>(c => c
        .AddInterceptor<MyInterceptor>()
        .AddInterceptor<MyOtherInterceptor>());

Now the following consumer code will result in extra logging:

public class MyConsumer
{
    private readonly ISyncServiceToDecorate _syncServiceToDecorate;

    public MyConsumer(ISyncServiceToDecorate syncServiceToDecorate) => _syncServiceToDecorate = syncServiceToDecorate;

    public void DoSomethingElse()
    {
        // This would result in an `IConsole`
        // getting output of:
        // (Other) Before invoke of 'DoSomething'
        // Before invoke of 'DoSomething'
        // Something done
        // After invoke of 'DoSomething'
        // (Other) After invoke of 'DoSomething'
        _syncServiceToDecorate.DoSomething();
    }
}