IsNothing versus Is Nothing

Question

Does anyone here use VB NET and have a strong preference for or against using IsNothing as opposed to Is Nothing  for example  If IsNothing anObject  or If anObject Is Nothing       If so  why   EDIT  If you think they re both equally acceptable  do you think it s best to pick one and stick with it  or is it OK to mix them

User · Answer

I m leaning towards the  quot Is Nothing quot  alternative  primarily because it seems more OO  Surely Visual Basic ain t got the Ain t keyword

User · Answer

You should absolutely avoid using IsNothing    Here are 4 reasons from the article IsNothing   VS Is Nothing   Most importantly  IsNothing object  has everything passed to it as an object  even value types   Since value types cannot be Nothing  it   s a completely wasted check  Take the following example     Dim i As Integer If IsNothing i  Then      Do something  End If   This will compile and run fine  whereas this   Dim i As Integer If i Is Nothing Then         Do something  End If   Will not compile  instead the compiler will raise the error       Is  operator does not accept operands of type  Integer     Operands must be reference or nullable types   IsNothing object  is actually part of part of the Microsoft VisualBasic dll  This is undesirable as you have an unneeded dependency on the VisualBasic library   Its slow - 33 76  slower in fact  over 1000000000 iterations   Perhaps personal preference  but IsNothing   reads like a Yoda Condition   When you look at a variable you re checking it s state  with it as the subject of your investigation      i e   does it do x  --- NOT Is xing a property of it     So I think If a IsNot Nothing reads better than If Not IsNothing a

User · Answer

I agree with  Is Nothing    As stated above  it s easy to negate with  IsNot Nothing     I find this easier to read     If printDialog IsNot Nothing Then      blah End If   than this     If Not obj Is Nothing Then      blah End If

User · Answer

VB is full of things like that trying to make it both  quot like English quot  and comfortable for people who are used to languages that use    and    a lot  And on the other side  as you already probably know  most of the time you can use    with function calls if you want to  but don t have to  I prefer IsNothing      but I use C and C   so that s just what is comfortable   And I think it s more readable   But go with whatever feels more comfortable to you

User · Answer

If you take a look at the MSIL as it s being executed you ll see that it doesn t compile down to the exact same code  When you use IsNothing   it actually makes a call to that method as opposed to just evaluating the expression    The reason I would tend to lean towards using  Is Nothing  is when I m negating it becomes  IsNot Nothing  rather than  Not IsNothing object   which I personally feel looks more readable

User · Answer

Is Nothing requires an object that has been assigned to the value Nothing  IsNothing   can take any variable that has not been initialized  including of numeric type  This is useful for example when testing if an optional parameter has been passed

User · Answer

I initially used IsNothing but I ve been moving towards using Is Nothing in newer projects  mainly for readability  The only time I stick with IsNothing is if I m maintaining code where that s used throughout and I want to stay consistent

User · Answer

I find that Patrick Steele answered this question best on his blog  Avoiding IsNothing    I did not copy any of his answer here  to ensure Patrick Steele get s credit for his post  But I do think if you re trying to decide whether to use Is Nothing or IsNothing you should read his post  I think you ll agree that Is Nothing is the best choice   Edit - VoteCoffe s comment here  Partial article contents  After reviewing more code I found out another reason you should avoid this  It accepts value types  Obviously  since IsNothing   is a function that accepts an  object   you can pass anything you want to it  If it s a value type   NET will box it up into an object and pass it to IsNothing -- which will always return false on a boxed value  The VB NET compiler will check the  Is Nothing  style syntax and won t compile if you attempt to do an  Is Nothing  on a value type  But the IsNothing   function compiles without complaints  -PSteele     VoteCoffee

[vb.net] IsNothing versus Is Nothing

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