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Model View Presenter via .NET

, 10 Oct 2009 CPOL 43.1K 1.5K 73
An article outlining an implementation of the Model View Presenter pattern in .NET, contrasting it with existing implementations of MVP, MVC, and using co-dependant interfaces to allow for abstract coordination.
ExampleProject.zip
ExampleProject.Contracts
bin
Debug
CobaltSoftware.Foundation.ModelViewPresenter.dll
ExampleProject.Contracts.dll
Properties
ExampleProject.Model
bin
Debug
CobaltSoftware.Foundation.ModelViewPresenter.dll
ExampleProject.Contracts.dll
ExampleProject.Model.dll
Properties
ExampleProject.Presenters
bin
Debug
CobaltSoftware.Foundation.ModelViewPresenter.dll
ExampleProject.Contracts.dll
ExampleProject.Presenters.dll
Properties
ExampleProject.Views
bin
Debug
CobaltSoftware.Foundation.ModelViewPresenter.dll
ExampleProject.Contracts.dll
ExampleProject.Views.dll
Properties
CobaltSoftware.Foundation.ModelViewPresenter
bin
Debug
CobaltSoftware.Foundation.ModelViewPresenter.dll
Core
Properties
Support
ExampleProject.Application
bin
Debug
CobaltSoftware.Foundation.ModelViewPresenter.dll
ExampleProject.Application.exe
ExampleProject.Application.vshost.exe
ExampleProject.Application.vshost.exe.manifest
ExampleProject.Contracts.dll
ExampleProject.Model.dll
ExampleProject.Presenters.dll
ExampleProject.Views.dll
Properties
Settings.settings
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Diagnostics;

namespace CobaltSoftware.Foundation.ModelViewPresenter
{
    /// <summary>
    ///     The PresenterBase class provides common functionality for managing the views
    ///     associated with a presenter type. This allows for quicker construction of 
    ///     basic views without the implementation of large volumes of boilerplate code.
    /// </summary>
    /// <remarks>
    ///     <para>
    ///         <list>
    ///             <listheader>Version History</listheader>
    ///             <item>10 October, 2009 - Steve Gray - Initial Draft</item>
    ///         </list>
    ///     </para>
    ///     <para>
    ///         This implementation uses self-constrained generics to allow
    ///         bi-directional strong coupling of interface types for both
    ///         presenter and view, allowing mutual strong references.
    ///     </para>
    /// </remarks>
    /// <typeparam name="TPresenterContract">Presenter contract type</typeparam>
    /// <typeparam name="TViewContract">View contract type</typeparam>
    public abstract class PresenterBase<TPresenterContract, TViewContract> :
        IPresenter<TPresenterContract, TViewContract>,
        IViewManager<TViewContract, TPresenterContract>
        where TViewContract : IView<TViewContract, TPresenterContract>
        where TPresenterContract : IPresenter<TPresenterContract, TViewContract>
    {
        #region Private Fields

        private IList<TViewContract> _Views;

        #endregion

        #region Constructor(s)

        /// <summary>
        ///     Initialize the new presenter base class.
        /// </summary>
        public PresenterBase()
        {
            // Set up the initial, empty views list
            _Views = new List<TViewContract>();
        }

        #endregion

        #region Methods

        /// <summary>
        ///     Refresh a view / push initial state values into the view.
        /// </summary>
        /// <param name="viewInstance">View instance to refresh</param>
        protected abstract void RefreshView(TViewContract viewInstance);

        /// <summary>
        ///     Get the presenter contract endpoint represented by this
        ///     presenter base.
        /// </summary>
        /// <returns>Presenter contract endpoint.</returns>
        protected abstract TPresenterContract GetPresenterEndpoint();

        #endregion

        #region IViewManager<TViewContract,TPresenterContract> Members

        /// <summary>
        ///     Event that fires prior to each view being registered.
        /// </summary>
        public event PresenterEvent<TViewContract, TPresenterContract> BeforeViewConnect;

        /// <summary>
        ///     Event that fires after the view has been registered.
        /// </summary>
        public event PresenterEvent<TViewContract, TPresenterContract> AfterViewConnect;

        /// <summary>
        ///     Event that fires prior to a view un-registering itself
        /// </summary>
        public event PresenterEvent<TViewContract, TPresenterContract> BeforeViewDisconnect;

        /// <summary>
        ///     Event that fires after a view has unregistered.
        /// </summary>
        public event PresenterEvent<TViewContract, TPresenterContract> AfterViewDisconnect;

        #endregion

        #region IPresenter<TPresenterContract,TViewContract> Members

        /// <summary>
        ///     Connect a view to this presenter.
        /// </summary>
        /// <param name="viewInstance">View instance</param>
        /// <param name="requiresState">Requires initial state to be pushed into view.</param>
        public void ConnectView(TViewContract viewInstance, bool requiresState)
        {
            // Test invariants
            Debug.Assert(Views != null, "The views collection should always be available.");

            // Validate arguments
            if (viewInstance == null)
                throw new ArgumentNullException("viewInstance");

            lock (Views)
            {
                // If already registered, do nothing
                if (Views.Contains(viewInstance))
                    return;

                // Before the view connects, fire the appropriate events.
                if (BeforeViewConnect != null)
                    BeforeViewConnect(GetPresenterEndpoint(), viewInstance);

                // Add to views collection
                this._Views.Add(viewInstance);

                // Set initial state/refresh
                if (requiresState)
                    RefreshView(viewInstance);

                // After the view connects, fire the appropriate events.
                if (AfterViewConnect != null)
                    AfterViewConnect(GetPresenterEndpoint(), viewInstance);
            }
        }

        /// <summary>
        ///     Disconnect a view from this presenter.
        /// </summary>
        /// <param name="viewInstance">View instance</param>
        public void DisconnectView(TViewContract viewInstance)
        {
            // Test invariants
            Debug.Assert(Views != null, "The views collection should always be available.");

            // Validate arguments
            if (viewInstance == null)
                throw new ArgumentNullException("viewInstance");

            lock (Views)
            {
                // If not registered, do nothing
                if (!Views.Contains(viewInstance))
                    return;

                // Before the view disconnects, fire the appropriate events.
                if (BeforeViewDisconnect != null)
                    BeforeViewDisconnect(GetPresenterEndpoint(), viewInstance);

                // Remove from views collection
                this._Views.Remove(viewInstance);

                // After the view disconnects, fire the appropriate events.
                if (AfterViewDisconnect != null)
                    AfterViewDisconnect(GetPresenterEndpoint(), viewInstance);
            }
        }

        #endregion

        #region Properties

        /// <summary>
        ///     Views that are currently connected to this presenter.
        /// </summary>
        protected IEnumerable<TViewContract> Views
        {
            get
            {
                return _Views;
            }
        }

        #endregion
    }
}

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This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Steven James Gray
Software Developer (Senior) Insurance Industry
United Kingdom United Kingdom
Steve Gray is a Senior Developer at a British insurance company, working on a popular aggregator. When he's not writing ASP .NET, it's because there's SQL or WCF to write instead.

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