无法在Xamarin android的Portable类库中使用wcf服务POST方法

Question

I am consuming wcf webservices(POST method) in Portable class library in visual studio for xamarin android.App is getting crash in POST method.Below is my code

IN PCL

Class1.cs

namespace XamarinServiceCall
{
    public sealed class Class1 : IRestService
    {

        public async Task<string> GetData(UserModel model)
        {
            using (var client = new HttpClient())
            {
                var content = new StringContent(JsonConvert.SerializeObject(model), Encoding.UTF8, "application/json");

                var result = await client.PostAsync("http://xamarin-rest-service/LoginService/ValidateLogin", content);
                return await result.Content.ReadAsStringAsync();

            }
        }
    }
}

IRestService.cs

namespace XamarinServiceCall
{
    public interface IRestService
    {
        Task<string> GetData(UserModel model);
    }
}

UserModel.cs

public class UserModel
    {

        public string loginFrom { get; set; }

        public string domainName { get; set; }
        public string userName { get; set; }
        public string password { get; set; }

        //I get response of below parameters
        public int DomainType { get; set; }
        public string FirstName { get; set; }

        public int Status { get; set; }
        public int UserId { get; set; }
      }

In Xamarin Android APp

MainActivity.cs

namespace ServiceSample
{
    [Activity(Label = "LayoutSample", MainLauncher = true, Icon = "@drawable/icon")]
    public class MainActivity : Activity
    {
            protected async override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);

            // Set our view from the "main" layout resource
            SetContentView(Resource.Layout.Main);

            // Get our button from the layout resource,
            // and attach an event to it
            Button button = FindViewById<Button>(Resource.Id.MyButton);

            XamarinServiceCall.Class1 serviceClass = new XamarinServiceCall.Class1();
           var model = new XamarinServiceCall.UserModel { domainName = "domainname" ,userName = "username" , password = "password" ,loginFrom = "App" };

            var result = await serviceClass.GetData(model);
            button.Text = "get call says: " + result;

        }
    }
}

Postman Response:

When i debug i get this response in result variable.

When i point to postAsync Function it shows me Expression is not valid

Answer 1

You should not try to perform any significant work, like calling your web service, inside OnCreate function of MainActivity.

And of course, you should not make it async and make asynchronous calls inside it. Please check Xamarin's examples.

Generally, in OnCreate you can make some initialization and then call LoadApplication for your Application class (which you can define in PCL project).