because I always shows "0"

Question

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace SoloLearn
{
class Program
{
static void Main(string[] args)
{
int num = 0;
while(num < 6)
Console.WriteLine(num);
num++;
}
}
}

Answer 1

Because you forgot the curly braces for the while loop. The corrected code:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace SoloLearn
{
class Program
{
static void Main(string[] args)
{
int num = 0;
while(num < 6)
{
Console.WriteLine(num);
num++;
}
}
}
}

Answer 2

To add to James's answer; we are allowed to omit curly braces only if the syntax within is on 1 line.

Here's and example, notice that my second 'if' statement has no curly braces:

http://www.sololearn.com/app/csharp/playground/cF71B5FwjdfU/

Answer 3

thanx for comments .

Answer 4

great !! Malachi thanx for your comments

Answer 5

when your code is more than 1 line you must put your code between the braces