Removing all whitespace lines from a multi-line string efficiently

Question

In C# what\'s the best way to remove blank lines i.e., lines that contain only whitespace from a string? I\'m happy to use a Regex if that\'s the best solution.

EDIT

Answer 1

Here's another option: use the StringReader class. Advantages: one pass over the string, creates no intermediate arrays.

public static string RemoveEmptyLines(this string text) {
    var builder = new StringBuilder();

    using (var reader = new StringReader(text)) {
        while (reader.Peek() != -1) {
            string line = reader.ReadLine();
            if (!string.IsNullOrWhiteSpace(line))
                builder.AppendLine(line);
        }
    }

    return builder.ToString();
}

Note: the IsNullOrWhiteSpace method is new in .NET 4.0. If you don't have that, it's trivial to write on your own:

public static bool IsNullOrWhiteSpace(string text) {
    return string.IsNullOrEmpty(text) || text.Trim().Length < 1;
}