X size pyramid

Question

when user types number X, outputs a pyramid of size of X

if X is 6,

 

*

**

***

****

*****

******

 

using System;

class example4
{
   public static void Main()
   {

   int i;
   int j;
   int k;
   Console.WriteLine("type number of size");

   object a = (object)Console.Read();

   int b = (int) a;

   for (i = 0; i <= b;i++)

   {

      for (j = 0; j < b+1-i;j++)
               {

               Console.Write("");

               }

      for (k = 0; k < i; k++)

               {
               Console.Write("*");

               }

          Console.WriteLine("\n");

     }
}

} 

 

but this doesn`t work

how should I solve that problem?