execute next statement only when awaited method complete its execution

trishelwood

I am calling API using HTTPClient PostAsync() method. This postasync method is in async task.
I am calling this task from my ViewModel using await keyword.
Like this

public ProfileViewModel() // Constructor { ABC(); } async void ABC() { IsBusy = true; await GetData(); Task.Delay(2000); App.IsAwaiting = true; } async Task<bool> GetData() { IsBusy = true; string response = await CallAPI.getFullProfile("1"); // CallAPI is a class where I created method to get profile of user using PostAsync method. App.IsAwaiting = true; App.Profile = JsonConvert.DeserializeObject<ProfileModel>(response); IsBusy = false; return true; }

Here when I call getFullProfile because of await keyword it goes to constructor's ending brackets. But I want to fill data after calling API.

So, when I try to debug for the first time, I don't get data but when I run my app second time, it shows data because in that time awaited method completes its execution.

Is there any way so that I compiler wait until data from API comes and then execute next statement ?

I tried to delay task by using Task.Delay() but it doesn't work.

kentucker

You should use await Task.Delay(2000) if you want it to pause. Never ever use async void outside of an event handler. You should change ABC to return a Task or Task of bool

https://msdn.microsoft.com/en-us/magazine/jj991977.aspx?f=255&MSPPError=-2147217396

JimBennett

Why would you want your view model's constructor to wait for the data? Usually view models are created on the UI thread, and you won;dn't want that thread to block whilst it downloads data (which could take a looooong time on a slow connection, or if the call fails crash your app).

It would be better to not load the data in the constructor, but instead have a different async method or command you call when your view is loaded, maybe showing a progress spinner whilst the data loads.

trishelwood

Thanks for commenting @kentucker and @JimBennett. Now I am calling this method in different task when my app starts. and it is working fine for me.

I am wondering why this idea not came to my mind before posting this question. Sorry for taking your time.

Thank you.