EventArgs data usage

Question

I have three classes, the FileManagerClass contains two events which are EventHandler<FileTransferEventArgs> FileMove and EventHandler<FileTransferEventArgs> FileMoveError.

I then have a custom EventArgs class named FileTransferEventArg that inherits from the base EventArgs class. I have a third class called FolderDirectoryModel that then listens for the events to be raised and responds to it with either a OnFileMove(object sender, FileTransferEventArg arg) or OnFileMoveError(object sender, FileTransferEventArg arg).

Overall, it looks like this:

class FileTransferManager
{
    public event EventHandler<FileTransferEventArgs> FileMove;
    public event EventHandler<FileTransferEventArgs> FileMoveError;
}

public class FileTransferEventArgs : EventArgs
{
    string FileName { get; set; }
    string Message { get; set; }

    internal FileTransferEventArgs(FileModel file, string message)
    {
        this.FileName = file.FileName;
        this.Message = message;
    }
}

public class FolderDirectoryModel
{
    void TransferFile(FileModel toBeTransfered, string destinationPath)
    {
        if (!File.Exists(toBeTransfered.FilePath))
        {
            File.Move(toBeTransfered.FilePath, destinationPath);
            FileTransferEvents.FileTransferManager TransferAgent = new FileTransferEvents.FileTransferManager();
            TransferAgent.FileMove += new EventHandler<FileTransferEventArgs>(OnFileMove);                
        }
        else
        {
            FileTransferEvents.FileTransferManager TransferAgent = new FileTransferEvents.FileTransferManager();
            TransferAgent.FileMoveError += new EventHandler<FileTransferEventArgs>(OnFileMoveError);
        }
    }

    //Handler Methods
    private void OnFileMoveError(object sender, FileTransferEventArgs args)
    {
        //what i want to happen

        MessageBox.Show($"File {args.FileName} has not been moved succefully to {args.FilePath} because of....");
    }

    private void OnFileMove(object sender, FileTransferEventArgs args)
    {
        //what i want to happen
        MessageBox.Show($"File {args.FileName} has been moved successfully to {args.FilePath}
    }
}

My problem is that I would like to use the properties inside my FileTransferEventArgs class to display the file name that was moved, whether or not it was successful, and providing a reason that will be inside the message property.

However when I get every thing wired up I not able to view the data that is passed along. I am not sure if I am improperly using the events or I am trying to do something that is not possible.

Answer 1

The FileMove and FileMoveError events must be placed in the FolderDirectoryModel class.

Events are triggered in the same class. Using the Invoke method.

public class FileTransferEventArgs : EventArgs
{
    public string FileName { get; }
    public string FilePath { get; }
    public string Message { get; }

    internal FileTransferEventArgs(FileModel file, string message)
    {
        FileName = file.FileName;
        FilePath = file.FilePath;
        Message = message;
    }
}

public class FileModel
{
    public string FileName { get; set; }
    public string FilePath { get; set; }
}

public class FolderDirectoryModel
{
    public event EventHandler<FileTransferEventArgs> FileMove;
    public event EventHandler<FileTransferEventArgs> FileMoveError;

    public void TransferFile(FileModel fileModel, string destinationPath)
    {
        if (!File.Exists(fileModel.FilePath))
        {
            File.Move(fileModel.FilePath, destinationPath);
            var fileTransferEventArgs = new FileTransferEventArgs(fileModel, "Success");
            FileMove?.Invoke(this, fileTransferEventArgs);
        }
        else
        {
            var fileTransferEventArgs = new FileTransferEventArgs(fileModel, "Cannot move");
            FileMoveError?.Invoke(this, fileTransferEventArgs);
        }
    }
}

Usage

var fileModel = new FileModel { FileName = "name", FilePath = "path" };

var folderDirectoryModel = new FolderDirectoryModel();
folderDirectoryModel.FileMove += FolderDirectoryModel_FileMove;
folderDirectoryModel.FileMoveError += FolderDirectoryModel_FileMoveError;

folderDirectoryModel.TransferFile(fileModel, "destPath");

void FolderDirectoryModel_FileMove(object sender, FileTransferEventArgs args)
{
    MessageBox.Show($"File {args.FileName} has been moved successfully to {args.FilePath}");
}

void FolderDirectoryModel_FileMoveError(object sender, FileTransferEventArgs args)
{
    MessageBox.Show($"File {args.FileName} has not been moved to {args.FilePath} because of {args.Message}");
}

Event handlers are located in the same code where the FolderDirectoryModel instance is created and used.