How to initialize var

Question

Can I initialize var with null or some empty value

User · Accepted Answer

C  is a strictly strongly typed language  var was introduced for compile-time type-binding for anonymous types yet you can use var for primitive and custom types that are already known at design time  At runtime there s nothing like var  it is replaced by an actual type that is either a reference type or value type   When you say    var x   null     the compiler cannot resolve this because there s no type bound to null  You can make it like this   string y   null  var x   y    This will work because now x can know its type at compile time that is string in this case

User · Answer

Well  as others have stated  ambiguity in type is the issue  So the answer is no  C  doesn t let that happen because it s a strongly typed language  and it deals only with compile time known types  The compiler could have been designed to infer it as of type object  but the designers chose to avoid the extra complexity  in C  null has no type    One alternative is  var foo   new        anonymous type   Again note that you re initializing to a compile time known type  and at the end its not null  but anonymous object  It s only a few lines shorter than new object    You can only reassign the anonymous type to foo in this one case  which may or may not be desirable    Initializing to null with type not being known is out of question   Unless you re using dynamic   dynamic foo   null    or var foo    dynamic null    overkill   Of course it is pretty useless  unless you want to reassign values to foo variable  You lose intellisense support as well in Visual Studio    Lastly  as others have answered  you can have a specific type declared by casting   var foo    T null    So your options are     initializes to non-null  I like it  cant be reassigned a value of any type var foo   new          initializes to non-null  can be reassigned a value of any type var foo   new object       initializes to null  dangerous and finds least use  can be reassigned a value of any type dynamic foo   null  var foo    dynamic null     initializes to null  more conventional  can be reassigned a value of any type object foo   null     initializes to null  cannot be reassigned a value of any type var foo    T null

User · Answer

Well  I think you can assign it to a new object  Something like    var v   new object

User · Answer

Nope  var needs to be initialized to a type  it can t be null

User · Answer

var just tells the compiler to infer the type you wanted at compile time   it cannot infer from null  though there are cases it could    So  no you are not allowed to do this   When you say  some empty value    if you mean   var s   string Empty     var s         Then yes  you may do that  but not null

User · Answer

Why wouldn t this be possible   var theNameOfTheVar    TheType null    eg   var name    string null    Simple as that

User · Answer

A var cannot be set to null since it needs to be statically typed   var foo   null     compiler goes   Huh  what s that type of foo     However  you can use this construct to work around the issue   var foo    string null     compiler goes   Ah  it s a string  Nice     I don t know for sure  but from what I heard you can also use dynamic instead of var  This does not require static typing   dynamic foo   null  foo    hi     Also  since it was not clear to me from the question if you meant the varkeyword or variables in general  Only references  to classes  and nullable types can be set to null  For instance  you can do this   string s   null     reference SomeClass c   null     reference int  i   null     nullable   But you cannot do this   int i   null     integers cannot contain null

User · Answer

you cannot assign null to a var type   If you assign null the compiler cannot find the variable you wanted in var place   throws error  Cannot assign  lt null gt  to an implicitly-typed local variable    you can try this   var dummy   string null    Here compiler can find the type you want so no problem  You can assign some empty values   var dummy   string Empty    or  var dummy   0

User · Answer

you can t initialise var with null  var needs to be initialised as a type otherwise it cannot be inferred  if you think you need to do this maybe you can post the code it is probable that there is another way to do what you are attempting

User · Answer

This is the way how to intialize value to var variable  var  myVal    dynamic null

User · Answer

Thank you Mr Snake  Found this helpfull for another trick i was looking for     Not enough rep to comment   Shorthand assignment of nullable types  Like this    var someDate    Convert IsDBNull dataRow  SomeDate                          Convert ToDateTime dataRow  SomeDate                           DateTime   null

[c#] How to initialize var?

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