Is Asynchronous The Best Way To Go in ASP.NET Core?

6th May 2020

Anyone who has programmed in C# has probably come across keywords such as async or await. And, you may have also come across the Task class. These help you program your C# application. But is there any real benefits using asynchronous in a ASP.NET Core app?

What is Synchronous and Asynchronous?

It’s probably a good time to describe what synchronous and asynchronous is and how the two differ. There are quite a lot of differences between the two.

Synchronous

I’ve taken the example of a fast food restaurant. Below shows a customer requesting their order to the assistant.

Synchronous Example in C# (1)

So that same assistant goes ahead and prepares their burger. Once the burger is ready, the assistant gives it to the customer. But hold on, the customer also wants a portion of fries.

Synchronous Example in C# (2)

So the same assistant goes ahead and prepares their fries. Whilst all this is happening, the line is getting longer and other customers are starting to get impatient.

Synchronous Example in C# (3)

Finally, the customer has all his food items and can go away and thrust their hunger. But now there are three other customers that have joined the line.

Synchronous Example in C# (4)

That’s basically synchronous in a nutshell.

  • A request is received and is allocated to a thread. In our example, this is where the customer requests for their food order to the assistant.
  • That request is handled by the same thread. This is where the same assistant goes ahead and prepares their food order
  • The response is returned by the same thread. This is where the same assistant delivers the food order to the customer.

As you can see, this is simple approach, but quite time consuming. A queue can be formed for intensive tasks. Now, that’s look at the alternative.

Asynchronous

Once again, I’ve taken the example of a fast-food restaurant. The same customer is requesting their order to the assistant.

Asynchronous Example in C# (1)

But rather than the same assistant preparing the order, they delegate the order to their co-workers. And if the customer requests to add to their order, that can also be delegated.

Asynchronous Example in C# (2)

That means that the assistant can serve the next customer whilst the previous customer’s order is being prepared. Once the order is ready, the assistant’s co-workers can deliver the food to the customer.

Asynchronous Example in C# (3)

That’s basically asynchronous in a nutshell.

  • A request is received and is allocated to a thread. In our example, this is where the customer requests for their food order to the assistant.
  • That request is delegated to another thread. This is where the assistant sends the food request to their co-workers.
  • The response is returned. This is where the co-workers delivers the food order to the customer once it’s prepared.

So, we can see some obviously speed advantages with asynchronous. However, there may be a case that there is too much going on for the system to cope.

Asynchronous in ASP.NET Core?

There are some applications where asynchronous is a good approach, such as a desktop application. But what about web applications? Web servers are designed to work asynchronously. If you load a page and open up your browser’s developer tools, you will see that the images and style sheets run in parallel, creating new threads every time. They don’t wait to load one at the time, otherwise you would be there forever.

I’ve put together a little test to see if that’s the case. We throw a number of requests at synchronous and asynchronous methods to see which one performs the quickest. Watch the video below to find out the results.

Learnings

Now, it must be said that JavaScript frameworks or Blazor are probably better running asynchronous. As there is a good chance that you are only going to be reloading parts of the application when making requests, there are some benefits using asynchronous.

But, it’s worth noting to review what parts of your application you are making asynchronous and how it will effect performance. It’s not just the case of changing the return type to Task and adding async and await all over your application. Seeking extra performance this way may have the opposite effect!

David Grace

David Grace

I am a .NET developer, building web applications in .NET Framework and .NET Core with a SQL Server database.

Some of the .NET packages I have used include Entity Framework and MVC.

I've also used many JavaScript frameworks such as React and jQuery, and have experience building CSS in SASS.

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