Check if string is empty or all spaces in C#

Question

How to easily check if a string is blank or full of an undetermined amount of spaces, or not?

Answer 1

If you literally need to know if the "string is blank or full of an undetermined amount of spaces", use LINQ as @Sonia_yt suggests, but use All() to ensure that you efficiently short-circuit out as soon as you've found a non-space.

(This is give or take the same as Shimmy's, but answers the OP's question as written to only check for spaces, not any and all whitespace -- \t, \n, \r, etc.)

/// 

/// Ensure that the string is either the empty string `""` or contains
/// *ONLY SPACES* without any other character OR whitespace type.
/// 
/// The string to check.
/// `true` if string is empty or only made up of spaces. Otherwise `false`.
public static bool IsEmptyOrAllSpaces(this string str)
{
    return null != str && str.All(c => c.Equals(' '));
}

And to test it in a console app...

Console.WriteLine("    ".IsEmptyOrAllSpaces());      // true
Console.WriteLine("".IsEmptyOrAllSpaces());          // true
Console.WriteLine("  BOO  ".IsEmptyOrAllSpaces());   // false

string testMe = null;
Console.WriteLine(testMe.IsEmptyOrAllSpaces());      // false