https://nuget.org/packages/MethodDecorator.Fody/
PM> Install-Package MethodDecorator.Fody
This is an add-in for Fody
Compile time decorator pattern via IL rewriting
This version is fork of Fody/MethodDecorator with changes I found useful
Differences from original Fody/MethodDecorator:
- No attributes or interfaces in root namespace (actually without namespace) are required
- Interceptor attribute can be declared and implemented in a separate assembly
- Init method is called before any method and receives the method reference and args
- OnEntry/OnExit/OnException methods don't receive the method reference anymore
- IntersectMethodsMarkedByAttribute attribute allows you to intersect a method marked by any attribute
// Atribute should be "registered" by adding as module or assembly custom attribute
[module: Interceptor]
// Any attribute which provides OnEntry/OnExit/OnException with proper args
[AttributeUsage(AttributeTargets.Method | AttributeTargets.Constructor | AttributeTargets.Assembly | AttributeTargets.Module)]
public class InterceptorAttribute : Attribute, IMethodDecorator {
// instance, method and args can be captured here and stored in attribute instance fields
// for future usage in OnEntry/OnExit/OnException
public void Init(object instance, MethodBase method, object[] args) {
TestMessages.Record(string.Format("Init: {0} [{1}]", method.DeclaringType.FullName + "." + method.Name, args.Length));
}
public void OnEntry() {
TestMessages.Record("OnEntry");
}
public void OnExit() {
TestMessages.Record("OnExit");
}
public void OnException(Exception exception) {
TestMessages.Record(string.Format("OnException: {0}: {1}", exception.GetType(), exception.Message));
}
}
public class Sample {
[Interceptor]
public void Method()
{
Debug.WriteLine("Your Code");
}
}
public class Sample {
public void Method(int value) {
InterceptorAttribute attribute =
(InterceptorAttribute) Activator.CreateInstance(typeof(InterceptorAttribute));
// in c# __methodref and __typeref don't exist, but you can create such IL
MethodBase method = MethodBase.GetMethodFromHandle(__methodref (Sample.Method),
__typeref (Sample));
object[] args = new object[1] { (object) value };
attribute.Init((object)this, method, args);
attribute.OnEntry();
try {
Debug.WriteLine("Your Code");
attribute.OnExit();
}
catch (Exception exception) {
attribute.OnException(exception);
throw;
}
}
}
NOTE: this is replaced by null when the decorated method is static or a constructor.
This is supposed to be used as
// all MSTest methods will be intersected by the code from IntersectMethodsMarkedBy
[module:IntersectMethodsMarkedBy(typeof(TestMethod))]
You can pass as many marker attributes to IntersectMethodsMarkedBy as you want
[module:IntersectMethodsMarkedBy(typeof(TestMethod), typeof(Fact), typeof(Obsolete))]
Example of IntersectMethodsMarkedByAttribute implementation
[AttributeUsage(AttributeTargets.Module | AttributeTargets.Assembly)]
public class IntersectMethodsMarkedByAttribute : Attribute {
// Required
public IntersectMethodsMarkedByAttribute() {}
public IntersectMethodsMarkedByAttribute(params Type[] types) {
if (types.All(x => typeof(Attribute).IsAssignableFrom(x))) {
throw new Exception("Meaningfull configuration exception");
}
}
public void Init(object instance, MethodBase method, object[] args) {}
public void OnEntry() {}
public void OnExit() {}
public void OnException(Exception exception) {}
}
Now all your code marked by [TestMethodAttribute] will be intersected by IntersectMethodsMarkedByAttribute methods. You can have multiple IntersectMethodsMarkedByAttributes applied if you want (don't have idea why). MethodDecorator searches IntersectMethodsMarkedByAttribute by predicate StartsWith("IntersectMethodsMarkedByAttribute")
- Make Init method optional
- Add "this" as parameter to Init method if method is not static
- Pass return value to "OnExit" if method returns any
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