How to connect to local network first instead of internet in C# Xamarin Android app?

Question

I have a Xamarin Android app. It connects to a “No Internet based Wifi router” for some IOT devices. But it also needs to use mobile’s cellular data for storing some informa

Answer 1

After lot of tries and failures, I was able to implement the approach provided here: Stackoverflow Link

I changed this code from Java to Xamarin C# and was able to force Cellular or Wifi as the preferred network programmatically.

My implementation:

using Android.Net;
public SomeClass{
    public static Context _context = Android.App.Application.Context;

    ....

    /// 

    /// Forces the wifi over cellular.
    /// 
    public static void ForceWifiOverCellular()
    {
        ConnectivityManager connection_manager = (ConnectivityManager)_context.GetSystemService(Context.ConnectivityService);

        NetworkRequest.Builder request = new NetworkRequest.Builder();
        request.AddTransportType(TransportType.Wifi);

        var callback = new ConnectivityManager.NetworkCallback();
        connection_manager.RegisterNetworkCallback(request.Build(), new CustomNetworkAvailableCallBack());

    }

    /// 

    /// Forces the cellular over wifi.
    /// 
    public static void ForceCellularOverWifi()
    {
        ConnectivityManager connection_manager = (ConnectivityManager)_context.GetSystemService(Context.ConnectivityService);

        NetworkRequest.Builder request = new NetworkRequest.Builder();
        request.AddTransportType(TransportType.Cellular);

        connection_manager.RegisterNetworkCallback(request.Build(), new CustomNetworkAvailableCallBack());
    }
}


/// 

/// Custom network available call back.
/// 
public class CustomNetworkAvailableCallBack : ConnectivityManager.NetworkCallback
{
    public static Context _context = Android.App.Application.Context;

    ConnectivityManager connection_manager = (ConnectivityManager)_context.GetSystemService(Context.ConnectivityService);

    public override void OnAvailable(Network network)
    {
        //ConnectivityManager.SetProcessDefaultNetwork(network);    //deprecated (but works even in Android P)
        connection_manager.BindProcessToNetwork(network);           //this works in Android P
    }
}

Usage:

1. Where I need to force Cellular, just call:

SomeClass.ForceCellularOverWifi();

2. Where I need to force Wifi, just call:

SomeClass.ForceWifiOverCellular();

Hope this helps others.