[TestMethod]
        public void DemoLINQExtensionMethods()
        {
            List<int> ints = new List<int>(new int[] { 1, 11, 12 });
            //Standard Delegate
            int val = ints.FirstOrDefault(ThisOneGoesToEleven);
            Assert.IsTrue(val == 11, "Eleven was not found. Value = " + val.ToString());
            //Using Anonymous Method
            val = ints.FirstOrDefault(delegate(int i) { return i == 11; });
            Assert.IsTrue(val == 11, "Eleven was not found. Value = " + val.ToString()); 
            //Using equivalent Lambda syntax
            val = ints.FirstOrDefault(x => x == 11);
            Assert.IsTrue(val == 11, "Eleven was not found. Value = " + val.ToString());
        }
        private bool ThisOneGoesToEleven(int volume)
        {
            return volume == 11;
        }

[TestMethod]
        public void DemoLINQExtensionMethods()
        {
            List<int> ints = new List<int>(new int[]{1,11,12});
            int val = ints.FirstOrDefault(ThisOneGoesToEleven); 
            Assert.IsTrue(val == 11, "Eleven was not found. Value = " + val.ToString());
            //Using equivalent Lambda syntax
            val = ints.FirstOrDefault(x => x == 11);
            Assert.IsTrue(val == 11, "Eleven was not found. Value = " + val.ToString());
        }
        private bool ThisOneGoesToEleven(int volume)
        {
            return volume == 11; 
        }

LINQ Extension method called with delegate, anonymous delegate, and lambda delegate.

Note that this only returns a "default" in the sense that it does not throw an exception if no item in the source matches the selection criteria.  .First() does throw an exception in this case.

LINQ Extension Methods

C#