Difference between IsNullOrEmpty and IsNullOrWhiteSpace in C#

• Source: MSDN

IsNullOrWhiteSpace is a convenience method that is similar to the following code, except that it offers superior performance:

return String.IsNullOrEmpty(value) || value.Trim().Length == 0;

White-space characters are defined by the Unicode standard. The IsNullOrWhiteSpace method interprets any character that returns a value of true when it is passed to the Char.IsWhiteSpace method as a white-space character.

Short answer:

In common use, space " ", Tab "\t" and newline "\n" are the difference:

string.IsNullOrWhiteSpace("\t"); //true
string.IsNullOrEmpty("\t"); //false

string.IsNullOrWhiteSpace(" "); //true
string.IsNullOrEmpty(" "); //false

string.IsNullOrWhiteSpace("\n"); //true
string.IsNullOrEmpty("\n"); //false

https://dotnetfiddle.net/4hkpKM

also see this answer about: whitespace characters

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Long answer:

There are also a few other white space characters, you probably never used before

https://docs.microsoft.com/en-us/dotnet/api/system.char.iswhitespace

The first method checks if a string is null or a blank string. In your example you can risk a null reference since you are not checking for null before trimming

1- string.IsNullOrEmpty(text.Trim())

The second method checks if a string is null or an arbitrary number of spaces in the string (including a blank string)

2- string .IsNullOrWhiteSpace(text)

The method IsNullOrWhiteSpace covers IsNullOrEmpty, but it also returns true if the string contains white space.

In your concrete example you should use 2) as you run the risk of a null reference exception in approach 1) since you're calling trim on a string that may be null