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What is the 'async' and 'await' keywords used for in C#?

Rocky Dada22627-Sep-2023

What are the 'async' and 'await' keywords used for in C#? Also, explain with an example.

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Updated on 05-Oct-2023
Rocky Dada

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Aryan Kumar

Aryan Kumar

05-Oct-2023

In C#, the async and await keywords are used to work with asynchronous programming. They provide a way to write asynchronous code that appears more like synchronous code, making it easier to reason about and manage asynchronous operations. Here's what the async and await keywords are used for in C#:

1. async Keyword:

The async keyword is used to declare a method as asynchronous. An asynchronous method is a method that can execute asynchronously, allowing other code to run in parallel while it waits for an asynchronous operation to complete.

Async methods are typically used for operations that may take time, such as I/O-bound operations (file I/O, network requests) or CPU-bound operations (complex calculations), to avoid blocking the main thread of execution.

Async methods are defined with the async keyword in the method signature, like this:

public async Task MyAsyncMethod()
{
    // Asynchronous code here
}

2. await Keyword:

The await keyword is used within an async method to indicate that a particular operation should be awaited. It tells the compiler to pause the execution of the method until the awaited operation completes. The awaited operation is typically a Task, which represents an asynchronous operation.

When you await a Task, the control returns to the calling method or continues other work until the awaited Task is finished. This allows you to write asynchronous code in a more linear, synchronous-like style.

Here's an example of using await to wait for an asynchronous operation:

public async Task MyAsyncMethod()
{
    // Some synchronous code here
    await SomeAsyncOperation(); // This operation will be awaited
    // More code to run after the awaited operation completes
}

3. Asynchronous Code Execution:

By using async and await, you can write code that performs asynchronous operations without blocking the main thread. This is especially important for applications that require responsiveness and shouldn't freeze while waiting for long-running operations to complete.

Asynchronous programming can improve the scalability and performance of applications by allowing them to handle multiple concurrent tasks efficiently.

4. Exception Handling:

  • async and await also simplify exception handling in asynchronous code. Exceptions that occur in an async method can be caught using standard try-catch blocks as if the code were synchronous. This makes error handling more intuitive.

5. Task-Based Asynchronous Pattern (TAP):

  • async and await are part of the Task-Based Asynchronous Pattern (TAP) in C#. TAP is a recommended approach for asynchronous programming in modern C# applications and libraries.

In summary, async and await keywords in C# are used to write asynchronous code that executes concurrently with other code while providing a more readable and maintainable structure. They are essential for handling asynchronous operations efficiently and improving the responsiveness and performance of C# applications, especially in scenarios involving I/O or long-running tasks.

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