Enterprise Library

Enterprise Library News

Alois Kraus — Tue, 04 Jul 2006 09:35:00 GMT

The world is turning and evolution of software is going on and on. It is time for another Enterprise Library Update. In the last few weeks an enormous amount of code has been produced by the Patterns & Practices Team. In case you did not download the Microsoft Enterprise Library for .NET 2.0 you should have a look into if you develop with ASP.NET serious web apps or
Enterprise Grade applications .
Here are the most important links regarding the deliverables of the Patterns and Practices Team of Microsoft:

Enterprise Library for .NET 2.0 Download and Patches (passport logon needed)
Smart Client Software Factory which uses Entlib, CAB GAT and GAX (Download).
Visual Studio Extensions to insert code templates via GAT (Guidance Automation Toolkit) and GAX (Download)
In case you have uninstall problems with the GAT/GAX you should consider downloading the MSI Installer Cleanup Utility (Download)

The stuff contained in these packages is a fine piece of well tested application blocks that represent the best industry practices for building Enterprise Grade applications with .NET 2.0.
Up to date information can be found at Tom Hollanders blog who will be glad (tell him that ;-)) to answer your questions. The most interesting posts are

Patch for Enterprise Library to work under partial trust (e.g. ASP.NET web apps will profit from this one).
July Community Drop of Web Service Software Factory where he does explain what this is all about.
What are GAT and GAX anyway?
Enterprise Library for .NET Framework 3.0 - what would you like to see?

Especially the last post of Tom has received a huge number of comments what we (the users of Entlib) would like to see in a future released targeting the .NET Framework 3.0. If you have ideas how you could improve the Enterprise Library or what additional application blocks you would like to see drop him a note. If you have problems installing GAT or GAX you should stop by at the Visual Studio Automation Toolkit forum to get help. My personal install experience with GAT/GAX was not pleasant at my home PC so far. I hope that I can get around this error without reinstalling VS 2005.

If you are a practicioning software architect you should definetely check out these new tools in your arsenal to create robust and extensible applications. The learning curve is high but we live in a complex world where many requirements want to be fullfilled. Java Script, AJAX and a SQL database is not the answer (at least in general) to all needs of Enterprise Grade software.

Enterprise Library Hands On Labs available

Alois Kraus — Mon, 08 May 2006 08:38:00 GMT

If you are not sure if the Enterprise Library for .NET 2.0 is the right thing for your application you should check out the new Hands on Labs. All six Application Blocks (Caching, Security, Cryptography, Data Access, Logging and Exceptions Handling) are shown in action with a detailed step for step introduction to get started with each of them. Another source of information mainly configuration of the Enterprise Library can be found in the articles of my blog.

Store your App.Config inside SQL Server

Alois Kraus — Tue, 18 Apr 2006 07:26:00 GMT

I did submit some time ago a little fix for the Enterprise Library SqlConfigurationSource but I did not yet have time to blog about it. Better late than never I want to shed some light (again) on configuration. To get your application settings from your local disk you can use the .NET ConfigurationManager class or the (Entlib) FileConfigurationSource to fetch the settings from another file than your App.Config file.
The Enterprise Library SqlConfigurationManager is the counterpart to the .NET ConfigurationManager class and can be directly used from any application that cares about central configuration. To use it you need a running SQL Server 2005 (Express) server and a database which contains some stored procedures which are responsible for reading and writing ConfigurationSections. The following code sample shows you how to get your settings with only a few lines of code from SQL server.

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Extend the Enterprise Library Config Tool - A Configurable Assembly Loader

Alois Kraus — Mon, 06 Mar 2006 10:45:00 GMT

It has been some time since my last post. But I have an excuse: I did work on an improved version of the graphical EntlibConfig tool. The code can
be downloaded from the Sample Section of Gotdotnet. When you install the Jan 2006 of EntLib all works fine as long as EntLib is the only project in your bin folder. But for real Enterprise scenarios this is not true. The bin folder of your project is crowded soon with all sorts of other dlls and executables. Some might be managed some not, others might even require special permissions (Interop.WindowsInstaller.dll which will throw during assembly load an SecurityException). These problems can cause a significant startup delay or break the tool completely. The config tool itself is decoupled all application blocks and loads them via the Dependency Injection Pattern another good source of information about this pattern can be found at the web site of the Spring.NET framework. This loose coupling is nice from the architectural point of view but can get in your way when you want to start the tool. Since there are no references to other projects tool does load the rest of the GUI via the following mechanism:

Load all assemblies in deployment directory of EntlibConfig.exe.
Check each assembly for the ConfigurationDesignManagerAttribute and plug it into the UI hierarchy.

This approach does introduce some problems:

Increased startup time.
Loading unmanaged Dlls or some Interop assemblies which break the tool completely.
Unable to load App.config which references other EntLib extensions which are not located in the folder where the tool resides.

I have tried to circumvent these issues by making it configurable what (Design) assemblies are loaded at startup and where to look for missing references. If you load e.g. the Logging QuickStart sample App.config into the tool it will show you the following error:

With my extension you will see instead the Assembly Loader configuration dialog which does let you add the missing dependency at run time without the need to restart the tool.

To add the missing dependency you have two options:

a) Add the assembly in question to the ones which are loaded during startup.
b) Add an assembly resolve folder where to look also when resolving missing dependencies.

