How To Use Local Functions In C# 7.0

What are Local Functions in C# 7.0?

The local function is an ability to declare methods inside an already defined function’s body. We are able to write local functions in C# 6.0 too but they can’t have a complete body or function name, and can only be anonymous.

Why Local Functions in C# 7.0?

As per the Microsoft blog, this is already (kind of) possible by using the Func and Action types with anonymous methods.



However, they lack a few features,

• Generics
• ref and out parameters
• params

How to write Local Functions in C# 7.0

Local functions have the same capabilities as normal methods but will only be scoped to the block they were declared in.

Now, let’s try to write a normal local function first.

In the following image of code, you can check that I just created a function with two argument types (int, string) and it has all the behavior as a normal function. Since it is a local function, you can use or call it within the same function only.



Code

static void Main(string[] args)
        {
            string myFunc(int p1,string p2)
            {
                return p2.Substring(p1);
            }

            Console.WriteLine(myFunc(2,"Nitin Pandit"));
            Console.Read();
        }

We can also use other properties of local function, like Generics, ref/out parameters, and params. So, let’s see how to use them.

1. Local Generics Functions
   Local Generic function is really a nice property. It can be used in the same way as in a normal function and we can call it within the root function. In the following example, I have created myFunc as Generic.
   
   
   
   Code
   

   static void Main(string[] args)
           {
               void myFunc<T>(T value)
               {
                   Console.WriteLine(value);
               }
   
   
               myFunc<string>("Nitin Pandit");
               Console.Read();
           }

2. Using out/ref in Local Functions
   
   
   
   Code
   

   static void Main(string[] args)
           {
               void myFunc(int value1, out int value2)
               {
                   value2 = value1 + value1;
                   Console.WriteLine();
               }
               int i = 0;
               myFunc(12, out i);
               Console.WriteLine($"New Value of i : {i}");
               Console.Read();
           }

3. Using params in Local Functions
   
   
   
   Code
   

   static void Main(string[] args)
           {
               void myFunc(params int[] items)
               {
                   int res = 0;
                   foreach (var item in items)
                   {
                       res += item;
                   }
                   Console.WriteLine($"Total : {res}");
               }
   
               myFunc(1,2,3,4,5,6,7,8,9);
   
               Console.Read();
           }

All these properties of local function make C# 7.0 more powerful. Thanks for reading this article. Stay tuned with us for more updates:

Connect (“Nitin Pandit”);