How to Efficiently Parse Command-Line Parameters into a String Array in C#?

C# command line parameters are parsed into string arrays

In C#, it is often necessary to split a string containing command line parameters into a string array. This article explores standard functions and recommended methods to accomplish this task.

An important consideration is handling double-quoted strings containing spaces. Simply splitting a string based on whitespace is not enough, as it will incorrectly split double-quoted strings.

Standard functions

C# does not provide a standard function specifically for this purpose. This functionality can be achieved using a custom function that checks each character.

Recommended method

A recommended approach is to use the following code block:

public static IEnumerable<string> SplitCommandLine(string commandLine)
{
    bool inQuotes = false;

    return commandLine.Split(c =>
    {
        if (c == '\"')
            inQuotes = !inQuotes;

        return !inQuotes && c == ' ';
    })
    .Select(arg => arg.Trim().TrimMatchingQuotes('\"'))
    .Where(arg => !string.IsNullOrEmpty(arg));
}

This method splits the string based on a function that checks for quotes and spaces, then trims the spaces and quotes.

Custom extension method

Another approach is to create a custom extension method:

public static IEnumerable<string> Split(this string str, Func<char, bool> controller)
{
    int nextPiece = 0;

    for (int c = 0; c < str.Length; c++)
    {
        if (controller(str[c]))
        {
            yield return str.Substring(nextPiece, c - nextPiece);
            nextPiece = c + 1;
        }
    }
    yield return str.Substring(nextPiece);
}

public static string TrimMatchingQuotes(this string input, char quote)
{
    if ((input.Length >= 2) && (input[0] == quote) && (input[input.Length - 1] == quote))
        return input.Substring(1, input.Length - 2);

    return input;
}

Command line strings can be split using these methods:

string[] parameterArray = SplitCommandLine(parameterString).ToArray();

Example usage

The following example demonstrates the use of the above method:

string parameterString = @"/src:""C:\tmp\Some Folder\Sub Folder"" /users:""[email protected]"" tasks:""SomeTask,Some Other Task"" -someParam foo";

string[] parameterArray = SplitCommandLine(parameterString).ToArray();

foreach (string parameter in parameterArray)
{
    Console.WriteLine(parameter);
}

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