I would recommend to use option b) for assemblies which do not contain any design time (*.Design.dll) parts for the UI itself. This way you can load all UI extenstion at startup from any folder you would want. To enable XCopy deployment I made all selected paths/files relative to the Appdomain directory of the EntLib tool. After clicking OK the new settings are saved in your User profile (NOT EntlibConfig.exe.config) and the assembly bind is tried again. You should now see the UI without any further investigation what dependency might be missing. To make things complete you can fire up this dialog via the File Menu of the EntlibConfig tool

The integration of the Enterprise Library and its config tool into a real Source Control System (no not Visual Source Safe) is much easier now. I have delivered a default configuration in the Enterprise Library App.Config file which explains the blue items in the dialogs. You can still change the assembly resolve directories and loaded assemblies at startup since the configuration is stored in the current users profile. With this twofold approach you can deliver presets which cannot be changed and give at the same time the user (developer) the freedom to add the needed dependencies on the fly without the need to check out the EntlibConfig.exe.config file from the source control system.

Lessons learned

During the development of this Addon I have found that it makes perfect sense to use Visual Source Safe on a Single User Machine. I had to review my changes compared to the "official" Enterprise Library which is with a Source Control system much easier. As always during development unexpected things happen which make you wonder why your application behaves so strange.

Problems/Bugs found:

When you add a settings collection with an auto generated settings class I receive in the Appdomain.CurrentDomain.AssemblyResolve event handler the request for a not existing "System.XmlSerializers" assembly. This might have sth. to do with the on the fly generated assemblies by XmlSerializer but I do not understand why I should know about this. In the handler I had to alter my application logic to skip this not existing assembly. If you consider this a bug you can vote here.
After showing the Open File Dialog the current working directory is changed which did cause my relative path expansion algorithm blow up. There is a settings OpenFileDialog.RestoreDirectory which you can set to true to get the desired behavior. I found it out after filing a request at the Product Feedback Center. It would be nice to document this in the Path.GetFullPath function documentation. It is not easy to understand why the application behaves differently after the File Open Dialog.

I hope this gives you better understanding what problems you are faced with when you deploy a software package which contains third party software or what constraints you have when you want to enable software to run as checked in version in a source control system.

Programatic Configuraton - Enterprise Library (v2.0) Logging Block

Alois Kraus — Fri, 17 Feb 2006 09:39:00 GMT

The following code sample shows how to configure the Enterprise Library Logging Block programatically without the help of ObjectBuilder. To create a working LogWriter instance with your own settings you need to create the following objects:
A Formatter which contains a valid message template
A LogSource which has a name (Category) contains a colleciton of Listeners (Sinks) along with the Formatter.
A collection LogSources with the category as key and the LogSource object as value
To use this logger you can call

ConfigLessLogger.Error("Hello world of config by code."); 
The error is written to the Windows Event Application Event Log:

Timestamp: 16.02.2006 23:33:41
Message: Hello World of dynamic object creation
Category: Errors

I have improved my original ConfigLessLogger sample with the very helpful comments from David Hayden who blogs about the Enterprise Library (mainly IConfigurationSource and Logging Block).
ConfigLessLoger.cs

using System;
using System.Collections.Generic;
using Microsoft.Practices.EnterpriseLibrary.Logging;
using Microsoft.Practices.EnterpriseLibrary.Common.Configuration;
using Microsoft.Practices.EnterpriseLibrary.Logging.Filters;
using Microsoft.Practices.EnterpriseLibrary.Logging.Formatters;
using Microsoft.Practices.EnterpriseLibrary.Logging.TraceListeners;
 
namespace MyApp.Logging
{
    public class ConfigLessLogger
    {
        private static LogWriter writer;              // Instance is created in static ctor which is thread safe
        const string EventLogSource = "Code Source";  // Event Log Source name
        const string ErrorCategory = "Errors";        // We have only one message category: Errors 
 
        static ConfigLessLogger()
        {
            writer = CreateLogWriterFromCode();  // static ctor is thread safe according to ECMA standard section 9.5.3 
        }
 
        static private LogWriter CreateLogWriterFromCode()
        {
            // This is our message template for any Sink you add below in our case the Windows Event Log
            TextFormatter formatter = new TextFormatter("Timestamp: {timestamp}{newline}" +
                                                        "Message: {message}{newline}"    +
                                                        "Category: {category}{newline}"    );
 
            LogSource emptyTraceSource = new LogSource("none");
 
            LogSource errorsTraceSource = new LogSource(ErrorCategory, System.Diagnostics.SourceLevels.All);
            // Create for all Errors a Listener which writes the messages to the Windows Event Log
            // with the Event Log Source Property "Code Source". The message format is specified by
            // the TextFormatter which is in our case the template above.
            errorsTraceSource.Listeners.Add(new FormattedEventLogTraceListener(EventLogSource, formatter));
 
            IDictionary<string, LogSource> traceSources = new Dictionary<string, LogSource>();
            // Add to Category "Error" our EventLog Listener with the corresponding category in it.
            traceSources.Add(errorsTraceSource.Name, errorsTraceSource);
 
            return new LogWriter(new ILogFilter[0], // ICollection<ILogFilter> filters
                              traceSources,        // IDictionary<string, LogSource> traceSources
                              emptyTraceSource,    // LogSource allEventsTraceSource
                              emptyTraceSource,    // LogSource notProcessedTraceSource
                              errorsTraceSource,    // LogSource errorsTraceSource
                              ErrorCategory,        // string defaultCategory
                              false,                // bool tracingEnabled
                              true);                // bool logWarningsWhenNoCategoriesMatch
        }
 
        /// <summary>
        /// Write an Error message to the Windows Event Log with an message template specifed in code
        /// </summary>
        /// <param name="message">Error message to log</param>
        public static void Error(string message)
        {
            LogEntry ent = new LogEntry();
            ent.Categories.Add(ErrorCategory);  // To use another category use traceSources.Add("OtherCat", Listener);
            ent.Message = message;
            ent.Severity = System.Diagnostics.TraceEventType.Error;
            writer.Write(ent);
        }
    }
}