Recently, I got a chance to experiment with Lambda expressions in C#. It was love at first sight :P

A lambda expression is an anonymous function that you can use to create delegates or expression tree types. By using lambda expressions, you can write local functions that can be passed as arguments or returned as the value of function calls. Lambda expressions are particularly helpful for writing LINQ query expressions.

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As an example- Find the square of a number.

A normal course of action using delegates will be-

1. Create a delegate.
2. Create a function of that delegate type.
3. Make the call.

delegate int del(int i);
static int SquareOfNum(int num)
{
    return num*num;
}
static void Main(string[] args)
{
    del myDelegate = new del(SquareOfNum);
    int j = myDelegate(5); //j = 25
}

Anonymous methods make the code shorter and allow the usage of functions without giving them any names.

delegate int del(int i);
public static void Main(string[] args)
{
    del myDelegate = delegate(int num)
    {
      return num*num;
    };
    int j = myDelegate(5); //j = 25
}

Lambdas take it a step further-

delegate int del(int i);
public static void Main(string[] args)
{
    del myDelegate = x => x * x;
    int j = myDelegate(5); //j = 25
}

Notice that the data type of x was not provided. It is inferred directly from the delegate del. Also, the keyword return is not used in the above example. If the function has multiple statements, a body can be created with a return statement.

delegate int del(int i);
public static void Main(string[] args)
{
    del myDelegate = x => 
    {
      return x * x;
    };  
    int j = myDelegate(5); //j = 25
}

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This example is really silly but it helps in understanding the basics. Lambdas can prove to be really powerful when used with event-driven programming and with LINQ. They make the code shorter and easy to understand.

Finding average of even fibonacci numbers-

int[] fibNum = { 1, 1, 2, 3, 5, 8, 13, 21, 34 };
double averageValue = fibNum.Where(num => num % 2 == 1).Average();

Getting the names of all the students from a list of students (Assume that the Student class has a Name property).

List<Student> students = EnumerateStudents();
List<string> studentnames = students.Select(student => student.Name).ToList();