CODEWITHSUNDEEP
c#interface
David
David

Reputation: 39

c# interface implementation error

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)

Upvotes: 1

Views: 1296

Answers (3)

Gilad Green
Gilad Green

Reputation: 37281

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.

Upvotes: 5

nvoigt
nvoigt

Reputation: 77364

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.

Upvotes: 2

Aleksandar Matic
Aleksandar Matic

Reputation: 799

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)

Upvotes: 1

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