Xamarin Async and Await: UI thread is getting blocked - web-services

Question

I have this architecture in my project and sometimes UI thread is getting blocked, can someone please explain what is happening with the below code. Thanks
I am making a service call asyncronously from xamarin.forms viewmodel
Following is the flow
View--->ViewModel---ClassA--->ClassB--Make a service call from here
Code
Scenario 1
public partial class HomePage : ContentPage
{
private HomeVM model;
public HomePage()
{
InitializeComponent();
model = new HomeVM();
model.MainText = ReturnBool().Result;
this.BindingContext = model;
}
public async Task<string> ReturnBool()
{
IsBusy = true;
var r = await new WS().ReturnBool();
IsBusy = false;---------------------------------------Not hitting the breakpoint here
return r;
}
}
public interface IWS
{
Task<string> ReturnBool();
}
public class WS : IWS
{
public Task<string> ReturnBool()
{
return ServiceOperations.ReturnBool();
}
}
internal class ServiceOperations
{
public async static Task<string> ReturnBool()
{
var uri = new Uri(string.Format("http://testmyapi.azurewebsites.net/", string.Empty));
try
{
HttpClient client = new HttpClient();
client.BaseAddress = uri;
HttpResponseMessage response = null;
response = await client.GetAsync("/api/Values/Get");
if (response.IsSuccessStatusCode)
{
var content = await response.Content.ReadAsStringAsync();
string str = JsonConvert.DeserializeObject<string>(content);
return str;
}
else {
return null;
}
}
catch (Exception)
{
return null;
}
}
}
Scenario 2
public partial class HomePage : ContentPage
{
private HomeVM model;
public HomePage()
{
InitializeComponent();
model = new HomeVM();
this.BindingContext = model;
}
}
public class HomeVM : BaseVM
{
private string mainText;
public string MainText
{
get { return mainText; }
set
{
mainText = value;
RaisePropertyChanged("MainText");
}
}
public HomeVM()
{
MainText = ReturnBool().Result;
}
public async Task<string> ReturnBool()
{
IsBusy = true;
var r = await new WS().ReturnBool();
IsBusy = false;---------------------------------------Not hitting the breakpoint here
return r;
}
}
public interface IWS
{
Task<string> ReturnBool();
}
public class WS : IWS
{
public Task<string> ReturnBool()
{
return ServiceOperations.ReturnBool();
}
}
internal class ServiceOperations
{
public async static Task<string> ReturnBool()
{
var uri = new Uri(string.Format("http://testmyapi.azurewebsites.net/", string.Empty));
try
{
HttpClient client = new HttpClient();
client.BaseAddress = uri;
HttpResponseMessage response = null;
response = await client.GetAsync("/api/Values/Get");
if (response.IsSuccessStatusCode)
{
var content = await response.Content.ReadAsStringAsync();
string str = JsonConvert.DeserializeObject<string>(content);
return str;
}
else {
return null;
}
}
catch (Exception)
{
return null;
}
}
}

Answer 1

You are using ReturnBool().Result in the constructor. The return call will block your UI thread. Move that code to the controller action methods without using ".Result" part. Ensure that the methods are async and always return a Task.