C# Expression Calculator

I have usually written all my programs in C++. Now, however, I decided to try out C#. I've heard a lot of great stuff about it. The first thing I tried out, was a windows forms expression calculator. The calculator first uses the Shunting-Yard algorithm to parse the inputted expression into Reverse Polish Notation, then use several stack methods to to calculate the final result. A snippet of the source code:

  Stack<string> output = new Stack<string>();
 string refr = "";
 double num1 = 0;
 double num2 = 0;
 public Form1()
 {
     InitializeComponent();
 }
 private void outpush(string val , bool more )
 {
     if(!more)
     {
         output.Push(val+" ");
     }
     else
     {
         output.Push(val);
     }
 }
 private void button1_Click(object sender, EventArgs e)
 {
     Stack<char> oper = new Stack<char>();
     char[] exp = richTextBox1.Text.Replace(" ","").ToCharArray();
     refr = "";
     for(int i = 0; i < exp.Count(); i++)
     {
         if(Char.IsNumber(exp[i]))
         {
             if(exp.Count()-1 > i && Char.IsNumber(exp[i+1]))
             {
             outpush(Convert.ToString(exp[i]), true);
             }
             else
             {
                 outpush(Convert.ToString(exp[i]), false);
             }
         }
         else switch(exp[i])
         {
             case '+':
             if(oper.Count()>0)
             {
                 if (oper.ToArray()[0] == '*' || oper.ToArray()[0] == '/' || oper.ToArray()[0] == '^')
                 {
                     outpush(Convert.ToString(oper.Pop()), false);
                 }
             }
             oper.Push(exp[i]);
             break;

             case '-':
             if (oper.Count() > 0)
             {
                 if (oper.ToArray()[0] == '*' || oper.ToArray()[0] == '/' || oper.ToArray()[0] == '^')
                 {
                     outpush(Convert.ToString(oper.Pop()), false);
                 }
             }
             oper.Push(exp[i]);
             break;

             case '-':
             if (oper.Count() > 0)
             {
                 if (oper.ToArray()[0] == '*' || oper.ToArray()[0] == '/' || oper.ToArray()[0] == '^')
                 {
                     outpush(Convert.ToString(oper.Pop()), false);
                 }
             }
             oper.Push(exp[i]);
             break;

             case '*':
             if (oper.Count() > 0)
             {
                 if (oper.ToArray()[0] == '*' || oper.ToArray()[0] == '/' || oper.ToArray()[0] == '^')
                 {
                     outpush(Convert.ToString(oper.Pop()), false);
                 }
             }
             oper.Push(exp[i]);
             break;

             case '/':
             if (oper.Count() > 0)
             {
                 if (oper.ToArray()[0] == '*' || oper.ToArray()[0] == '/' || oper.ToArray()[0] == '^')
                 {
                     outpush(Convert.ToString(oper.Pop()), false);
                 }
             }
             oper.Push(exp[i]);
             break;

             case '(':
             oper.Push(exp[i]);
             break;

             case ')':
             int count2 = oper.Count();
             if (oper.Count() > 0)
             {
                 while(oper.ToArray()[0] != '(')
                 {
                     outpush(Convert.ToString(oper.Pop()), false);
                 }
             }
             if (oper.Count() == 0) { goto errorlp; }
             oper.Pop();
             break;

             case '^':
             oper.Push(exp[i]);
             break;

             default:
             break;
         }
     }
     int count = oper.Count();
     for(int i = 0; i < count; i++)
     {
         outpush(Convert.ToString(oper.Pop()), false);
     }
     int counto = output.Count();
     for(int i = 0; i < counto; i++)
     {
         refr = output.Pop() + refr;
     }

     string[] input = refr.Split(' ');

     Stack<double> numbers = new Stack<double>();
     for(int i = 0; i < input.Count(); i++)
     {
         if(input[i] != ""){
         if(Char.IsNumber(input[i],0))
         {
             numbers.Push(Convert.ToDouble(input[i]));
         }
         else switch(input[i])
         {
             case "+":
                 if (numbers.Count() < 2) { goto errornum; }
                 num1 = numbers.Pop();
                 num2 = numbers.Pop();
                 numbers.Push(num2 + num1);
             break;

             case "-":
             if (numbers.Count() < 2) { goto errornum; }
                 num1 = numbers.Pop();
                 num2 = numbers.Pop();
                 numbers.Push(num2-num1);
             break;

             case "-":
             if (numbers.Count() < 2) { goto errornum; }
                 num1 = numbers.Pop();
                 num2 = numbers.Pop();
                 numbers.Push(num2-num1);
             break;

             case "*":
             if (numbers.Count() < 2) { goto errornum; }
                 num1 = numbers.Pop();
                 num2 = numbers.Pop();
                 numbers.Push(num2*num1);
             break;

             case "/":
             if (numbers.Count() < 2) { goto errornum; }
                 num1 = numbers.Pop();
                 num2 = numbers.Pop();
                 numbers.Push(num2/num1);
             break;


             case "^":
             if (numbers.Count() < 2) { goto errornum; }
                 num1 = numbers.Pop();
                 num2 = numbers.Pop();
                 numbers.Push(Math.Pow(num2,num1));
             break;
         }
         }
     }
     if (numbers.Count() != 1) { goto errornum; }
         richTextBox1.Text = Convert.ToString(numbers.Pop());

         goto Ends;

     errorlp:
         richTextBox1.Text = "Error!\nMissing left parenthesis!";
         goto Ends;

     Errorrp:
         richTextBox1.Text = "Error!\nMissing right parenthesis!";
         goto Ends;

     errornum:
         richTextBox1.Text = "Error!\nNumber count does not equal operator count!";

     Ends:
         num1 = 0;

And here's an image of the calculator interface: