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Dominic Burford - Professional Profile



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I am a professional software engineer and architect with over eighteen years commercial development experience with a strong focus on the design and development of web and mobile applications.

I have experience of architecting scalable, distributed, high volume web applications that are accessible from multiple devices due to their responsive web design, including architecting enterprise service-oriented solutions. I have also developed enterprise mobile applications using Xamarin and Telerik Platform.

I have extensive experience using .NET, ASP.NET, Windows and Web Services, WCF, SQL Server, LINQ and other Microsoft technologies. I am also familiar with HTML, Bootstrap, Javascript (inc. JQuery and Node.js), CSS, XML, JSON, Apache Cordova, KendoUI and many other web and mobile related technologies.

I am enthusiastic about Continuous Integration, Continuous Delivery and Application Life-cycle Management having configured such environments using CruiseControl.NET, TeamCity and Team Foundation Services. I enjoy working in Agile and Test Driven Development (TDD) environments.

Outside of work I have two beautiful daughters. I enjoy cycling, running and taking the dog for long walks. I love listening to music and am a fan of Rush and the Red Hot Chilli Peppers to name a few.

 

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GeneralWriting flexible filters for your data using Predicates Pin
Dominic Burford16-Jul-19 6:11
professionalDominic Burford16-Jul-19 6:11 
GeneralRe: Writing flexible filters for your data using Predicates Pin
Slacker00716-Jul-19 22:09
professionalSlacker00716-Jul-19 22:09 
GeneralRe: Writing flexible filters for your data using Predicates Pin
Dominic Burford17-Jul-19 1:17
professionalDominic Burford17-Jul-19 1:17 
GeneralBlocking Asynchronous Code Pin
Dominic Burford4-Jul-19 22:11
professionalDominic Burford4-Jul-19 22:11 
Following on from a previous article[^] I wrote as an introduction to writing asynchronous code with .NET, I want to describe a common problem I see developers making when they begin writing asynchronous code beyond the basics. A common mistake developers make when they first start writing asynchronous code using the .NET Framework, is to write blocking asynchronous code. I've seen this problem on Stackoverflow and with developers I have worked with directly (both junior and senior).

Rather than try to explain the problem, I'll give some example code that should hopefully highlight the problem. Here's an ASP.NET Web API RESTful service being invoked from a client application.

The back-end service code is taken from one of our RESTful services that returns vehicle telemetry to a client application. For the purposes of clarity, I have omitted all logging, error checking and authentication code.
public async Task<string> Get(string subscriber, string trackertype)
{
  var response = await this.GetData(subscriber, trackertype);
  return response;
}
And here is a client that invokes the RESTful service. In this example the client is a unit test.
[TestMethod]
public async Task GetVehicleTests()
{
  //Arrange
  TrackerController controller = new TrackerController();

  //Act
  string subscriber = "testsubscriber";
  string vehicle = "testvehicle";    
  var response = controller.Get(subscriber, vehicle);

  //Assert
  Assert.IsNotNull(response);
  Assert.IsNotNull(response.Result.ToString());
}
The above unit test code will deadlock. Remember, that after you await a Task, when the method continues it will continue in a context.

1. The unit test calls the Get() RESTful service (within the ASP.NET Web API context).
2. The Get() method in turn calls the GetData() method.
3. The GetData() method returns an incomplete Task indicating that the Get() method has not yet completed (with the same context).
4. The Get() method awaits the Task returned by the GetData() method (the context is saved and can be re-instated later).
5. The unit test synchronously blocks on the Task returned by the Get() method which in turn blocks the context thread.
6. Eventually the Get() method will complete. This in turn completes the Task that was returned by the GetData() method.
7. The continuation for Get() is now ready to run, and it waits for the context to be available to allow it to execute in the context.
8. Deadlock. The unit test is blocking the context thread, waiting for the Get() method to complete, and GetData() is waiting for the context to be available so it can complete.

How can this situation be prevented? Simple. Don't block on Tasks.

1. Use async all the way down
2. Make (careful) use of ConfigureAwait(false)

For the first suggestion, awaitable code should always be executed asynchronously. So given the example code here, the unit test was not correctly awaiting the result from the RESTful service. The unit test code should be modified as follows.
[TestMethod]
public async Task GetVehicleTests()
{
  //Arrange
  TrackerController controller = new TrackerController();

  //Act
  string subscriber = "testsubscriber";
  string vehicle = "testvehicle";    
  var response = await controller.Get(subscriber, vehicle);

  //Assert
  Assert.IsNotNull(response);
  Assert.IsNotNull(response.ToString());
}
Like a handshake, whenever you have an await at one end of a service call, you should have async at the other.

