C# Programming/Keywords/var

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The var keyword can be used in place of a type when declaring a variable to allow the compiler to infer the type of the variable. This feature can be used to shorten variable declarations, especially when instantiating generic types, and is even necessary with LINQ expressions (since queries may generate very complex types).

The following:

int num = 123;
string str = "asdf";
Dictionary<int, string> dict = new Dictionary<int, string>();

is equivalent to:

var num = 123;
var str = "asdf";
var dict = new Dictionary<int, string>();

var does not create a "variant" type; the type is simply inferred by the compiler. In situations where the type cannot be inferred, the compiler generates an error:

var str; // no assignment, can't infer type

void Function(var arg1, var arg2) // can't infer type

C# Keywords
abstract as base bool break
byte case catch char checked
class const continue decimal default
delegate do double else enum
event explicit extern false finally
fixed float for foreach
goto if implicit in int
interface internal is lock long
namespace new null object operator
out override params private protected
public readonly ref return sbyte
sealed short sizeof stackalloc
static string struct switch this
throw true try typeof uint
ulong unchecked unsafe ushort using
var virtual void volatile while
Special C# Identifiers
add alias get global partial
remove set value where yield

Note: Var is not a keyword