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

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If your string  In your case the variable text  could be null this would make a big Difference   1-string IsNullOrEmpty text Trim      --  EXCEPTION since your calling a mthode of a null object  2-string IsNullOrWhiteSpace text   This would work fine since the null issue is beeing checked internally  To provide the same behaviour using the 1st Option you would have to check somehow if its not null first then use the trim   method   if   text    null   amp  amp  string IsNullOrEmpty text Trim

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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

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Performance Test  just in case anyone is wondering  in a stopwatch test comparing  if nopass Trim   Length   0   if   string IsNullOrWhiteSpace nopass        these were the results   Trim-Length with empty value   15  Trim-Length with not empty value   52    IsNullOrWhiteSpace with empty value   11  IsNullOrWhiteSpace with not empty value   12

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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

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

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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  lt  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

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string isNullOrWhiteSpace text  should be used in most cases as it also includes a blank string    using System  using System Collections Generic  using System Linq  using System Text RegularExpressions  namespace Rextester       public class Program               public static void Main string   args                          Your code goes here             var str                    Console WriteLine string IsNullOrWhiteSpace str                                       It returns True

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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

[c#] Difference between IsNullOrEmpty and IsNullOrWhiteSpace in C#

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