C#: ModernHttpClient, You're referencing the Portable version in your App - you need to reference the platform (iOS/Android) version

Question

I'm using ModernHttpClient library and I'm to trying to get the Cookies from the httpClient's response

public static async Task<String> loginUser()
{
    var values = new List<KeyValuePair<string, string>>
    {
        new KeyValuePair<string, string>("username", "*****"),
        new KeyValuePair<string, string>("password", "*****"),
    };
    NativeCookieHandler cookieHandler = new NativeCookieHandler();
    NativeMessageHandler messageHandler = new NativeMessageHandler(false, false, cookieHandler);
    var httpClient = new HttpClient(messageHandler);

    var response = await httpClient.PostAsync(RestApiPaths.LOGIN, new FormUrlEncodedContent(values));

    response.EnsureSuccessStatusCode();
    String resultString = await response.Content.ReadAsStringAsync();
    System.Diagnostics.Debug.WriteLine("resultString: " + resultString);
    IEnumerable<Cookie> responseCookies = cookieHandler.Cookies;
    Cookie mCookie = responseCookies.FirstOrDefault();
    RestApiPaths.mCookie = mCookie;
    return resultString;

}

But the below line is giving error:

IEnumerable<Cookie> responseCookies = cookieHandler.Cookies;

Error:

