GetStringAsync() Method in HttpClient Class

C# Tutorials - Herong's Tutorial Examples

∟GetStringAsync() Method in HttpClient Class

A quick introduction is provided on the System.Net.Http.HttpClient class and System.Threading.Tasks.Task<T> class, which can be used to play with asynchronous operations.

To practice the Async feature of C# 5, we can use the System.Net.Http.HttpClient class. Here is some basic information about the HttpClient class.

System.Net.Http.HttpClient is a .NET Framework class that allows us to send HTTP requests to remote Web sites and receive HTTP responses in asynchronous operations. Here are some basic methods supported in the HttpClient class:

HttpClient() - Method to construct a new HttpClient object.
Dispose() - Method to release and dispose resources of this HttpClient object.
GetAsync(String) - Method to send a GET request to the specified URI as an asynchronous operation. It returns immediately with new running task: System.Threading.Tasks.Task<HttpResponseMessage>. When the task is completed, you will get an object of HttpResponseMessage representing the entire HTTP response.
GetStringAsync(String) - Method to send a GET request to the specified URI as an asynchronous operation. It returns immediately with new running task: System.Threading.Tasks.Task<string>. When the task is completed, you will get a string representing the HTTP response body.
GetByteArrayAsync(String) - Method to send a GET request to the specified URI as an asynchronous operation. It returns immediately with new running task: System.Threading.Tasks.Task<byte[]>. When the task is completed, you will get a byte array representing the HTTP response body.

As you can see, these Get*Async() methods return a generic class object, System.Threading.Tasks.Task<T>. So we need to learn some details of the Task<T> class.

System.Threading.Tasks.Task<T> a system class representing an asynchronous operation that returns a result when the operation is completed. Here are some basic properties and methods supported in the Task<T> class:

Task<T>(Func<T>) - Method to construct a new Task<T> object with the specified function, which should return a value of type T. When a new Task<T> object is created, .NET Framework will start a new thread to execute the specified function.
Wait(time) - Method to wait for the specified time in milliseconds or until the task is completed. If the task is completed within the wait time, it returns true. Otherwise, it returns false.
Status - Property to get the status of this Task<T>. Possible status code are: Created, Running, RanToCompletion, Canceled, etc.
Result - Property to get the result, type T, of this Task<T>. The get accessor will wait until the task is completed.

With these two classes, we can start to play with asynchronous operations with GetStringAsync(String) method provided in the HttpClient class. See the next tutorial for examples.