One of the ideas behind the PostSharp Toolkits was a zero code change requirement, that would allow you to simply install the relevant toolkit from NuGet, rebuild your project and that’s it. To achieve that, we have revived the PostSharp XML configuration. The XML configuration is the unification of the Plug-in and Project models in the project loader. Let’s have a look on how PostSharp Diagnostics Toolkits use this XML configuration.
PSPROJ XML Configuration
After installing the PostSharp Diagnostics Toolkits via NuGet, a file with the .psproj extension will be created, named after the current project. The .psproj files are an XML representation of the PostSharp Project structure – containing the configuration of the application, with resolved properties and references.
Let’s take a look at the default configuration that is produced by the PostSharp Diagnostic Toolkit package:
<?xml version="1.0" encoding="utf-8" ?>
<!-- Default project used when PostSharp is detected according to project references. -->
<Project xmlns="http://schemas.postsharp.org/1.0/configuration"
ReferenceDirectory="{$ReferenceDirectory}">
<Property Name="LoggingBackend" Value="trace" />
<Using File="default"/>
<Using File="..\..\Build\bin\{$Configuration}\PostSharp.Toolkit.Diagnostics.Weaver.dll"/>
<Tasks>
<XmlMulticast />
</Tasks>
<Data Name="XmlMulticast">
<LogAttribute
xmlns="clr-namespace:PostSharp.Toolkit.Diagnostics;assembly:PostSharp.Toolkit.Diagnostics" />
<LogAttribute
xmlns="clr-namespace:PostSharp.Toolkit.Diagnostics;assembly:PostSharp.Toolkit.Diagnostics"
AttributeExclude="true"
AttributeTargetMembers="regex:get_.*|set_.*" />
</Data>
</Project>
Let’s look at the properties more closely:
Project – the XML root node – defines the PostSharp Project configuration.
The property LoggingBackend specifies the logger that should be used by the Diagnostics Toolkit. This value is set during the installation of the toolkit via NuGet. The supported values in the PostSharp Diagnostics Toolkit package are trace (default) and console. Additional packages, PostSharp Diagnostics Toolkit for Log4Net and NLog add log4net and nlog as the supported backends.
The Using directives are a part of the plug-in model, allowing PostSharp to use external services. In this case, there are two entries (additional entries are added by other toolkits), the default, which is a required entry, and a (relative) path to the actual weaver implementation of our toolkit. At build time, PostSharp looks for project configurations in the referenced DLLs.
The Tasks section specifies a key feature of the XML configuration – the XML Multicasting. Like regular aspect multicasting, that is, the ability to apply a single aspect to multiple elements, XML Multicasting allows you to define aspect multicasting declaratively via XML. The XmlMulticast task will look for the data island with the name XmlMulticast, instantiate and apply the aspects that are specified within.
Which brings us to the actual LogAttribute aspect, that is shipped with the toolkits. This is a custom MethodLevelAspect, that is defined in the assembly PostSharp.Toolkit.Diagnostics.dll. The two entries in the XML file above define that the aspect will be applied by default to a) all methods in all types of the current assembly and b) will ignore property getters and setters. These lines are equivalent to applying the aspect on assembly level in code:
[assembly: Log]
[assembly: Log(AttributeExclude="true" AttributeTargetMembers="regex:get_.*|set_.*")]
You can limit the multicasting by using the regular PostSharp filters, such as AttributeTargetTypes.
Logging Options
To control the logging level, severity and granularity of the logging, the Diagnostics toolkits include several options for fine-grained control over the logging output:
OnEntryLevel/OnSuccessLevel/OnExceptionLevel – specifies the logging level (severity) of the Entry/Exit/Exception message (e.g. “Entering: MyType.MyMethod()/Leaving: MyType.MyMethod()”)
Possible values:
- None – the message will not be logged
- Debug – the message will be logged at Debug/Trace level (when applicable)
- Info – the message will be logged at Info level
- Warning – the message will be logged at Warn level
- Error – the message will be logged at Error level
- Fatal – the message will be logged at Fatal level
OnEntryOptions/OnSuccessOptions – sets options for logging parameters and return values.