MonoDroid] UNHANDLED EXCEPTION:
[MonoDroid] System.Exception: You're referencing the Portable version in your App - you need to reference the platform (iOS/Android) version
[MonoDroid]   at Gogch.MyClass+<loginUser>c__async0.MoveNext () <0x9e0d9e08 + 0x004b8> in <filename unknown>:0 
[MonoDroid] --- End of stack trace from previous location where exception was thrown ---
[MonoDroid]   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () <0x9d3a3670 + 0x00024> in <filename unknown>:0 
[MonoDroid]   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) <0x9d3a2ff8 + 0x000bb> in <filename unknown>:0 
[MonoDroid]   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) <0x9d3a2dd0 + 0x0008b> in <filename unknown>:0 
[MonoDroid]   at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) <0x9d6ecaa8 + 0x0003f> in <filename unknown>:0 
[MonoDroid]   at System.Runtime.CompilerServices.TaskAwaiter`1[TResult].GetResult () <0xa1f0fa18 + 0x0001b> in <filename unknown>:0 
[MonoDroid]   at Gogch.Droid.MainActivity+<button_OnClick>c__async0.MoveNext () <0xaf58c608 + 0x00137> in <filename unknown>:0 
[MonoDroid] --- End of stack trace from previous location where exception was thrown ---
[MonoDroid]   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () <0x9d3a3670 + 0x00024> in <filename unknown>:0 
[MonoDroid]   at System.Runtime.CompilerServices.AsyncMethodBuilderCore.<ThrowAsync>m__0 (System.Object state) <0x9d3a4488 + 0x0003f> in <filename unknown>:0 
[MonoDroid]   at Android.App.SyncContext+<Post>c__AnonStorey0.<>m__0 () <0xa1f0f968 + 0x00027> in <filename unknown>:0 
[MonoDroid]   at Java.Lang.Thread+RunnableImplementor.Run () <0xa1f0f7b8 + 0x0003f> in <filename unknown>:0 
[MonoDroid]   at Java.Lang.IRunnableInvoker.n_Run (IntPtr jnienv, IntPtr native__this) <0xa1f0f710 + 0x0003f> in <filename unknown>:0 
[MonoDroid]   at (wrapper dynamic-method) System.Object:ba036dc5-deef-4850-b986-e1e85c84e6de (intptr,intptr)
[art] JNI RegisterNativeMethods: attempt to register 0 native methods for android.runtime.JavaProxyThrowable
[AndroidRuntime] Shutting down VM
[AndroidRuntime] FATAL EXCEPTION: main
[AndroidRuntime] Process: com.cinch.gogch, PID: 18910
[AndroidRuntime] java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
[AndroidRuntime]    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
[AndroidRuntime] Caused by: java.lang.reflect.InvocationTargetException
[AndroidRuntime]    at java.lang.reflect.Method.invoke(Native Method)
[AndroidRuntime]    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:728)
[AndroidRuntime]    ... 1 more
[AndroidRuntime] Caused by: android.runtime.JavaProxyThrowable: System.Exception: You're referencing the Portable version in your App - you need to reference the platform (iOS/Android) version
[AndroidRuntime]   at Gogch.MyClass+<loginUser>c__async0.MoveNext () <0x9e0d9e08 + 0x004b8> in <filename unknown>:0 
[AndroidRuntime] --- End of stack trace from previous location where exception was thrown ---
[AndroidRuntime]   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () <0x9d3a3670 + 0x00024> in <filename unknown>:0 
[AndroidRuntime]   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) <0x9d3a2ff8 + 0x000bb> in <filename unknown>:0 
[AndroidRuntime]   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) <0x9d3a2dd0 + 0x0008b> in <filename unknown>:0 
[AndroidRuntime]   at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) <0x9d6ecaa8 + 0x0003f> in <filename unknown>:0 
[AndroidRuntime]   at System.Runtime.CompilerServices.TaskAwaiter`1[TResult].GetResult () <0xa1f0fa18 + 0x0001b> in <filename unknown>:0 
[AndroidRuntime]   at Gogch.Droid.MainActivity+<button_OnClick>c__async0.MoveNext () <0xaf58c608 + 0x00137> in <filename unknown>:0 
[AndroidRuntime] --- End of stack trace from previous location where exception was thrown ---
[AndroidRuntime]   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () <0x9d3a3670 + 0x00024> in <filename unknown>:0 
[AndroidRuntime]   at System.Runtime.CompilerServices.AsyncMethodBuilderCore.<ThrowAsync>m__0 (System.Object state) <0x9d3a4488 + 0x0003f> in <filename unknown>:0 
[AndroidRuntime]   at Android.App.SyncContext+<Post>c__AnonStorey0.<>m__0 () <0xa1f0f968 + 0x00027> in <filename unknown>:0 
[AndroidRuntime]   at Java.Lang.Thread+RunnableImplementor.Run () <0xa1f0f7b8 + 0x0003f> in <filename unknown>:0 
[AndroidRuntime]   at Java.Lang.IRunnableInvoker.n_Run (IntPtr jnienv, IntPtr native__this) <0xa1f0f710 + 0x0003f> in <filename unknown>:0 
[AndroidRuntime]   at (wrapper dynamic-method) System.Object:ba036dc5-deef-4850-b986-e1e85c84e6de (intptr,intptr)
[AndroidRuntime]    at mono.java.lang.RunnableImplementor.n_run(Native Method)
[AndroidRuntime]    at mono.java.lang.RunnableImplementor.run(RunnableImplementor.java:30)
[AndroidRuntime]    at android.os.Handler.handleCallback(Handler.java:746)
[AndroidRuntime]    at android.os.Handler.dispatchMessage(Handler.java:95)
[AndroidRuntime]    at android.os.Looper.loop(Looper.java:148)
[AndroidRuntime]    at android.app.ActivityThread.main(ActivityThread.java:5443)
[AndroidRuntime]    ... 3 more

I've this code in a PCL. Why am I getting this error? How do I get the cookies correctly?

EDIT:

Now I've modernhttpclient library in both my pcl and ios project to make it work. If I remove it from the ios project. I get the same error.

Answer 1

For future googlers: it may happen when you update some NuGet reference (e.g. modernhttpclient-updated) to a version which targets Xamarin.Android 8.1 (just for example) while your app targets Xamarin.Android 6.0: in that case your Xamarin.Android project wouldn't reference platform-specific code but only shared.

Pay attention to NuGet warning!