Contains method in lambda expression

Question

I use this method to extract table name and field name from formula.

public List<string> ExtractFieldsFromFormula(string formula)
{
 List<string> formulas = new List<string>();
 formulas.AddRange(formula.Split(new char[] {'{', '}'}).Where(f=>!f.Contains("+") && !f.Contains("-")&&!f.Contains("/")&&!f.Contains("*")&& !f.Contains("(")&& !f.Contains(")") && f.Trim()!=String.Empty));
 return formulas;
}

my formula is like this:

"{City.a}+5*(2/{City.b})"

and result of method is a list :

• City.a
• City.b

how can i write this code better than this?!!

Answer 1

And there's always a place for a regular expression (especially when searching for a pattern in a string of characters ;-)).

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
namespace ConsoleApplication9
{
 class Program
 {
 static void Main(string[] args)
 {
 string pattern = @"\{(?<expr>[a-zA-Z0-9.]+?)\}";
 string formula = @"{City.a}+5*(2/{City.b})";
 var matches = Regex.Matches(formula, pattern).OfType<Match>();
 foreach (var match in matches)
 {
 Console.WriteLine(match.Groups["expr"]);
 }
 // prints
 // City.a
 // City.b
 string splitPattern = @"\{(?<object>[a-zA-Z0-9]+?)\.(?<field>[a-zA-Z0-9]+?)\}";
 matches = Regex.Matches(formula, splitPattern).OfType<Match>();
 foreach (var match in matches)
 {
 Console.WriteLine("Object: {0} Field: {1}", match.Groups["object"], match.Groups["field"]);
 }
 // prints
 // Object: City Field: a
 // Object: City Field: b
 }
 }
}

• ANeves: Named matches?!? You made my day.

Answer 2

This should a) make it a bit more compact and b) be a bit faster.

 private static readonly char[] splitChars = new[] { '{', '}' };
 private static readonly char[] charsToExclude = new[] { '+', '-', '/', '*', '(', ')' };
 public static List<string> ExtractFieldsFromFormula(string formula)
 {
 var formulas = new List<string>();
 formulas.AddRange(formula.Split(splitChars).Where(f => (f.Trim().Length > 0) && (f.IndexOfAny(charsToExclude) == -1)));
 return formulas;
 }