Get only Methods with specific signature out of Type.GetMethods()

Question

I want to list all methods of a type with a specific method signature.

For example, if a type has a few public methods:

public void meth1 (int i);
pu         


        

Answer 1

This is the extension method to use improved from EvgK's answer.

 private static IEnumerable<MethodInfo> GetMethodsBySig(this Type type,
                                                                Type returnType,
                                                                Type customAttributeType,
                                                                bool matchParameterInheritence,
                                                                params Type[] parameterTypes)
        {
            return type.GetMethods().Where((m) =>
            {
                if (m.ReturnType != returnType) return false;

            if ((customAttributeType != null) && (m.GetCustomAttributes(customAttributeType, true).Any() == false))
                return false;

            var parameters = m.GetParameters();

            if ((parameterTypes == null || parameterTypes.Length == 0))
                return parameters.Length == 0;

            if (parameters.Length != parameterTypes.Length)
                return false;

            for (int i = 0; i < parameterTypes.Length; i++)
            {
                if (((parameters[i].ParameterType == parameterTypes[i]) ||
                (matchParameterInheritence && parameterTypes[i].IsAssignableFrom(parameters[i].ParameterType))) == false)
                    return false;
            }

            return true;
        });
    }

Use it like

var methods = SomeTypeToScan.GetMethodsBySig(
                typeof(SomeReturnType),
                typeof(SomeSpecialAttributeMarkerType),
                true, 
                typeof(SomeParameterType))
                .ToList();

Answer 2

You'll have to inspect all MethodInfos yourself. By calling MethodInfo.GetParameters() you'll get a collection of ParameterInfo objects, which in turn have a property ParameterType.

The same for the return type: inspect the ReturnType property of MethodInfo.

Answer 3

type.GetMethods().Where(p =>
                p.GetParameters().Select(q => q.ParameterType).SequenceEqual(new Type[] { typeof(int), typeof(string) }) &&
                p.ReturnType == typeof(void)
            );

Answer 4

Given this class:

public class Foo
{
    public void M1(int i){}
    public void M2(int i, string s){}
    public void M3(int i, string s){}
    public int M4(int i, string s){ return 0; }
}

A bit of Reflection and LINQ can be used:

Type t = typeof (Foo);
var theMethods = t.GetMethods().Where(mi =>
                            {
                                var p = mi.GetParameters();
                                if (p.Length != 2)
                                    return false;

                                if (p[0].ParameterType != typeof(int) 
                                     || p[1].ParameterType != typeof(string))
                                    return false;

                                return mi.ReturnType == typeof (void);
                            });

or the other syntax (which is actually nicer in this case)

var theMethods = from mi in t.GetMethods()
                    let p = mi.GetParameters()
                    where p.Length == 2
                        && p[0].ParameterType == typeof (int)
                        && p[1].ParameterType == typeof (string)
                        && mi.ReturnType == typeof (void)
                    select mi;

Test:

foreach (var methodInfo in theMethods)
{
    Console.WriteLine(methodInfo.Name);
}

Output:

M2
M3

Answer 5

You can use something like this:

public static class Extensions
{
    public static IEnumerable<MethodInfo> GetMethodsBySig(this Type type, Type returnType, params Type[] parameterTypes)
    {
        return type.GetMethods().Where((m) =>
        {
            if (m.ReturnType != returnType) return false;
            var parameters = m.GetParameters();
            if ((parameterTypes == null || parameterTypes.Length == 0))
                return parameters.Length == 0;
            if (parameters.Length != parameterTypes.Length)
                return false;
            for (int i = 0; i < parameterTypes.Length; i++)
            {
                if (parameters[i].ParameterType != parameterTypes[i])
                    return false;
            }
            return true;
        });
    }
}

And use it like this:

var methods =  this.GetType().GetMethodsBySig(typeof(void), typeof(int), typeof(string));