String.IsNullOrEmpty（）检查空格

Question

What is needed to make String.IsNullOrEmpty() count whitespace strings as empty?

Eg. I want the following to return true instead of the usual false :

String.IsNullOrEmpty(" ");

Is there a better approach than:

 String.IsNullOrEmpty(" ".Trim());

(Note that the original question asked what the return would be normally hence the unsympathetic comments, this has been replaced with a more sensible question).

Answer 1

.NET 4.0 will introduce the method String.IsNullOrWhiteSpace . Until then you'll need to use Trim if you want to deal with white space strings the same way you deal with empty strings.

For code not using .NET 4.0, a helper method to check for null or empty or whitespace strings can be implemented like this:

public static bool IsNullOrWhiteSpace(string value)
{
    if (String.IsNullOrEmpty(value))
    {
        return true;
    }

    return String.IsNullOrEmpty(value.Trim());
}

The String.IsNullOrEmpty will not perform any trimming and will just check if the string is a null reference or an empty string.

Answer 2

String.IsNullOrEmpty(" ")

...Returns False

String foo = null;
String.IsNullOrEmpty( foo.Trim())

...Throws an exception as foo is Null.

String.IsNullOrEmpty( foo ) || foo.Trim() == String.Empty

...Returns true

Of course, you could implement it as an extension function:

static class StringExtensions
{
    public static bool IsNullOrWhiteSpace(this string value)
    {
        return (String.IsNullOrEmpty(value) || String.IsNullOrEmpty(value.Trim()));
    }
}