Helper class to load resources strings.

//===============================================================================
// Microsoft patterns & practices Enterprise Library
// Core
//===============================================================================
// Copyright © 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.
//===============================================================================

using System;
using System.Reflection;
using System.Resources;

namespace Microsoft.Practices.EnterpriseLibrary.Common
{
    /// <summary>
    /// Helper class to load resources strings.
    /// </summary>
    public static class ResourceStringLoader
    {
        /// <summary>
        /// Load a resource string.
        /// </summary>
        /// <param name="baseName">The base name of the resource.</param>
        /// <param name="resourceName">The resource name.</param>
        /// <returns>The string from the resource.</returns>
        public static string LoadString(string baseName, string resourceName)
        {
            return LoadString(baseName, resourceName, Assembly.GetCallingAssembly());
        }

        /// <summary>
        /// Load a resource string.
        /// </summary>
        /// <param name="baseName">The base name of the resource.</param>
        /// <param name="resourceName">The resource name.</param>
        /// <param name="asm">The assembly to load the resource from.</param>
        /// <returns>The string from the resource.</returns>
        public static string LoadString(string baseName, string resourceName, Assembly asm)
        {
            if (string.IsNullOrEmpty(baseName))
            {
                throw new ArgumentNullException("baseName");
            }
            if (string.IsNullOrEmpty(resourceName))
            {
                throw new ArgumentNullException("resourceName");
            }

            string value = null;

            if (null != asm)
            {
                value = LoadAssemblyString(asm, baseName, resourceName);
            }
            if (null == value && null != asm)
            {
                value = SearchForResource(asm, resourceName);
            }
            if (null == value)
            {
                value = LoadAssemblyString(Assembly.GetExecutingAssembly(), baseName, resourceName);
            }
            if (null == value)
            {
                return string.Empty;
            }

            return value;
        }

        private static string SearchForResource(Assembly asm, string resourceName)
        {
            string[] resources = asm.GetManifestResourceNames();

            foreach (string resource in resources)
            {
                // Remove additional .resource token
                const string token = ".resources";
                string resourceToUse = resource;
                if (resource.EndsWith(token, StringComparison.OrdinalIgnoreCase))
                {
                    resourceToUse = resource.Replace(token, string.Empty);
                }

                string result = LoadAssemblyString(asm, resourceToUse, resourceName);

                if (!string.IsNullOrEmpty(result))
                {
                    return result;
                }
            }

            return null;
        }

        private static string LoadAssemblyString(Assembly asm, string baseName, string resourceName)
        {
            try
            {
                ResourceManager rm = new ResourceManager(baseName, asm);
                return rm.GetString(resourceName);
            }
            catch (MissingManifestResourceException)
            {
            }

            return null;
        }
    }
}