C# remove empty url parameters regex

Question

I am trying to remove empty url type parameters from a string using C#. My code sample is here.

    public static string test ()
    {
        string parameters          


        

Answer 1

Regex:

(?:^|&)[a-zA-Z]+=(?=&|$)

This matches start of string or an ampersand ((?:^|&)) followed by at least one (english) letter ([a-zA-Z]+), an equal sign (=) and then nothing, made sure by the positive look-ahead ((?=&|$)) which matches end of string or a new parameter (started by &).

Code:

public static string test ()
{
    string parameters = "one=aa&two=&three=aaa&four=";
    string pattern = "(?:^|&)[a-zA-Z]+=(?=&|$)";
    string replacement = "";
    Regex rgx = new Regex(pattern);
    string result = rgx.Replace(parameters, replacement);

    return result;
}

public static void Main(string[] args)
{
    Console.WriteLine(test());
}

Note that this also returns the correct variable (as pointed out by Joel Anderson)

See it live here at ideone.