The options include:
- None – no parameter information will be included
- IncludeParameterType – includes the type name of the parameter
- IncludeParameterName – includes the name of the parameter
- IncludeParameterValue - Includes parameter value, by calling
ToString on the object instance
- IncludeReturnValue – includes the return value (applicable on OnSuccessOptions only)
- IncludeThisArgument – includes the value of
this argument in an instance method
The default values for the different options are:
| Option Name |
Default Value |
| OnEntryLevel |
Debug |
| OnSuccessLevel |
Debug |
| OnExceptionLevel |
Warning |
| OnEntryOptions |
IncludeParameterType, IncludeParameterName, IncludeParameterValue |
| OnSuccessOptions |
IncludeParameterType, IncludeReturnValue |
| OnExceptionOptions |
None (exception is printed using the OnExceptionLevel severity) |
Examples:
Suppose we have a method Reverse in class StringUtils, that takes in a string and returns a reversed string. With the default settings, using NLog as the backend, our call to this method with the word “orange” will be logged like this:
...
TRACE Entering: MyApplication.StringUtils.Reverse(System.String input = "orange")
TRACE Leaving: MyApplication.StringUtils.Reverse(System.String) : "egnaro"
...
In the Entering line, the method signature contains the type name (System.String), the parameter name (“input”) and its value. The Leaving line contains only the parameter type and the return value.
Let’s look at another example. Suppose you have a class Customer, implementing an Active Record pattern, located in the namespace MyApplication.Data. Suppose we want to log all calls made to methods in this namespace with the Info level, and having the value of the instance (this argument) printed in the log output together with the value of the parameters. Simply add the following line to the .psproj file:
<LogAttribute
xmlns="clr-namespace:PostSharp.Toolkit.Diagnostics;assembly:PostSharp.Toolkit.Diagnostics"
AttributeTargetTypes="MyApplication.Data.*"
OnEntryLevel="Info"
OnSuccessLevel="Info"
OnEntryOptions="IncludeThisArgument | IncludeParameterValue" />
You can find additional configuration examples in the test projects of the PostSharp Diagnostics Toolkit source code.
Additional notes
In the toolkits we’re done away with manually specifying the ordering using AttributePriority – the value is now generating automatically during compilation, so be aware that ordering of the XML elements matters.
As always, we’d like to get your feedback on our Support Forums for PostSharp Toolkits! If you have suggestions, issues, or any other feedback, please let us know about it!
We hope that you’ll enjoy using the PostSharp Toolkits as much as we enjoy building them!
Happy PostSharping!
-Igal
Last Thursday, our PostSharp MVP Yan Cui joined us for an awesome webinar about how to use AOP to get near-realtime performance information from their servers running in the Amazon Cloud, using AWS CloudWatch.
The video and slides from the live webinar are now online for your viewing pleasure:
And here are the slides:
In the second part of the webinar I give a sneak peek at the PostSharp Diagnostic Toolkit. Download and install it today via NuGet, or get the source code on Github.
Happy PostSharping!
-Igal
We have just released an update for the PostSharp Diagnostics Toolkit – Log4Net and System.Diagnostics.Trace now join NLog and System.Console as the supported logging frameworks.
What does this mean for you? It means that you can now add logging to your application without any code changes – just by downloading a NuGet package:
- For System.Diagnostics.Trace support:
We have changed the NuGet package name a bit to make it more readable, and made the version number match that of the PostSharp build the package depends upon.
As I mentioned in the previous blog post, the NuGet package creates a .psproj file in the project’s directory named after the project. This is an XML file, which contains the configuration that is processed by PostSharp during compilation. I will go into much greater detail about the XML configuration in the next blog post.
