will you please tell me why the conversion does not work ,in this code!! (I'm abegginer!!!!):)

using System;

namespace ConsoleApplication4
{
    /// <summary>
    /// Summary description for Class1.
    /// </summary>
    class Class1
    {
        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main(string[] args)
        {
            string strPoly;
            int[] Int = new int [10];
            int[] num = new int [3];
            int c=0; //flag for checking number of integers;
            int temp=0;
            int i=0,exp =1;
            int j=0;
            int flag=0;
            strPoly = Console.ReadLine();
            foreach ( char obj in strPoly)
            {
                switch (obj)
                {
                    case '+' :
                    case '=' :
                    case '-' :
                    case '^' :
                    case '*' :
                        flag =1;
                        goto conversion;

                    default:
                        if ( 47 < obj & obj < 58)
                        {
                            Console.WriteLine("temp:{0}",temp);
                            Int[i] = Convert.ToInt32(obj);///THIS IS THE LINE
                            Console.WriteLine("temp1={0}",temp);
                            i++;
                        }
                        else
                            Console.WriteLine("there is an invalid or Unknown character '{0}' in the polynomial you enter!",obj);
                        break;
                }
            conversion :

                if (flag == 1)
                {
                    exp=1;
                    j=0;
                    for( temp =i-1; temp >= 0;temp--)
                    {
                        num[c] =Convert.ToChar(Int[temp])*exp + num[c];
                        exp =exp * 10;
                    }
                    Console.WriteLine("{0}th number is {1}:",c,Convert.ToInt32(num[c]));
                    c++;
                    i=0;
                    flag = 0;
                }
            }

            Console.ReadLine();

        }
    }
}

> if ( 47 < obj & obj < 58)

You probably don't mean to logically AND those two expressions. You probably want something like this:

      if ((47 < obj) && (obj < 58))

> Int[i] = Convert.ToInt32(obj);///THIS IS THE LINE

...and what is the error message you get? Does it happen at compilation time or run time? What exactly happens?

Having said all that, it looks like you'd be better off using a regular expression anyway.

Try this one on for size:

// sample begins

using System;
using System.Text.RegularExpressions;

namespace ParsePoly
{
  class ParsePoly
  {
    public static void Main()
    {
      string poly = "";
      while(poly == "")
      {
        Console.Write("Enter your polynomial: ");
        poly = Console.ReadLine();
      }
      Regex rx = new Regex(@"[^\^\+\-\*\=0-9]");
      MatchCollection m = rx.Matches(poly);
      if (m.Count > 0)
        Console.WriteLine("ParsePoly: illegal polynomial");
      else
      {
        string [] numbers = poly.Split('^','*','+','-','=');
        int i = 0;
        foreach(string s in numbers)
        {
          Console.WriteLine("{0}th number is {1}", ++i, s);
        }
      }
    }
  }
}

// sample ends - example output follows

C:>parsepoly
Enter your polynomial: 123+234-345*456^567=678
1th number is 123
2th number is 234
3th number is 345
4th number is 456
5th number is 567
6th number is 678

C:>parsepoly
Enter your polynomial: 123f
ParsePoly: illegal polynomial

HTH,
()x
Also a beginner.