Calling method with attribute value in C#

Question

[AttributeUsage(AttributeTargets.Method,AllowMultiple=true)]
public class MethodId : Attribute
{
    private int mId;
    public MethodId(int mId)
    {
        this.mId = mId;
    }

    public int methodId
    {
        get { return this.mId; }
        set { this.mId = value; }
    }
}

public class Methods
{
    [MethodId(1)]
    public void square()
    {        }

    [MethodId(2)]
    public void Notify()
    {        }
}

How to access square() in main() or in any other class with the help of MethodId?

Aliostad · Accepted Answer · 2012-03-26 10:52:04Z

9

private static MethodInfo GetMethodInfo(int id)
{
        return typeof(Methods).GetMethods().
            Where(x => x.GetCustomAttributes(false).OfType<MethodId>().Count() > 0)
            .Where(x => x.GetCustomAttributes(false).OfType<MethodId>().First().methodId == id)
            .First();
}

And usage:

var methodInfo = GetMethodInfo(1);
methodInfo.Invoke(new Methods(), null);

NOTE:

This solution is only meant to display how to do it. Not omptimised for performance. Ideally you would cache the methodInfos.

answered Mar 26, 2012 at 10:52

Aliostad

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4 Comments

Milee Over a year ago

Please explain : methodInfo.Invoke(new Methods(), null);

Aliostad Over a year ago

The method is not static so you need an instance to run it, hence new Methods(). The other one is the parameters which it has none hence null.

Milee Over a year ago

Ok...But "new Methods()" is an instance created to call which method? It is just a new object.I am not able to catch this. What are we passing exactly? :)

Aliostad Over a year ago

You need to read the reflection stuff. I cannot explain it here in comments. Read about MethodInfo.

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