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How to check an empty string in C#

Posted on 2012-08-29
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Last Modified: 2012-08-30
Hi experts
I am trying to check for an empty string but I wonder why the following doesn't work.
  string s = "  "; // two empty spaces.
  bool flag = string.IsNullOrEmpty(s); // gives false.
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Question by:dominicwong
7 Comments
 
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by:Guy Hengel [angelIII / a3]
Guy Hengel [angelIII / a3] earned 800 total points
ID: 38349020
because "  " is not a empty string.

you would need to check with s.Trim(), but then again, if s is null, that would raise a "objectnotset" exception.
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by:Rikin Shah
Rikin Shah earned 100 total points
ID: 38349034
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LVL 45

Assisted Solution

by:AndyAinscow
AndyAinscow earned 200 total points
ID: 38349047
If you require to check often that a string of blank spaces is 'empty' (as angelIII says it is not actually empty) then you might want to create your own string class based on the System.String or a function to do the job for you:

bool IsNullOrEMPTY(String s)
{
  //test for null and return if null

  //trim blank spaces off the ends

  //test if empty and return
}
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LVL 12

Accepted Solution

by:
rajapandian_81 earned 800 total points
ID: 38349048
Hi,

Framework 4.0 has string method called IsNullOrWhiteSpace. It will return true if the specified string is null, empty, or consists only of white-space characters.
string s = "  ";
bool flag = string.IsNullOrWhiteSpace(s);

Open in new window


For older framework you should use
string s = "  ";
bool flag = String.IsNullOrEmpty(s) || s.Trim().Length == 0;

Open in new window

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Assisted Solution

by:AndyAinscow
AndyAinscow earned 200 total points
ID: 38349072
IsNullOrWhitespace - a blank is NOT the only whitespace character.
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Assisted Solution

by:aplusexpert
aplusexpert earned 100 total points
ID: 38349496
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Author Closing Comment

by:dominicwong
ID: 38352606
I forgot to mention that mine is .NET 3.5
Thanks to the prompts responses and help from everyone. I appreciate that.
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