Microsoft design guidelines how to#
Microsoft design guidelines code#

Without a way of cleaning up a HttpClient or HttpClientHandler after its creation - the moment the client goes bad, if it's not recreated then the application will be stuck until recycled.

Microsoft design guidelines how to#

And it opens the door into finding solutions for other problems with the HttpClient such as, how to properly deal with DNS changes after the client has been instantiated. This approach resolves the single instance for the lifetime of the application and still allows for scalability and accessibility from several threads. Example 3: One solution public static GetHttpClientHandler() What then is a good way to both share the HttpClient resources to enable the high scalability and performance while not exhausting system resources but avoiding the problems that come from using the same instance of HttpClient from several threads? One answer is using a shared instance of HttpClientHandler which is passed into an instance of HttpClient and informing the client that it does not own the underlying handler. HttpClient client = new HttpClient(handler) //and we continue to avoid following our recommendations HttpClientHandler handler = new HttpClientHandler() //once again we create a new instance each time this method is called Create an HttpClientHandler object and set to use default credentials Again, looking into the documentation examples we do not have any improved details for handling creating a single instance and re-usability with HttpClient: More Misleading Examples static async Task Main() HttpClientHandler is responsible for managing the underlying connection resources of the HttpClient instances. At this point in the discussion the developer may start to read about the HttpClientHandler class. The developer requires a different solution. Using a single static instance of HttpClient will not fix the situation. For example, one issue that arises using this approach could be that several threads contend for the default headers collection of the same instance of the HttpClient class and create a high CPU condition. This solution may not be the best for applications making multiple calls using the same instance of HttpClient from several threads. Private static readonly HttpClient HttpClient Our next example resolves one part of our recommendations: creating a single instance but fails to advise us on the practical situation the HttpClient is called regularly from many threads Example 2: Solves one problem introduces another public class GoodController : ApiController Underload this may cause resource issues with the application. This breaks the guidance given already as it does not create a single instance once and re-use. Using (HttpClient client = new HttpClient()) Create a New HttpClient object and dispose it when done, so the app doesn't leak resources

Microsoft design guidelines code#

Take for example the following code sample which describes a design pattern which is in fact, not recommend: Example 1: Directly contradicts our published guidance static async Task Main() However, the example provided in the documentation may unintentionally mislead developers into making a poor design choice. The language вЂ instantiated once and re-usedвЂ™ invokes in the developer mind, multiple potential solutions. Below is an example using HttpClient correctly. This will result in SocketException errors. Instantiating an HttpClient class for every request will exhaust the number of sockets available under heavy loads. HttpClient is intended to be instantiated once and re-used throughout the life of an application. Design Pattern Discussion Initial Problems RecommendationsД makes an important observation about HttpClient usage