How do I parse mathematical expressions in C #?

Here is some code I wrote a while ago for parsing infix operators (operator operand operator). There are some small classes and helper functions, but they are quite simple to implement. If you need this or any help with it, let me know and I can download them somewhere.

This is the basic Dijkstra implementation of the Shunting-yard algorithm

public Operand ExpressionTree
{
    get;
    private set;
}

private Stack<Operands.Operand> stack = new Stack<InfixParser.Operands.Operand>();
private Queue<Operands.Operand> outputQueue = new Queue<InfixParser.Operands.Operand>();

private void ParseFormulaString()
{
    //Dijkstra Shunting Yard Algorithm
    Regex re = new Regex(@"([\+\-\*\(\)\^\/\ ])");
    List<String> tokenList = re.Split(formulaString).Select(t => t.Trim()).Where(t => t != "").ToList();

    for (int tokenNumber = 0; tokenNumber < tokenList.Count(); ++tokenNumber)
    {
        String token = tokenList[tokenNumber];
        TokenClass tokenClass = GetTokenClass(token);

        switch (tokenClass)
        {
            case TokenClass.Value:
                outputQueue.Enqueue(new Value(token));
                break;
            case TokenClass.Function:
                stack.Push(new Function(token, 1));
                break;
            case TokenClass.Operator:
                if (token == "-" && (stack.Count == 0 || tokenList[tokenNumber - 1] == "("))
                {
                    //Push unary operator 'Negative' to stack
                    stack.Push(new Negative());
                    break;
                }
                if (stack.Count > 0)
                {
                    String stackTopToken = stack.Peek().Token;
                    if (GetTokenClass(stackTopToken) == TokenClass.Operator)
                    {
                        Associativity tokenAssociativity = GetOperatorAssociativity(token);
                        int tokenPrecedence = GetOperatorPrecedence(token);
                        int stackTopPrecedence = GetOperatorPrecedence(stackTopToken);

                        if (tokenAssociativity == Associativity.Left && tokenPrecedence <= stackTopPrecedence ||
                            tokenAssociativity == Associativity.Right && tokenPrecedence < stackTopPrecedence)
                        {
                            outputQueue.Enqueue(stack.Pop());
                        }
                    }
                }
                stack.Push(new BinaryOperator(token, Operator.OperatorNotation.Infix));
                break;
            case TokenClass.LeftParen:
                stack.Push(new LeftParenthesis());
                break;
            case TokenClass.RightParen:
                while (!(stack.Peek() is LeftParenthesis))
                {
                    outputQueue.Enqueue(stack.Pop());
                }
                stack.Pop();

                if (stack.Count > 0 && stack.Peek() is Function)
                {
                    outputQueue.Enqueue(stack.Pop());
                }
                break;
        }

        if (tokenClass == TokenClass.Value || tokenClass == TokenClass.RightParen)
        {
            if (tokenNumber < tokenList.Count() - 1)
            {
                String nextToken = tokenList[tokenNumber + 1];
                TokenClass nextTokenClass = GetTokenClass(nextToken);
                if (nextTokenClass != TokenClass.Operator && nextTokenClass != TokenClass.RightParen)
                {
                    tokenList.Insert(tokenNumber + 1, "*");
                }
            }
        }
    }

    while (stack.Count > 0)
    {
        Operand operand = stack.Pop();
        if (operand is LeftParenthesis || operand is RightParenthesis)
        {
            throw new ArgumentException("Mismatched parentheses");
        }

        outputQueue.Enqueue(operand);
    }

    String foo = String.Join(",", outputQueue.Select(t => t.Token).ToArray());
    String bar = String.Join("", tokenList.ToArray());

    Stack<Operand> expressionStack = new Stack<Operand>();
    while (outputQueue.Count > 0)
    {
        Operand operand = outputQueue.Dequeue();

        if (operand is Value)
        {
            expressionStack.Push(operand);
        }
        else
        {
            if (operand is BinaryOperator)
            {
                BinaryOperator op = (BinaryOperator)operand;
                Operand rightOperand = expressionStack.Pop();
                Operand leftOperand = expressionStack.Pop();
                op.LeftOperand = leftOperand;
                op.RightOperand = rightOperand;
            }
            else if (operand is UnaryOperator)
            {
                ((UnaryOperator)operand).Operand = expressionStack.Pop();
            }
            else if (operand is Function)
            {
                Function function = (Function)operand;
                for (int argNum = 0; argNum < function.NumArguments; ++argNum)
                {
                    function.Arguments.Add(expressionStack.Pop());
                }
            }

            expressionStack.Push(operand);
        }
    }

    if (expressionStack.Count != 1)
    {
        throw new ArgumentException("Invalid formula");
    }

    ExpressionTree = expressionStack.Pop();
}

private TokenClass GetTokenClass(String token)
{
    double tempValue;
    if (double.TryParse(token, out tempValue) ||
        token.Equals("R", StringComparison.CurrentCultureIgnoreCase) ||
        token.Equals("S", StringComparison.CurrentCultureIgnoreCase))
    {
        return TokenClass.Value;
    }
    else if (token.Equals("sqrt", StringComparison.CurrentCultureIgnoreCase))
    {
        return TokenClass.Function;
    }
    else if (token == "(")
    {
        return TokenClass.LeftParen;
    }
    else if (token == ")")
    {
        return TokenClass.RightParen;
    }
    else if (binaryInfixOperators.Contains(token))
    {
        return TokenClass.Operator;
    }
    else
    {
        throw new ArgumentException("Invalid token");
    }
}

private Associativity GetOperatorAssociativity(String token)
{
    if (token == "^")
        return Associativity.Right;
    else
        return Associativity.Left;
}

private int GetOperatorPrecedence(String token)
{
    if (token == "+" || token == "-")
    {
        return 1;
    }
    else if (token == "*" || token == "/")
    {
        return 2;
    }
    else if (token == "^")
    {
        return 3;
    }
    else
    {
        throw new ArgumentException("Invalid token");
    }
}