As always, the source code for the PostSharp Toolkits is available on Github. Your feedback is very appreciated – please tell us your suggestions and issues on our Support Forums for PostSharp Toolkits.
Happy PostSharping!
-Igal
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Last week we were honored to have our friends at IdeaBlade join us for a very special webinar, dealing with real world AOP usage. Ward Bell, V.P. of Technology at IdeaBlade, did an excellent job of demonstrating how Aspect-Oriented Programming and PostSharp helps creating clutter-free data access, using their flagship product, DevForce.
DevForce uses PostSharp to infuse “Code First” entity model classes - entities like Customer and Order – with rich behaviors that go way beyond property change notification. You write entities with simple getters and setters; after PostSharp, they support property validation, entity navigation, lazy loading, dirty tracking, and UI data binding.
Here is the recorded webinar and the slides for your viewing pleasure! You can download the source code for the demo application and the slides from the IdeaBlade Documentation site.
Q&A
During the webinar you have asked us great questions, and, as promised, here are the answers to all of them:
Q: Does DevForce integrate with PostSharp?
A: Yes, DevForce Code First is built with PostSharp, so you don’t need a PostSharp to use it!
Q: Does any entity with a FirstName property get that clown verifier, or just Employee?
A: Just the Employee. As you can see, the type of the entity is passed into the custom verifier:
Q: Is it possible to step through the injected behaviors?
A: Yes, if you have the requisite symbol files (pdb files) loaded. It is rare to want to step through either the PostSharp or DevForce code itself, though. You’re usually debugging your own code, such as the “NoClownsVerifier”.
Q: Can you show some of the code in IdeaBlade.Aop?
A: Here is the definition for the two aspects provided by DevForce:
As you can see, it uses PostSharp’s abilities to introduce, or inject, behaviors at compile-time to the target classes, so it implements things like INotifyPropertyChanged for you in your entities automatically!
Please note that the specific behaviors we have injected may or may not be enabled when the entity is detached. For example, entity navigation properties require the EntityManager to locate the related entities in cache or query them from the database if necessary. Validation triggered by property setting requires an attached validation engine (our VerifierEngine) which is made available to the entity instance via its attached EntityManager. Accordingly, DevForce only enables these behaviors when the entity is attached. The capability has been injected, the code has been woven into the class, but the feature is turned off for detached entities.
Q: If you add your own properties to POCO class do you need to somehow tell PostSharp not to interfere with it?
A: The [Unmapped] attribute tells DevForce (and Entity Framework) that this property is NOT mapped to a column in the database and is not persisted. DevForce won’t activate the injected behaviors for such properties either (although we are considering an attribute that would tell DevForce to enable some of the behaviors for non-persistent properties in a future release).
Q: Can you provide you own base class for navigation property collections?
A: You can take over the behavior of any property, including navigation properties, via DevForce “property interceptors”, another feature that PostSharp weaves into your entity properties. Interceptors can be specified in the entity, in the base class, or in a separate property interceptor provider that DevForce will discover (we never require a base class in Code First).
Q: How do you mark a property to not have a specific aspect apply to it?
A: If this is a PostSharp question, the answer is “it’s up to how you implement your aspects.”
The DevForce aspects are applied at the class level but you can opt out at the property level with the [Unmapped] attribute. We only have two aspects (one for entities, one for complex objects) so I think what you’re asking is about opting out of one or more of the interfaces. DevForce lets you inject your own custom behavior into our interface implementations so you can do coarse grain or fine grained alterations of our implementations.
Q: How were the Employee.cs, Customer.cs and other table classes created?
A: I could have written them entirely by hand. I found that boring so I used what we call our “Code Second” technique. I pointed the EF Designer at the database and asked it to generate code with our “Code First” T4 code generator. Then I threw away the EDMX and went to town, cleaning out anything I didn’t like in the generated entity classes. What you see is what I decided to keep.
