Pass parameters to the constructor in Method Decorator Fody

Question

This is my code of the Attribute Class that extends IMethodDecorator Interface

[AttributeUsage(AttributeTargets.Method | AttributeTargets.Constructor | AttributeTargets.Assembly | AttributeTargets.Module | AttributeTargets.Field)]
public class LogAttribute : Attribute, IMethodDecorator
{
    ILogger log = Logger.Factory.GetLogger<Logger>();
    String methodName;


    public LogAttribute() {
    }

    public void Init(object instance, MethodBase method, object[] args)
    {
        methodName = method.Name;
    }

    public void OnEntry()
    {
        Console.WriteLine(methodName);
        log.Debug(methodName);
    }

    public void OnExit()
    {
        Console.WriteLine("Exiting Method");
    }

    public void OnException(Exception exception)
    {
        Console.WriteLine("Exception was thrown");
    }

}

I want to be able to use this as

[log("some logmessage")]
void method() 
{
// some code  
}

Any ideas ? I am using Method Decorator Fody package.

Attributes in .NET allows parameter contructor; have you tried `public LogAttribute(string logMessage) { }`? — jlvaquero, May 30 '16 at 11:49
MethodDecorator Fody does not work with parameterized constructor. — Vasudha Gupta, Jun 01 '16 at 08:30
@VasudhaGupta Yes it does. You need to provide an overloaded constructor - one accepting no parameters for the module attribute and one with the parameters that you'd like to pass when you decorate your method. — a11smiles, Jul 18 '19 at 03:44

score 3 · Accepted Answer · answered Jun 01 '16 at 08:31

So I found a solution to my problem.

Basically I modified my class like -

[AttributeUsage(AttributeTargets.Method | AttributeTargets.Constructor | AttributeTargets.Assembly | AttributeTargets.Module | AttributeTargets.Field)]
public class LogAttribute : Attribute, IMethodDecorator
{
    ILogger log = Logger.Factory.GetLogger<Logger>();
    String methodName;

    public String logMessage { get; set; }

    private Lazy<IEnumerable<PropertyInfo>> _properties;
    public MethodBase DecoratedMethod { get; private set; }

    public LogAttribute() {
        this._properties = new Lazy<IEnumerable<PropertyInfo>>(() =>
         this.GetType()
             .GetRuntimeProperties()
             .Where(p => p.CanRead && p.CanWrite));
    }


    public void Init(object instance, MethodBase method, object[] args)
    {
        this.UpdateFromInstance(method);
        methodName = method.Name;
    }

    public void OnEntry()
    {
        log.Debug("Inside" + methodName);
        log.Debug(logMessage);
    }

    public void OnExit()
    {
        Console.WriteLine("Exiting Method");
    }

    public void OnException(Exception exception)
    {
        Console.WriteLine("Exception was thrown");
    }

    private void UpdateFromInstance(MethodBase method)
    {
        this.DecoratedMethod = method;
        var declaredAttribute = method.GetCustomAttribute(this.GetType());

        foreach (var property in this._properties.Value)
            property.SetValue(this, property.GetValue(declaredAttribute));

    }

}

Now I can use custom attribute like

 [Log(logMessage = "This is Debug Message")]

Pass parameters to the constructor in Method Decorator Fody

1 Answers1