gistfile1.cs

var foo = new Foo();
var bar = typeof(Foo).GetMethod("Bar");

var s = Stopwatch.StartNew();
for (int i = 0; i < 5000000; i++)
    foo.Bar(i);

Console.WriteLine("Sem reflection: {0}", s.Elapsed);

s.Restart();
for (int i = 0; i < 5000000; i++)
    bar.Invoke(foo, new object[] { i });

Console.WriteLine("Com reflection: {0}", s.Elapsed);