using System;

using System.Linq.Expressions;

​

namespace somenamespace

{

    public class someclass

    {

        private static Func<somestructone, Delegate, somestructone> cachedSetter;

        public delegate void somedelegate(int somevariable);

        public static void somefunction(int somevariable)

        {

            Console.WriteLine("somevalue: {0}", somevariable);

        }

        public struct somestructone

        {

            public somedelegate somedelegate;

        }

​

        public static void Main(string[] args)

        {

            if (cachedSetter == null)

                cachedSetter = GenerateFieldSetter();

            var @delegate = Delegate.CreateDelegate(typeof(somedelegate), typeof(someclass).GetMethod("somefunction"));

            var structone = new somestructone();

            structone = cachedSetter(structone, @delegate);

            Console.WriteLine(structone.somedelegate == null);

        }

        public static Func<somestructone, Delegate, somestructone> GenerateFieldSetter()

        {

            var field = typeof(somestructone).GetField("somedelegate");

            var delegateParameter = Expression.Parameter(typeof(Delegate), "delegate");

            var structParameter = Expression.Parameter(typeof(somestructone), "struct");

            var setExpression = Expression.Assign(Expression.Field(structParameter, field), Expression.Convert(delegateParameter, typeof(somedelegate)));

            var block = Expression.Block(setExpression, structParameter);

            return Expression.Lambda<Func<somestructone, Delegate, somestructone>>(block, structParameter, delegateParameter).Compile();

        }

    }

}

​