Q: How do you convert an existing “Database First” to the code-first model?
A: You might try the Code Second technique that I described above.
Q: How is the raising change notification done on the FullName property in the Employee class?
A: I used DevForce property interception feature which is also woven into the properties via AOP. I added the following code at the bottom of the Employee class:
DevForce recognizes this as an Employee property interceptor for FirstName and LastName. The implementation raises PropertyChanged when either of those properties has finished setting its value.
We are considering the possibility of automating discovery of FullName’s dependence upon FirstName and LastName but that capability is not in this release.
Final words
We hope that you enjoyed this very special webinar! If you have any more questions about how to use PostSharp, please visit our Support Forums to have them answered. For more information about DevForce and IdeaBlade, please visit their website.
We thank Ward Bell and IdeaBlade for the wonderful presentation and the Q&A! See you all next time!
Until then,
Happy PostSharping!
-Igal
Since its inception, PostSharp had always allowed making Aspect-Oriented Programming in .NET easy, allowing developers to produce cleaner code, encapsulating infrastructure code behind reusable modules.
We are pleased to announce today that we are making this even easier – with PostSharp Toolkits!
What are PostSharp Toolkits?
PostSharp Toolkits are a collection of ready-made solutions for adding common infrastructure code, such as logging, exception handling and performance monitoring to your application with no changes to your source code! Powered by PostSharp, the most complete AOP solution for .NET, the PostSharp Toolkits build upon the raw power of Aspect-Oriented Programming to seamlessly apply those solutions throughout your application.
Sounds interesting, how does it work?
We have great examples on how to add things like logging, tracing, and exception handling to your code. We’ve built upon this knowledge, and added things like XML-configuration, so no changes in the source code are required! Simply grab the toolkit from NuGet, and you’re all set!
What toolkits currently exist?
With the first release, we’re introducing the PostSharp Diagnostics Toolkit – an instrumentation toolkit that adds diagnostics features, such as logging, exception handling, performance counters and feature tracking to your application. The PostSharp Diagnostics Toolkit includes pluggable support for the leading logging frameworks, such as NLog. Support for additional frameworks is coming soon!
Note: As this is a work in progress, the PostSharp Diagnostics Toolkit currently only has logging support, with a very limited feature set. In the following releases, we will introduce additional configuration options, support for popular frameworks and other cool stuff!
The source code for the PostSharp Toolkits is available on GitHub, and we’re going to introduce new features based on your feedback in short release cycles.
Getting started
Here is how to add logging to your application without changing a single line of code:
Starting with a simple project:
- Step 1: Add the PostSharp Diagnostics Toolkit from NuGet to the assembly you wish to instrument. It downloads PostSharp automatically as a dependency (please note that you need PostSharp 2.1 SP1 or higher for the PostSharp Toolkits).
- Step 2: Rebuild your application
When you now run your application, this is what is printed in the output:
How did this happen?
The NuGet installation creates a .psproj file named after the current project in the source tree. This is an XML file, containing the configuration, which is processed by PostSharp during compilation.
The details about the XML configuration will be posted on GitHub. For now, just note that in the <Data> section there is a definition of LogAttribute. This is equivalent of placing the LogAttribute (part of the toolkit) on an assembly level in the source code, via:
[assembly: LogAttribute]
By default, it will be applied to all methods of the application. You can use the Filtering Properties to limit the multicasting. Please refer to the Online Documentation for details.
If we take a look at the compiled assembly in our favorite decompiler, we can see that the output lines were added directly in the method bodies, and no reference to PostSharp.dll is required!
What about writing the output to a file?
Glad you asked! The PostSharp Diagnostics Toolkit for NLog is exactly the solution for writing the output to NLog. Install it from NuGet, it will download all the required dependencies automatically. You will then need to configure NLog (either manually, or by downloading a NuGet package NLog.Configuration, which contains a sample configuration file for NLog). Then simply rebuild your application, and NLog will be automatically added to it!
