Difference between IsNullOrEmpty and IsNullOrWhiteSpace in C#

Question

What are differences between these commands in C#

string text= "  ";
1-string.IsNullOrEmpty(text.Trim())

2-string.IsNullOrWhiteSpace(text)

Solution 1

• 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.

Solution 2

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

---

Long answer:

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

• Members of the UnicodeCategory.SpaceSeparator category, which includes the characters SPACE (U+0020), NO-BREAK SPACE (U+00A0), OGHAM SPACE MARK (U+1680), EN QUAD (U+2000), EM QUAD (U+2001), EN SPACE (U+2002), EM SPACE (U+2003), THREE-PER-EM SPACE (U+2004), FOUR-PER-EM SPACE (U+2005), SIX-PER-EM SPACE (U+2006), FIGURE SPACE (U+2007), PUNCTUATION SPACE (U+2008), THIN SPACE (U+2009), HAIR SPACE (U+200A), NARROW NO-BREAK SPACE (U+202F), MEDIUM MATHEMATICAL SPACE (U+205F), and IDEOGRAPHIC SPACE (U+3000).
• Members of the UnicodeCategory.LineSeparator category, which consists solely of the LINE SEPARATOR character (U+2028).
• Members of the UnicodeCategory.ParagraphSeparator category, which consists solely of the PARAGRAPH SEPARATOR character (U+2029).
• The characters CHARACTER TABULATION (U+0009), LINE FEED (U+000A), LINE TABULATION (U+000B), FORM FEED (U+000C), CARRIAGE RETURN (U+000D), and NEXT LINE (U+0085).

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

Solution 3

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 only white space characters.

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

Solution 4

This is implementation of methods after decompiling.

    public static bool IsNullOrEmpty(String value) 
    {
        return (value == null || value.Length == 0); 
    }

    public static bool IsNullOrWhiteSpace(String value) 
    {
        if (value == null) return true; 

        for(int i = 0; i < value.Length; i++) { 
            if(!Char.IsWhiteSpace(value[i])) return false; 
        }

        return true;
    }

So it is obvious that IsNullOrWhiteSpace method also checks if value that is being passed contain white spaces.

Whitespaces refer : https://msdn.microsoft.com/en-us/library/system.char.iswhitespace(v=vs.110).aspx

Solution 5

String.IsNullOrEmpty(string value) returns true if the string is null or empty. For reference an empty string is represented by "" (two double quote characters)

String.IsNullOrWhitespace(string value) returns true if the string is null, empty, or contains only whitespace characters such as a space or tab.

To see what characters count as whitespace consult this link: http://msdn.microsoft.com/en-us/library/t809ektx.aspx

View more solutions

Comments

[ojlovecd]

refer to :msdn.microsoft.com/en-us/library/… and msdn.microsoft.com/en-us/library/…

[samus]

"IsNullOrWhiteSpace covers IsNullOrEmpty" (see TGH answer).

[samus]

What about string.IsNullOrWhiteSpace("") ?

[fubo]

@samusarin no difference dotnetfiddle.net/9uWpvh

[Azimuth]

Your example is not correct since string.IsNullOrEmpty will return true for variable str.

[vibs2006]

@Azimuth I'm not able to understand properly. Can you please create a fiddle on rextester.com or any other C# online Fiddle Tool that you prefer?

[Azimuth]

why should I provide some fiddle? Just replace IsNullOrWhiteSpace with IsNullOrEmpty in your code and run it. It will return true. Thus, your example doesn't show the difference between IsNullOrWhiteSpace and IsNullOrEmpty.

[vibs2006]

sure I'll do that. Thanks @Azimuth for explaining.

[Sachintha Udara]

string.IsNullOrWhiteSpace returns this expression String.IsNullOrEmpty(value) || value.Trim().Length == 0; So, use it in textbox of entry(xamarin) validation handlers

[goldenratio]

with c#6 you can do string.IsNullOrEmpty(text?.Trim()) safely

[Shaiju T]

So its always better to use IsNullOrWhiteSpace than IsNullOrEmpty ?

[Shaiju T]

Nice, : ) How did you decompile to look at the implementation ?

[Ľuboš Pilka]

Using decompiler like dotpeek

[galaxis]

Actually the trimmed string length test will also catch empty strings, so