lambda expression with parameters

If there is a single parameter for lambda expression, just name of the parameter is sufficient as shown in below example:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApplication10
{
    class Program
    {
        static void Main(string[] args)
        {
            Func<string, string> oneParam = s =>
            String.Format("change uppercase {0}", s.ToUpper());
            
            Console.WriteLine(oneParam("test"));
        }            
    }
}

However, if we need to use two parameters, we put parameter names inside brackets:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApplication10
{
    class Program
    {
        static void Main(string[] args)
        {
            Func<double, double, double> twoParams = (x, y) => x * y;
            
            Console.WriteLine(twoParams(3, 2));
        }
        
    }
}

We can also write the data types with the parameter names. This helps compiler to match with the exact overloaded version:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApplication10
{
    class Program
    {
        static void Main(string[] args)
        {
         Func<double, double, double> twoParamsWithTypes = (double x, double y) => x * y;

         Console.WriteLine(twoParamsWithTypes(4, 2));
        }
        
    }
}

If a lambda expression is of single line, we don’t need a code block with curly brackets. For example:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApplication10
{
    class Program
    {
        static void Main(string[] args)
        {
          Func<double, double> square = x => x * x;
          
          Console.WriteLine( square(10) ); 
        }
        
    }
}

The above code is alternate notation for the following code. However, the above code is more readable.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApplication10
{
    class Program
    {
        static void Main(string[] args)
        {
            Func<double, double> square = x =>
            {
             return x * x;
            }
            
            Console.WriteLine( square(10) ); 
        }
        
    }
}

If we have multiple statements in the implementation of a lambda expression, then we need  a return statement as well as curly brackets:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApplication10
{
    class Program
    {
        static void Main(string[] args)
        {
           Func<string, string> lambda = param =>
           {
           param += " HELLO ";
           param += " and this was added to the string.";
           return param;
           };
        
           Console.WriteLine(param(" PAKISTAN ") );

        }
        
    }
}