c# interface implementation error

Question

I'm developing a communication manager for my app, that is designed like this:

ICommunicator interface, a general communicator.

public interface ICommunicator
{
    bool openConnection();
    bool closeConnection();

    bool isConnectionOpen();
    Form getConfigurationForm();

    void Data_Input(object sender, EventArgs e);
}

and currently, a single concrete communicator which is SerialCommunicator:

public class SerialCommunicator : ICommunicator
{
    public delegate bool setPortDelegate(string portName);
    public delegate bool setBaudRateDelegate(int baudRate);

    private SerialPort serial;

    public SerialCommunicator()
    {
        serial = new SerialPort();
        loadDefaultSerialPreset(serial);
        serial.DataReceived += Data_Input;
    }

    public bool openConnection()
    {
        if (serial.IsOpen)
        {
            return false;
        }
        try
        {
            serial.Open();
        }
        catch (Exception)
        {
            //could not open the port
            return false;
        }

        return serial.IsOpen;
    }

    public bool closeConnection()
    {
        try
        {
            serial.Close();
        }
        catch (Exception)
        {
            return false;
        }
        return !serial.IsOpen;
    }

    public bool isConnectionOpen()
    {
        return this.serial.IsOpen;
    }

    public bool sendData(String text)
    {
        if (!this.serial.IsOpen)
        { return false; }

        return true;
    }

    public void Data_Input(object sender, SerialDataReceivedEventArgs e)
    {
        String s = serial.ReadLine();
        //tbd
    }

    public Form getConfigurationForm()
    {
        return new portConf(setPortName, setBaudRate);
    }

    private bool setPortName(string portName)
    {
        if (portName == null || portName.Length < 1 || !portName.StartsWith("COM"))
        {
            return false;
        }
        if (serial.IsOpen)
        {
            return false;
        }
        serial.PortName = portName;
        return true;
    }

    private bool setBaudRate(int baudRate)
    {
        if (baudRate < 9600 || baudRate > 115200)
        {
            return false;
        }
        if (serial.IsOpen)
        {
            return false;
        }
        serial.BaudRate = baudRate;
        return true;
    }

    private void loadDefaultSerialPreset(SerialPort s)
    {
        //default preset
        s.BaudRate = 115200;
        s.PortName = "COM1";
        //default settings
        s.DataBits = 8;
        s.DiscardNull = false;
        s.DtrEnable = false;
        s.Handshake = Handshake.None;
        s.Parity = Parity.None;
        s.ParityReplace = 63;
        s.ReadBufferSize = 4096;
        s.ReadTimeout = -1;
        s.ReceivedBytesThreshold = 1;
        s.RtsEnable = false;
        s.StopBits = StopBits.One;
        s.WriteBufferSize = 2048;
        s.WriteTimeout = -1;
    }
}

the problem is, the compiler says that SerialCommunicator does not implement the interface:

'SerialCommunicator' does not implement interface member 'ICommunicator.Data_Input(object, EventArgs)'

I can not understand why it gives me that error. I do have the Data_Input(object, SerialDataReceivedEventArgs) , although every SerialDataReceivedEventArgs is also an EventArgs object.

Why does the compiler gives me that problem, and how can I fix it (I do need that event for other types of communication)

Answer 1

These too:

//Interface
void Data_Input(object sender, EventArgs e);
// Derived class
public void Data_Input(object sender, SerialDataReceivedEventArgs e)

Are not the same thing - They are 2 different types. When implementing an interface the signatures must be identical to those in the interface.

You should change the derived to be exactly like the interface or use a generic parameter + constraint.

//Interface
public interface ICommunicator<TEventArgs>
    where TEventArgs : EventArgs
{
    void Data_Input(object sender, TEventArgs e);
}

//Derived
public class SerialCommunicator : ICommunicator<SerialDataReceivedEventArgs>
{
    public void Data_Input(object sender, SerialDataReceivedEventArgs e)
    {
        throw new NotImplementedException();
    }
}

Even if you do not use the generics here, keep in mind that though the method will have a EventArgs parameter to it you can of course pass a derived type to it.

Answer 2

I can not understand why it gives me that error. I do have the Data_Input(object, SerialDataReceivedEventArgs) , although every SerialDataReceivedEventArgs is also an EventArgs object.

Although SerialDataReceivedEventArgs is an EventArgs , your interface declares a method that can be passed an EventArgs and the method you implemented does not accept an EventArgs , but only the more specialized SerialDataReceivedEventArgs . So your implementation does not fulfill the contract that is required.

Answer 3

Interface:

void Data_Input(object sender, EventArgs e);

Your implementation:

public void Data_Input(object sender, SerialDataReceivedEventArgs e)

You need to have this:

public void Data_Input(object sender, EventArgs e)