Implicitly typed local variables

C# language feature:

Implicitly typed local variables

applies to

anonymous types, local variable declarations

benefit

Allows a placeholder for anonymous types, which are often used in query expressions. Additionally, allows simplified declaration of local variables.

how to use

Use the var contextual keyword (instead of a type specifier).

note

Use of var does not hinder type safety. It allows convienient delaration of variables.

example:

        void Use_of_Implicit_Types_Example()
        {
            var x = 5;  // variable x is an int
            var mystring = "test"; // variable mystring is a string

            List<int> ratings = new List<int> { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
            var highratings = from rating in ratings
                              where rating > 7
                              select new { highrating = rating };  // `var` used here to declare and assign a new anonymous type
        }

C# articles

csharp v2 +

Anonymous methods * Co- and Contra-variance for delegates * Delegate inference * Generics * Getter and setter separate accessibility * Iterators * Method group conversions (delegates) * Nullable types * Partials * Static classes *

csharp v3 +

Anonymous types * Auto-Implemented properties * Expression trees * Extension methods * Implicitly typed local variables * Lambda expression * Object and collection initializers * Partial methods * Query expressions *

csharp v4 +

Generic co- and contravariance * Named and optional arguments *

csharp v5 +

Asynchronous methods * Caller info attributes *

csharp v6 +

A note for CSharp 6 and beyond * Allow await in catch and finally blocks * Auto property initializers * Default values for Read-only Auto-properties * Dictionary (index) initializers * Exception filters * Expression-bodied members * Import of static type members into namespace * Null propagator (null-conditional operator, succinct null checking) * String interpolation * nameof operator *

csharp v7 +

Binary literals * Deconstruction * Digit separators * Expression bodied constructors and finalizers * Expression bodied getters and setters * Generalized async return types * Local functions * Out variables * Pattern matching * Ref returns and locals * Tuples *

Code-Sage