How do I use async and await - async-await

Question

So here is the basic of what I am trying to do...
I have create a Web site that has web API 2 so I can do crud operations to that site.
I am trying to create the client side application in VS 2013. I have created a basic Console apps to start the project.
class PortalReposotry
{
private Uri _uri;
public PortalReposotry()
{
_uri = new Uri("http://localhost:21564/");
}
public async Task<CompanyAPI> GetCompany(string companyCode)
{
var client = new HttpClient();
client.BaseAddress = _uri;
client.DefaultRequestHeaders.Accept.Clear();
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
var response = await client.GetAsync(String.Format("api/companies/{0}", companyCode));
CompanyAPI content = await response.Content.ReadAsAsync<CompanyAPI>();
return await Task.Run(() => content);
}
}
class Program
{
static void Main(string[] args)
{
PortalReposotry repo = new PortalReposotry();
CompanyAPI comp = repo.GetCompany("LNCR");
Console.ReadKey();
}
}
I have no Idea why I have to use a lamda expression to return the CompanyAPI object.
All I want returned in the CompanyAPI object not the task it is running on. I am very confused on the threading and why I have to run this under task... it makes where I have to wrap everything into a task.... Which I'll be honest I have no idea how to use or decuple the actual objects from it that I want.
If you can help me out, I could be going the wrong direction all together but this is what I have found so far.

Answer 1

I am very confused on the threading and why I have to run this under task
You don't have to use threading here (the Task.Run is unnecessary). The Task<T> type is a "future" - it represents an asynchronous operation that will have a result value of type T in the future. That's why you need to use tasks with asynchronous code (technically, you could use callbacks instead, but that's much more painful - tasks are easier).
I have created a basic Console apps to start the project.
Asynchronous console apps are a bit weird. You need to block the main thread so the application doesn't exit. This is unnecessary in a real UI client-side app (which I assume your sample project will eventually become). So for now you can just do a hack like this:
static void Main(string[] args)
{
MainAsync().Wait();
}
static async Task MainAsync()
{
PortalReposotry repo = new PortalReposotry();
CompanyAPI comp = await repo.GetCompanyAsync("LNCR");
Console.ReadKey();
}
The call to Wait() should only be done inside a Console app's Main method. You shouldn't ever call it in a UI application.
Since Task.Run isn't needed, you can clean up that method, too:
public async Task<CompanyAPI> GetCompanyAsync(string companyCode)
{
var client = new HttpClient();
client.BaseAddress = _uri;
client.DefaultRequestHeaders.Accept.Clear();
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
var response = await client.GetAsync(String.Format("api/companies/{0}", companyCode));
return await response.Content.ReadAsAsync<CompanyAPI>();
}

Answer 2

in your GetCompany method, the await and Task.Run is unnecessary, you can just return the content.
public async Task<CompanyAPI> GetCompany(string companyCode)
{
var client = new HttpClient();
client.BaseAddress = _uri;
client.DefaultRequestHeaders.Accept.Clear();
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
var response = await client.GetAsync(String.Format("api/companies/{0}", companyCode));
CompanyAPI content = await response.Content.ReadAsAsync<CompanyAPI>();
return content
}
then in your main method you would just call it like so. Disclaimer,
this will make it run synchronously. You can use the ContinueWith method of the Task object to add a "callback" to the task. https://msdn.microsoft.com/en-us/library/system.threading.tasks.task.continuewith(v=vs.110).aspx
CompanyAPI comp = repo.GetCompany("LNCR").Result;