Introduction
In .NET, a Task represents an asynchronous operation that may or may not return a result. When the result is available, you can use the Result property or the await keyword to retrieve it.
Starting with .NET 5, a new struct called ValueTask was introduced, which is similar to Task but is designed to reduce memory allocations and improve performance.
In this article, we'll explore the differences between Task and ValueTask, and when to use each one.
Task
A Task represents an asynchronous operation that may or may not return a result. It is a reference type, meaning that it is allocated on the heap and is subject to garbage collection.
When you create a Task, you can pass a delegate that represents the operation you want to perform asynchronously. For example:
csharpCopy codeTask.Run(() => DoSomethingAsync());
In the example above, Task.Run creates a new Task that executes the DoSomethingAsync method asynchronously.
When the result is available, you can use the Result property or the await keyword to retrieve it. For example:
csharpCopy codevar result = await Task.Run(() => DoSomethingAsync());
NB - Note that using the Result property blocks the calling thread until the result is available, which can cause performance issues if the operation takes a long time to complete.
ValueTask
A ValueTask is a struct that represents an asynchronous operation that may or may not return a result. Unlike a Task, a ValueTask is a value type, meaning that it is allocated on the stack instead of the heap. This can reduce memory allocations and improve performance, especially for short-lived tasks.
When you create a ValueTask, you can pass a delegate that represents the operation you want to perform asynchronously, just like with a Task. For example:
csharpCopy codeValueTask.Run(() => DoSomethingAsync());
In the example above, ValueTask.Run creates a new ValueTask that executes the DoSomethingAsync method asynchronously.
When the result is available, you can use the Result property or the await keyword to retrieve it, just like with a Task. For example:
csharpCopy codevar result = await ValueTask.Run(() => DoSomethingAsync());
Unlike with a Task, using the Result property of a ValueTask does not block the calling thread. Instead, it returns a completed ValueTask if the result is already available, or it creates a new Task to complete the operation asynchronously.
When to use Task vs. ValueTask
In general, you should use a ValueTask when the operation is expected to complete quickly and is not likely to be awaited multiple times. This is because creating a new Task to complete a ValueTask can be expensive, especially if it happens frequently.
On the other hand, you should use a Task when the operation is expected to take a long time to complete or is likely to be awaited multiple times. This is because a Task can be awaited multiple times without incurring the overhead of creating a new Task each time.
Here are some guidelines to help you decide when to use Task vs. ValueTask:
Use a
Taskif the operation is expected to take more than a few microseconds to complete.Use a
ValueTaskif the operation is expected to complete in a few microseconds or less.
Hope this helped.