Generalized async return types

C# language feature:

Generalized async return types

applies to

async return types

benefit

Improve performance by allowing async methods to return ValueTask<TResult>. Previously async types were limited to returning void, Task, Task<T>. Use of Task<T> requires allocating object which hinders performance.

how to use

Specify ValueTask<TResult> as the return type.

important note

To use the ValueTask<TResult>, add NuGet package System.Threading.Tasks.Extensions to your project.

example:

        public async ValueTask<double> Generalized_Async_Return_Types_Example()
        {
            await Task.Delay(100);
            return 3.14;
        }

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