CODEWITHSUNDEEP
c#
crazydev
crazydev

Reputation: 575

How to detect a variable change and get the value of the variable in c#

I have made use of property changed event to assign a value to a bool value in an attempt to get the connectivity status.

However, I want to listen for this change of the variable from another class and perform some action. How can I achieve this in C# ?

private bool isDisconnected;

public bool IsDisconnected
{
    get { return isDisconnected; }
    set
    {
        isDisconnected = value;
        OnPropertyChanged("IsDisconnected");
    }

}

public event PropertyChangedEventHandler PropertyChanged;

public override void OnConnectionStateChange(BluetoothGatt gatt, [GeneratedEnum] GattStatus status, [GeneratedEnum] ProfileState newState)
{
    base.OnConnectionStateChange(gatt, status, newState);

    if(newState == ProfileState.Connected)
    {
        isDisconnected = true;
        gatt.DiscoverServices();
    }

    else if(newState == ProfileState.Disconnected)
    {
        gatt.Close();
        isDisconnected = true;
        Log.Info("BLE", "Status: Disconnected");
    }

}

In another class which is basically a Service, I want to listen for the variable IsDisconnected. Please someone help me.

My Service class: 

[return: GeneratedEnum]
public override StartCommandResult OnStartCommand(Intent intent, [GeneratedEnum] StartCommandFlags flags, int startId)
{
    try
    {
        Toast.MakeText(this, "Background service started", ToastLength.Long);
        t = new Thread(() =>
        {
            Task.Run(async () =>
            {
                ConnectionListener gatt = new ConnectionListener ();
                gatt.PropertyChanged += (s, e) =>
                {
                    if (e.PropertyName == nameof(GattCallback.IsDisconnected))
                    {

                    }
                };

            });
        });

        t.Start();
    }
}

Upvotes: 0

Views: 1499

Answers (1)

Martin Zikmund
Martin Zikmund

Reputation: 39072

Suppose the instance of your class is called connection. Then from another class you hook up the PropertyChanged event:

connection.PropertyChanged += (s,e) =>
{
   if (e.PropertyName == nameof(YourClass.IsDisconnected))
   { 
       //isDisconnected changed, perform your logic
   }
}

Of course this is just a sample code and it would be appropriate to move the event handling to a method if the two instances have different lifetime. By doing that you can later unsubscribe from the event so that you don't introduce memory leaks.

Also you need to update the GattCallback class to set the IsDisconnected property instead of the isDisconnected field in the OnConnectionChange method:

if(newState == ProfileState.Connected)
{
    IsDisconnected = false; //notice change true -> false
    gatt.DiscoverServices();
}

else if(newState == ProfileState.Disconnected)
{
    gatt.Close();
    IsDisconnected = true;
    Log.Info("BLE", "Status: Disconnected");
}

Also it seems you had a bug there - you were setting IsDisconnected to true in both cases, which is probably not what you want.

Upvotes: 3

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