The use of ConfigureAwait(false) is slightly more complicated. When an incomplete Task is awaited, the current context is captured to allow the method to be resumed when the task eventually completes e.g. after the await keyword. The context is null if invoked from a thread that is NOT the UI thread. Otherwise it returns the UI specific context depending on the specific platform you are using e.g. ASP.NET, WinForm etc). It is this constant context switching between UI thread context and worker thread context that can cause performance issues. These issues may lead to a less responsive application, especially as the amount of async code grows (due to the increased volume of context-switching). Yet this is exactly what we are trying to solve by using asynchronous code in the first place.

There are a few rules to bear in mind when using ConfigureAwait(false)

- The UI should always be updated on the UI thread i.e. you should not use ConfigureAwait(false) when the code immediately after the await updates the UI
- Each async method has its own context which means that the calling methods are not affected by ConfigureAwait()
- ConfigureAwait can return back on the original thread if the awaited task completes immediately or is already completed.

A good rule of thumb would be to separate out the context-dependent code from the context-free code. The goal is to reduce the amount of context-dependent code (which can typically include event handlers).

We can modify the Get() RESTful service as follows.
public async Task<string> Get(string subscriber, string trackertype)
{
  var response = await this.GetData(subscriber, trackertype).ConfigureAwait(false);
  return response;
}
Deadlocks such as this arise from not fully understanding asynchronous code, and the developer ends up with code that is partly synchronous and partly asynchronous.

By following the suggestions in this article, you should see performance gains in your own code, as well as better understanding how asynchronous code works under the hood.
"There are two ways of constructing a software design: One way is to make it so simple that there are obviously no deficiencies, and the other way is to make it so complicated that there are no obvious deficiencies. The first method is far more difficult." - C.A.R. Hoare

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GeneralDesigning and implementing flexible RESTful services Pin
Dominic Burford14-Jun-19 0:50
professionalDominic Burford14-Jun-19 0:50 
GeneralWriting asynchronous code with .NET Pin
Dominic Burford10-Jun-19 3:34
professionalDominic Burford10-Jun-19 3:34 
GeneralWeird Minification Behaviour in ASP.NET Core Pin
Dominic Burford28-May-19 3:54
professionalDominic Burford28-May-19 3:54 
GeneralThe Importance of Structure and Dilligence Pin
Dominic Burford24-May-19 6:14
professionalDominic Burford24-May-19 6:14 
GeneralWhen should you rewrite that legacy application? Pin
Dominic Burford22-May-19 0:03
professionalDominic Burford22-May-19 0:03 
GeneralImproving Your SQL Stored Procedures Pin
Dominic Burford2-May-19 5:47
professionalDominic Burford2-May-19 5:47 
GeneralPassing a list of items to a SQL stored procedure Pin
Dominic Burford27-Mar-19 0:55
professionalDominic Burford27-Mar-19 0:55 
GeneralSoftware development is like plumbing Pin
Dominic Burford8-Mar-19 5:12
professionalDominic Burford8-Mar-19 5:12 
GeneralVersioning a .NET Core 2.2 application Pin
Dominic Burford7-Mar-19 5:04
professionalDominic Burford7-Mar-19 5:04 
GeneralUsing tags with push notifications from Azure Notification Hub Pin
Dominic Burford17-Feb-19 23:21
professionalDominic Burford17-Feb-19 23:21 
GeneralSending Push Notifications with Azure Notification Hub Pin
Dominic Burford25-Jan-19 4:34
professionalDominic Burford25-Jan-19 4:34 
GeneralUnit testing a Xamarin Forms mobile app Pin
Dominic Burford13-Jan-19 21:59
professionalDominic Burford13-Jan-19 21:59 
GeneralApple development sucks Pin
Dominic Burford8-Jan-19 1:09
professionalDominic Burford8-Jan-19 1:09 
GeneralBut the tech giants are private companies Pin
Dominic Burford19-Dec-18 5:31
professionalDominic Burford19-Dec-18 5:31 
GeneralThe latest version of our app nears completion Pin
Dominic Burford7-Dec-18 2:21
professionalDominic Burford7-Dec-18 2:21 
GeneralIs Silicon Valley a force for good? Pin
Dominic Burford27-Nov-18 21:57
professionalDominic Burford27-Nov-18 21:57 
GeneralUsing Javascript to retrieve values from a Xamarin Forms WebView Pin
Dominic Burford27-Nov-18 5:01
professionalDominic Burford27-Nov-18 5:01 
GeneralUsing the MVVM pattern with a Xamarin Forms mobile app Pin
Dominic Burford21-Nov-18 1:13
professionalDominic Burford21-Nov-18 1:13 
GeneralConsuming a private nuget feed in an Azure DevOps build pipeline Pin
Dominic Burford2-Nov-18 6:55
professionalDominic Burford2-Nov-18 6:55 
GeneralBuild a Xamarin.Forms iOS mobile app using Azure DevOps Pin
Dominic Burford8-Oct-18 23:38
professionalDominic Burford8-Oct-18 23:38 
GeneralDeploy a Mobile app to Azure using Azure DevOps Pin
Dominic Burford21-Sep-18 5:30
professionalDominic Burford21-Sep-18 5:30 

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