Projac Generic ConnectedProjection

ConnectedProjection.cs

/// <summary>
///     Represent a connected projection.
/// </summary>
public abstract class ConnectedProjection<TConnection>
{
    private readonly List<ConnectedProjectionHandler<TConnection>> _handlers;

    /// <summary>
    ///     Initializes a new instance of the <see cref="ConnectedProjection{TConnection}" /> class.
    /// </summary>
    protected ConnectedProjection()
    {
        _handlers = new List<ConnectedProjectionHandler<TConnection>>();
    }

    /// <summary>
    ///     Specifies the message handler to be invoked when a particular message occurs.
    /// </summary>
    /// <typeparam name="TMessage">The type of the message.</typeparam>
    /// <param name="handler">The message handler.</param>
    /// <exception cref="System.ArgumentNullException">Thrown when <paramref name="handler" /> is <c>null</c>.</exception>
    protected void When<TMessage>(Func<TConnection, TMessage, Task> handler)
    {
        if (handler == null) throw new ArgumentNullException("handler");
        _handlers.Add(
            new ConnectedProjectionHandler<TConnection>(
                typeof (TMessage),
                (connection, message, token) => handler(connection, (TMessage) message)));
    }

    /// <summary>
    ///     Specifies the message handler to be invoked when a particular message occurs.
    /// </summary>
    /// <typeparam name="TMessage">The type of the message.</typeparam>
    /// <param name="handler">The message handler.</param>
    /// <exception cref="System.ArgumentNullException">Thrown when <paramref name="handler" /> is <c>null</c>.</exception>
    protected void When<TMessage>(Func<TConnection, TMessage, CancellationToken, Task> handler)
    {
        if (handler == null) throw new ArgumentNullException("handler");
        _handlers.Add(
            new ConnectedProjectionHandler<TConnection>(
                typeof (TMessage),
                (connection, message, token) => handler(connection, (TMessage) message, token)));
    }

    /// <summary>
    ///     Gets a read only collection of projection handlers.
    /// </summary>
    /// <value>
    ///     The projection handlers associated with this specification.
    /// </value>
    public ConnectedProjectionHandler<TConnection>[] Handlers
    {
        get { return _handlers.ToArray(); }
    }
}

ConnectedProjectionHandler.cs

/// <summary>
///     Represents a handler of a particular type of message.
/// </summary>
public class ConnectedProjectionHandler<TConnection>
{
    private readonly Type _message;
    private readonly Func<TConnection, object, CancellationToken, Task> _handler;

    /// <summary>
    ///     Initializes a new instance of the <see cref="ConnectedProjectionHandler{TConnection}" /> class.
    /// </summary>
    /// <param name="message">The message.</param>
    /// <param name="handler">The handler.</param>
    /// <exception cref="System.ArgumentNullException">
    ///     Throw when <paramref name="message" /> or <paramref name="handler" /> is
    ///     <c>null</c>.
    /// </exception>
    public ConnectedProjectionHandler(Type message, Func<TConnection, object, CancellationToken, Task> handler)
    {
        if (message == null) throw new ArgumentNullException("message");
        if (handler == null) throw new ArgumentNullException("handler");
        _message = message;
        _handler = handler;
    }

    /// <summary>
    ///     The type of message to handle.
    /// </summary>
    public Type Message
    {
        get { return _message; }
    }

    /// <summary>
    ///     The function that handles the message.
    /// </summary>
    public Func<TConnection, object, CancellationToken, Task> Handler
    {
        get { return _handler; }
    }
}