why we can not use var as a parameter in a function in c#

Question

Sujeet Suman · Answer

Dev "VAR" is compile time thing where as "FUNCTION PARAMETER" is runtime thing. That's why we can not use var as a parameter in a function in c#.

Sujeet Suman · Answer

Thanks Dev to accepting my answer.

Upendra Pratap Shahi · Answer

I've got an error when type public void GetData ( var name="dev" ){} var namespace or assembly not found.

Upendra Pratap Shahi · Answer

Variables declared with var are implicitly but statically typed. basicly var is compiled time and parameter send to function is run time.

Dev sharma · Answer

Hi upendra, As per you comment. Because ' var ' type wants initialization at declaration time while in function we send parameter value and ' var ' type is not define for parameter in function definition while we get this in function body. if i do this like public void GetData ( var name="dev" ){} what you will say

Upendra Pratap Shahi · Answer

Hello Dev sharma, in function definition var type is not defined as a parameter so you can't use this as parameter. Because ' var ' type wants initialization at declaration time while in function we send parameter value and ' var ' type is not define for parameter in function definition while we get this in function body. if helpful accept the answer

Bharath Peggem · Answer

Hi, there is not auto data type conversion in c# for var. so you can not declare paramater value. “Var” keyword defines data type statically see the below link. http://www.dotnetfunda.com/articles/show/1567/what-is-the-use-of-var-keyword-in-csharp

Dev sharma · Answer

Hi Bharath Peggem, My question is why we cannot use var as a parameter in a function in c#

Bharath Peggem · Answer

Hi , “Var” Keyword = Var keyword is an implicit way of defining DataTypes. Implicit means indirect way of defining variable types. “Var” keyword defines data type statically and not on runtime. var i =123; // it is int value i = "abc" // it is string value cannot implicitly convert type ‘string’ to ‘int’ as the variable “i” is declared . its helpfull accept my answer

Dev sharma · Answer

Hi bhushan, check this. public void fun(int i=0,var k=12) { var f = 12; } here f and k 's both initilization is same and so i am asking. now i on same question why we cannot use it as a parameter.

Bhushan Bhasme · Answer

You are not defining any datatype...its var..so it wont be able to identify which datatype is this...though you have given it in double quotes..it wont consider it as string..which datatype is to be consider that info you are not giving..so it will throw you error

Dev sharma · Answer

Hi sanjay , I know we cannot but that is question why????

Sanjay Sabariya · Answer

i'm saying that you can not use as a var keyword as a variable name.

Dev sharma · Answer

Hi bhushan, I know it will throw error but as per your comment if i have write this public void GetData ( var name="dev" ){} as per your compiler will not know but here i am defining datatype also so why error should occur

Bhushan Bhasme · Answer

hi dev, It will through you error. beacuse compiler wont be able to decide the datatype of the variable at compile time..if you use it at scope of function as local variable then it wont throw any error.. but as function parameter compiler wont be able to deciade the datatype of that prameter is it string/int or any other..so it willthrow you error.

Dev sharma · Answer

Hi Bhushan Bhasme, what you would say about it if i use it as. public void GetData ( var name="dev" ){}

Dev sharma · Answer

this is not correct answer Sanjay Sabariya becuase params also keyword but we can use it as a parameter

Sanjay Sabariya · Answer

short answer : var is keyword. so we can not use as variable name.

Bhushan Bhasme · Answer

Hi dev, Var Is Implicitly typed Keyword.. 'var' is just a keyword that tells the compiler to 'analyse whatever comes next to find out the type'. This is done during compilation, not runtime. While Assigning The Variaveble To var,Compiler gets information of datatype at compile time... int x=10; var a=x; so compiler get info that of which datatype is assigned to var . but while passing the variable to function compiler do not get actual info that variable of which datatype is passed to function... if You want to use like var then you can use public void GetData ( dynamic name ){} Hope this will help you

Harshad Pansuriya · Answer

http://blogs.msdn.com/ericlippert/archive/2009/01/26/why-no-var-on-fields.aspx In summary, the main problem is that it would have required a major re-architecture of the C# compiler to do so. Declarations are currently processed in a single pass manner. This would require multiple passes because of the ability to form cycles between inferred variables. VB.net has roughly the same problem.

why we can not use var as a parameter in a function in c#

Answers (20)