How to Check byte array empty or not

Question

I am downloading the word file for GetSourceAttachment method  When this method returns empty bytes then my byte Attachment array gives an error      Object reference not set instance of object   It gives the error when I check the length of Attachment in if condition    Can any one help me to default initialize the byte array  then check the length   try           byte   Attachment   null            string Extension   string Empty          ClsPortalManager objPortalManager   new ClsPortalManager            Attachment   objPortalManager GetSourceAttachment Convert ToInt32 hdnSourceId Value   out Extension           if  Attachment Length  gt  0  amp  amp  Attachment    null                        DownloadAttachment  Attacment   Attachment  Extension                     else                       ClientScript RegisterStartupScript typeof Page    SymbolError     lt script type  text javascript  gt alert  Attachment is not Uploaded      lt  script gt                             catch

User · Answer

Your check should be   if  Attachment    null   amp  amp  Attachment Length  gt  0    First check if the Attachment is null and then lenght  since you are using  amp  amp  that will cause short-circut evaluation   amp  amp  Operator  C  Reference      The conditional-AND operator   amp  amp   performs a logical-AND of its bool   operands  but only evaluates its second operand if necessary    Previously you had the condition like   Attachment Length  gt  0  amp  amp  Attachment    null   since the first condition is accessing the property Length and if Attachment is null  you end up with the exception  With the modified condition  Attachment    null   amp  amp  Attachment Length  gt  0   it will check for null first and only moves further if Attachment is not null

User · Answer

In Android Studio version 3 4 1  if Attachment    null       code here

User · Answer

Just do  if  Attachment    null   amp  amp  Attachment Length  gt  0    From  amp  amp  Operator     The conditional-AND operator   amp  amp   performs a logical-AND of its bool   operands  but only evaluates its second operand if necessary

User · Answer

You must swap the order of your test  From  if  Attachment Length  gt  0  amp  amp  Attachment    null   To  if  Attachment    null  amp  amp  Attachment Length  gt  0    The first version attempts to dereference Attachment first and therefore throws if it s null  The second version will check for nullness first and only go on to check the length if it s not null  due to  quot boolean short-circuiting quot      EDIT  I come from the future to tell you that with later versions of C  you can use a  quot null conditional operator quot  to simplify the code above to  if  Attachment  Length  gt  0

User · Answer

Now we could also use   if  Attachment    null   amp  amp  Attachment Any      Any   is often easier to understand in a glance for the developer than checking Length     0  Also has very little difference with processing speed

User · Answer

Net V 4 6 OR C    6 0  Try This   if  Attachment  Length  gt  0

[c#] How to Check byte array empty or not?

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