Type Casting Issue

[firoz.raj]

i am still little confuse.why we write short inside the small braket (short).Can someone tell me why this happens? Clarify Please.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace CastingDemo
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
           Int16 a= 10;
           Int32  b= 20;
           Int16 c;
           c = (short)(a + b);
           MessageBox.Show(c.ToString());
            
        }
    }
}

additional why this following code is not working ???.

private void Form1_Load(object sender, EventArgs e)
        {
           Int16 a= 10;
           Int32  b= 20;
           Int32  c;
           c = (long)(a + b);
           MessageBox.Show(c.ToString());
         }