Few notes:
The PostSharp Toolkits project is built using the PostSharp SDK. The PostSharp SDK is completely unsupported and undocumented, for the reasons detailed in this blog post. While the source code is available on GitHub, any questions pertaining to the PostSharp SDK will go unanswered.
The PostSharp Toolkits is an ongoing project, we are aiming at short (2-week) release cycles, bringing you more features based on your feedback!
Questions? Suggestions? Bugs?
Please visit our dedicated PostSharp Toolkits Support Forum to let us know what you think!
Happy PostSharping!
-Igal
Boilerplate code. It’s all around us, polluting our business logic, and forcing us to write the same code over and over again. Join us on Thursday, January 26th, as our very own Igal Tabachnik shows you how to stay DRY (Don’t-Repeat-Yourself) by using aspect-oriented programming (AOP) and PostSharp to remove boilerplate code that’s duplicated in and across systems.
Attendees will learn:
- Why the DRY principle matters
- How AOP helps to remove boilerplate code
- How to use PostSharp to produce cleaner code
- Real-world AOP usage examples
Oh, and that’s not all – we’re giving away two PostSharp licenses to two lucky attendees!
So hurry up, sign up here: https://www3.gotomeeting.com/register/724468246
During compilation, PostSharp takes great care in making sure that everything works correctly. When something goes wrong, PostSharp will report it as an error or a warning. Until now, however, whenever an error or a warning occurred, the developer had to manually navigate to that place in code.
We are excited to announce that with PostSharp 2.1 we’ve enhanced the errors and warnings with the exact location information, allowing you to simply double-click on the message and you’ll be taken to the error line!
To enable this feature, go to Tools – Options – PostSharp, and under Experimental, set Resolve Message Location to True:
Then, simply rebuild your solution, and if there are any warnings or errors, you’ll be able to see exactly where they are:
This is accomplished by specifying the member (in this case, the method) that is responsible for the message, in the aspect’s CompieTimeValidate method:
// Validate the attribute usage.
public override bool CompileTimeValidate( MethodBase method )
{
// Don't apply to constructors.
if ( method is ConstructorInfo )
{
Message.Write( method, SeverityType.Error, "CX0001",
"Cannot cache constructors." );
return false;
}
MethodInfo methodInfo = (MethodInfo) method;
// Don't apply to void methods.
if ( methodInfo.ReturnType.Name == "Void" )
{
Message.Write( method, SeverityType.Error, "CX0002",
"Cannot cache void methods." );
return false;
}
// Does not support out parameters.
ParameterInfo[] parameters = method.GetParameters();
for ( int i = 0; i < parameters.Length; i++ )
{
if ( parameters[i].IsOut )
{
Message.Write( method, SeverityType.Error, "CX0003",
"Cannot cache methods with return values." );
return false;
}
}
return true;
}
Aspect developers are encouraged to include the member in error/warning messages. For more information, please refer to the documentation on Working with Errors, Warnings and Messages.
Please note that this is not enabled by default as it is still experimental and might have an impact on performance. Please let us know how it works out for you!
Happy PostSharping!
-Igal
As most of you know, PostSharp’s transformation (weaving) of aspects into your assemblies happens after the compilation. One of the most requested features is the ability to see the actual code that is produced by PostSharp. Until now, you had to manually open the newly compiled assembly in your favorite decompiler to see the produced code.
We are delighted to announce that we’ve made viewing the source code in your favorite decompiler much easier – via a single click on the enhanced class or method:
By clicking the See enhanced source code link for the first time, you will be asked to select the decompiler you want to use (we currently support dotPeek, ILSpy and Reflector). You can always change the decompiler later from Tools – Options – PostSharp:
From now on, when you click on the See enhanced source code, your chosen decompiler will open and show you exactly the source code, as it was modified by PostSharp!
This feature is available in the latest version of PostSharp!
Happy PostSharping!
-Igal
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