Escape shell parameters for calling with the Win32 "CommandLine" argument (Process.StartInfo.Arguments)

EscapeShellParam.cs

/// <summary>
/// Escapes any given string input so that it can be reversed into
/// exactly this string by the Win32 CommandLineToArgvW method. Does not
/// perform any operation on the param string if it doesn't contain
/// whitespace or quotes.
/// </summary>
/// <param name="param">
/// The parameter to escape which can simply be appended to a whitespace
/// separated process parameter string list. (plus whitespace to
/// separate)
/// </param>
/// <returns>An escaped shell parameter</returns>
/// <see>https://docs.microsoft.com/en-us/windows/win32/api/shellapi/nf-shellapi-commandlinetoargvw</see>
/// <see>https://docs.microsoft.com/en-us/previous-versions/17w5ykft(v=vs.85)</see>
public static string EscapeShellParam(string param)
{
	if (param.Length == 0)
		return "\"\"";
	// if no whitespace or quotes
	if (!param.Any(a => a <= ' ' || a == '"'))
		return param;

	StringBuilder ret = new StringBuilder(param.Length + 2);
	ret.Append('"');
	int backslash = 0;
	foreach (var c in param)
	{
		if (c == '"')
		{
			ret.Append('\\', backslash + 1);
			ret.Append('"');
			backslash = 0;
		}
		else
		{
			if (c == '\\')
				backslash++;
			else
				backslash = 0;
			ret.Append(c);
		}
	}
	if (backslash > 0)
		ret.Append('\\', backslash);
	ret.Append('"');
	return ret.ToString();
}