/V4/PrismLibrary/Desktop/Prism/Modularity/AssemblyResolver.Desktop.cs

//===================================================================================

// Microsoft patterns & practices

// Composite Application Guidance for Windows Presentation Foundation and Silverlight

//===================================================================================

// Copyright (c) Microsoft Corporation.  All rights reserved.

// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY

// OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT

// LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND

// FITNESS FOR A PARTICULAR PURPOSE.

//===================================================================================

// The example companies, organizations, products, domain names,

// e-mail addresses, logos, people, places, and events depicted

// herein are fictitious.  No association with any real company,

// organization, product, domain name, email address, logo, person,

// places, or events is intended or should be inferred.

//===================================================================================

using System;

using System.Collections.Generic;

using System.IO;

using System.Linq;

using System.Reflection;

using Microsoft.Practices.Prism.Properties;



namespace Microsoft.Practices.Prism.Modularity

{

    /// <summary>

    /// Handles AppDomain's AssemblyResolve event to be able to load assemblies dynamically in 

    /// the LoadFrom context, but be able to reference the type from assemblies loaded in the Load context.

    /// </summary>

    public class AssemblyResolver : IAssemblyResolver, IDisposable

    {

        private readonly List<AssemblyInfo> registeredAssemblies = new List<AssemblyInfo>();



        private bool handlesAssemblyResolve;



        /// <summary>

        /// Registers the specified assembly and resolves the types in it when the AppDomain requests for it.

        /// </summary>

        /// <param name="assemblyFilePath">The path to the assemly to load in the LoadFrom context.</param>

        /// <remarks>This method does not load the assembly immediately, but lazily until someone requests a <see cref="Type"/>

        /// declared in the assembly.</remarks>

        public void LoadAssemblyFrom(string assemblyFilePath)

        {

            if (!this.handlesAssemblyResolve)

            {

                AppDomain.CurrentDomain.AssemblyResolve += this.CurrentDomain_AssemblyResolve;

                this.handlesAssemblyResolve = true;

            }



            Uri assemblyUri = GetFileUri(assemblyFilePath);



            if (assemblyUri == null)

            {

                throw new ArgumentException(Resources.InvalidArgumentAssemblyUri, "assemblyFilePath");

            }



            if (!File.Exists(assemblyUri.LocalPath))

            {

                throw new FileNotFoundException();

            }



            AssemblyName assemblyName = AssemblyName.GetAssemblyName(assemblyUri.LocalPath);

            AssemblyInfo assemblyInfo = this.registeredAssemblies.FirstOrDefault(a => assemblyName == a.AssemblyName);



            if (assemblyInfo != null)

            {

                return;

            }



            assemblyInfo = new AssemblyInfo() { AssemblyName = assemblyName, AssemblyUri = assemblyUri };

            this.registeredAssemblies.Add(assemblyInfo);

        }



        private static Uri GetFileUri(string filePath)

        {

            if (String.IsNullOrEmpty(filePath))

            {

                return null;

            }



            Uri uri;

            if (!Uri.TryCreate(filePath, UriKind.Absolute, out uri))

            {

                return null;

            }



            if (!uri.IsFile)

            {

                return null;

            }



            return uri;

        }



        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Reliability", "CA2001:AvoidCallingProblematicMethods", MessageId = "System.Reflection.Assembly.LoadFrom")]

        private Assembly CurrentDomain_AssemblyResolve(object sender, ResolveEventArgs args)

        {

            AssemblyName assemblyName = new AssemblyName(args.Name);



            AssemblyInfo assemblyInfo = this.registeredAssemblies.FirstOrDefault(a => AssemblyName.ReferenceMatchesDefinition(assemblyName, a.AssemblyName));



            if (assemblyInfo != null)

            {

                if (assemblyInfo.Assembly == null)

                {

                    assemblyInfo.Assembly = Assembly.LoadFrom(assemblyInfo.AssemblyUri.LocalPath);

                }



                return assemblyInfo.Assembly;

            }



            return null;

        }



        private class AssemblyInfo

        {

            public AssemblyName AssemblyName { get; set; }



            public Uri AssemblyUri { get; set; }



            public Assembly Assembly { get; set; }

        }



        #region Implementation of IDisposable



        /// <summary>

        /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.

        /// </summary>

        /// <remarks>Calls <see cref="Dispose(bool)"/></remarks>.

        /// <filterpriority>2</filterpriority>

        public void Dispose()

        {

            this.Dispose(true);

            GC.SuppressFinalize(this);

        }



        /// <summary>

        /// Disposes the associated <see cref="AssemblyResolver"/>.

        /// </summary>

        /// <param name="disposing">When <see langword="true"/>, it is being called from the Dispose method.</param>

        protected virtual void Dispose(bool disposing)

        {

            if (this.handlesAssemblyResolve)

            {

                AppDomain.CurrentDomain.AssemblyResolve -= this.CurrentDomain_AssemblyResolve;

                this.handlesAssemblyResolve = false;

            }

        }



        #endregion

    }

}