C implements the template method with Lambda and the delegate

1 problem description
Take a look at this code:

int[] a = [1,2,3];
for (int i =0; i<a.length; i++)
  {
    a[i] = a[i] * 2;
  }
for (int i =0; i<a.length; i++)
  {
    Console.WriteLine(a[i]);
  }

Obviously, there is a duplication of the for loop in the code above.

2 solutions
How do you eliminate repetition? Use the delegate.

The & # 8226; Define the entrusted

delegate int mapfun(int x);// To replace the different parts of the code above 

The & # 8226; Template method

// It's just traversing 
void map(mapfun fn, int[] a)
{
  for (int i = 0; i < a.Length; ++i)
    {
      a[i] = fn(a[i]);
    }
}

The & # 8226; Client code

int[] a = {1, 2, 3};
map(delegate(int x) { return x * 2; }, a);  //.Net 2.0 Support for delegating anonymous methods 
map(x => { Console.WriteLine(x); return x; }, a); //.Net 3.0 To support lambda expression 

3 complete code example

class Program
{
  static void Main(string[] args)
  {
    int[] a = {1, 2, 3};
    map(delegate(int x) { return x * 2; }, a);  //.Net 2.0 Support for delegating anonymous methods 
    map(x => { Console.WriteLine(x); return x; }, a); //.Net 3.0 To support lambda expression 
  }
  delegate int mapfun(int x);
  static void map(mapfun fn, int[] a)
  {
    for (int i = 0; i < a.Length; ++i)
      {
        a[i] = fn(a[i]);
      }
  }
}

4. Comparison with traditional template methods
1. Reduce the number of subclasses. In the template method, one subclass is needed to extend a set of algorithms.
2. The template hides the algorithm and delegates it to the client code for selection.