List<int> numbers = new List<int> { 1, 5, 6, 3, 8, 7, 9, 2, 3, 4, 5, 6, };

// To get the count of those that are less than four we might write:
int lessThanFourCount = numbers.Where(n => n < 4).Count();

// But this can also be written as:
Func<int, bool> lessThanFour = n => n < 4;

int lessThanFourCount = numbers.Where(lessThanFour).Count();

...
DoSomethingPotentiallyBad((x) => x * 2, 0); // both delegates do
DoSomethingPotentiallyBad((x) => 2 / x, 0); // something different ...
...

    static int DoSomethingPotentiallyBad(Func<int, int> function, int input)
    {
      // ... but get exception handled all the same way
      try
        {
            return function.Invoke(input);
        }
        catch
        {
            Console.WriteLine("Evaluation failed! Return 0.");
            return 0;
        }
    }

public static string ToDelimitedString<T>(
    this IEnumerable<T> source, Func<T, string> converter, string separator)
{
    // error checking removed for readability

    StringBuilder sb = new StringBuilder();
    foreach (T item in source)
    {
        sb.Append(converter(item));
        sb.Append(separator);
    }

    return (sb.Length > 0) ?
        sb.ToString(0, sb.Length - separator.Length) : string.Empty;
}

// ...

List<int> e1 = new List<int> { 1, 2, 3 };
// convert to "2|4|6"
string s1 = e1.ToDelimitedString(x => (x * 2).ToString(), "|");

DateTime[] e2 = new DateTime[]
    { DateTime.Now.AddDays(-100), DateTime.Now, DateTime.Now.AddDays(100) };
// convert to "Tuesday, Thursday, Saturday"
string s2 = e2.ToDelimitedString(x => x.DayOfWeek.ToString(), ", ");

List<MyCustomType> e3 = new List<MyCustomType>
    { new MyCustomType("x"), new MyCustomType("y"), new MyCustomType("z") };
// convert to "X and Y and Z"
string s3 = e3.ToDelimitedString(x => x.Name.ToUpper(), " and ");