C# snippet needed to replicate VBA Like operator

Question

I am converting VBA code that contains the LIKE operator, as in

    dim sToken as String
    if sToken Like "(*,*)" then ...

In all cases the patterns use only the * wildcard which matches any string (including the empty string). The VBA Like operator yields only a true/false result so it's up to the subsequent VBA code to parse further and pluck out the matching substrings whenever there's a match.

I'd be most appreciative if someone can provide a C# snippet to test for the same type of simple wildcard match. If the snippet also yields matching substrings - even better.

Answer 1

Several people have suggested regular expressions which should work well for this scenario. Another option is to use the VB Like operator directly from C# code. This can be done by invoking the Compiler helper LikeOperator.LikeString. This function is located in the VB runtime assembly, Microsoft.VisualBasic.dll, and is usable from C#.

using Microsoft.VisualBasic.CompilerServices;

...

if (LikeOperator.LikeString(sToken, "(*,*)")) { 
  ...
}

I don't believe this version has 100% parity with the VBA version of Like but it will be extremely close and will match for the common scenarios.

Answer 2

Well, that particular pattern could be matched with

if (sToken.StartsWith("(") && sToken.EndsWith(")")
    && sToken.Contains(","))

but in general you may find it makes more sense to use regular expressions. For example:

using System;
using System.Text.RegularExpressions;

class Program
{
    static void Main(string[] args)
    {
        Regex regex = new Regex(@"^\(.*,.*\)$");

        Console.WriteLine(regex.IsMatch("x(a,b)")); // False due to the x
        Console.WriteLine(regex.IsMatch("(a,b)x")); // False due to the x
        Console.WriteLine(regex.IsMatch("(ab)"));   // False due to the lack of ,
        Console.WriteLine(regex.IsMatch("(a,b"));   // False due to the lack of )
        Console.WriteLine(regex.IsMatch("(a,b)"));   // True!
        Console.WriteLine(regex.IsMatch("(aaa,bbb)"));   // True!
        Console.WriteLine(regex.IsMatch("(,)"));   // True!
    }
}

Things to note with the pattern here:

• I've used a verbatim string literal (the @ at the start) to make it easier to perform escaping within the regex
• ^ and $ force it to match the whole string
• The brackets are escaped so they're not treated as grouping operators

The MSDN "Regular Expression Language Elements" page is a good reference for .NET regexes.