Why should I use var instead of a type

Question

Possible Duplicate    ReSharper and var       After I have installed ReSharper it demands by warnings  that I use var whenever possible  for example  UnhandledExceptionEventArgs ue    UnhandledExceptionEventArgs  t    ReSharper wants to turn it into  var ue    UnhandledExceptionEventArgs  t    I like the first version better  is there any reason to prefer var  better performance  anything  or is it just a code style

User · Answer

In this case it is just coding style    Use of var is only necessary when dealing with anonymous types  In other situations it s a matter of taste

User · Answer

When you say  by warnings  what exactly do you mean  I ve usually seen it giving a hint that you may want to use var  but nothing as harsh as a warning   There s no performance difference with var - the code is compiled to the same IL  The potential benefit is in readability - if you ve already made the type of the variable crystal clear on the RHS of the assignment  e g  via a cast or a constructor call   where s the benefit of also having it on the LHS  It s a personal preference though   If you don t want R  suggesting the use of var  just change the options  One thing about ReSharper  it s very configurable

User · Answer

As the others have said  there is no difference in the compiled code  IL  when you use either of the following   var x1   new object    object x2   new object    I suppose Resharper warns you because it is  in my opinion  easier to read the first example than the second  Besides  what s the need to repeat the name of the type twice   Consider the following and you ll get what I mean   KeyValuePair lt string  KeyValuePair lt string  int gt  gt  y1   new KeyValuePair lt string  KeyValuePair lt string  int gt  gt   key   new KeyValuePair lt string  int gt   subkey   5      It s way easier to read this instead   var y2   new KeyValuePair lt string  KeyValuePair lt string  int gt  gt   key   new KeyValuePair lt string  int gt   subkey   5

User · Answer

It s really just a coding style  The compiler generates the exact same for both variants   See also here for the performance question    Will using   39 var  39  affect performance

[c#] Why should I use var instead of a type?

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