This past weekend I presented the topic "Intro to Dependency Injection and Inversion of Control" at the Phoenix Desert Code Camp. A big thank you goes out to everyone who attended. It was such a popular topic that it actually moved up to the largest room in the conference location, the Theater at UAT! Thanks again everyone!

At the bottom of this post are the resources from this presentation.

Resolution from Error During the Presentation

For those of you were present when I ran into an issue with this "DynamicMethod" error, I have figured out the issue. It's a bug in Unity. It looks like its been fixed and should be available in the next release.

I was able to work around this issue by moving the Dependency attribute into the Interface. I have updated the code in the download below to reflect this.

Presentation Resource Download

Full Solution Download (900K)

PowerPoint Presentation

You can also view the presentation online - located here.

Note: A full solution is supplied at the bottom of this post if you would like to download it and run it.

A couple of days ago Matt wrote about the new Unity Application Block. The Unity MSDN article describes Unity as:

The Unity Application Block (Unity) is a lightweight, extensible dependency injection container. It facilitates building loosely coupled applications and provides developers with the following advantages:

• Simplified object creation, especially for hierarchical object structures and dependencies
• Abstraction of requirements; this allows developers to specify dependencies at run time or in configuration and simplify management of crosscutting concerns
• Increased flexibility by deferring component configuration to the container
• Service location capability; this allows clients to store or cache the container

Designing a software system architecture with loosely coupled components makes life easier in the long run. A few of the benefits of loose coupling are : maximizing testability, modularizing components, and increase the maintainability of the code.

This is a simple introduction into Unity that exemplifies the simplicity of the container setup. I will cover two options for type registration:

1. Manual Method based type Registration
2. Configuration file (XML Based) type Registration

The Example Application

The application that is included at the bottom of this post is visualized via the class diagram below. This simple application utilizes very simple implementations of the repository, mapper, domain model, data transfer object (DTO) and service layer patterns for example purposes.

The application follows a very simple flow as shown below:

The console application calls into the Service layer which calls into the repository to get the data which calls into the DB. A domain object is created from the Repository call, which is passed up to the service layer. The Service layer returns a DTO via the DTO Mapper to the parent caller (the console app) and then the console app displays the customer name via a write line call.

None of these layers have any inter-dependent dependencies coded inside of them. I'm using constructor injection to inject dependencies into the calling object.

Once unity is set up, it will find the dependencies and supply them to the program at runtime. Therefore, if I need a ICustomerRepository for the service layer to work properly, Unity will give the Service layer a CustomerRepository instance. Since CustomerRepository inherits from ICustomerRepository Unity is able to make this link (once you've set it up) and supply the proper instance.

Class Diagram

The Setup & Code

The easiest way to see HOW Unity works is to get into the code. My recommendation is to download the sample below, fire it up in Visual Studio and set some break points to see how the code is interacting. Seeing is believing!

Before Unity can supply your application types at runtime, you have to tell Unity WHAT you want it to supply and where to find it. This can be done multiple ways as described here. Today we will go over manual configuration inside of the console app, and xml configuration.

Manual Configuration

The manual configuration that I've utilized here utilizes the fluent interface of the container.

Explanation of code: Here we are telling Unity to register a type. We're saying "If someone requests ICustomerRepository, give them an instance of CustomerRepository. If someone requests ICustomerDTOMapper, then give them an instance of CustomerDTOMapper. ..." and so on.

Using the Container From Manual Configuration

After you've set up the types of objects the container should resolve, you can then ask the container for a instance of "ICustomerService" and then invoke a method call on it. At this very point in time Unity will give you the CustomerService, and then when the customer service needs a repository Unity will then give it a instance of CustomerRepository, etc. At this point in time, everything is mapped for you behind the scenes. The only thing you have to do is ask for the first object and Unity will walk the dependency graph and fill in the blanks for you (if as long as you've given Unity the proper types it needs).

Here's how to do this in the code:

XML Configuration

XML configuration utilizes an external XML file (app.config/web.config) to create its dependency graph. This allows for a lot more freedom in what you would like to do with your app. If you're not happy with a certain version of "ICustomerRepository" you can create a new one, drop the DLL in the bin folder and change this config file to point to the new one and you're done. No recompiling!

In this implementation I'm using the app.config file because this is a Console App for example purposes. The full schema for XML configuration can be found here on the MSDN.

To utilize the XML configuration you'll need to utilize a custom config section. You can do this by placing this code into your config section of your app.config file:

Next, you'll need to add the container and type definition as shown below (this is just a snippet, full code is included at the bottom of the post):

The container gets its types from the config file at runtime.

Each type is declared in the config file as the "type" of object to find and the "mapTo" defines which object to return when the "type" is requested.

The type definitions are declared as type, assembly.

Using the Container From XML Configuration

To force Unity to use the XML Configuration you have to perform few extra set up steps in the application code as shown below. Essentially you're telling Unity that it's configuration/mappings are stored in a config file. The config section configures the container for you, as shown below.

To have Unity resolve an instance, its the same as the manual configuration option above. Here is the same image from above that displays how to do this:

Conclusion

Overall, using Unity as quite simple for this example. The docs on MSDN were pretty good, however I didn't really like the examples that were contained with the download because they did not show you how to utilize XML configuration as I wanted to. It didn't take but a few minutes to figure out what I needed to do. I think Unity is a decent solution at this time. I plan to investigate further into the depths of Unity to see if it may possibly be an alternative for my favorite container tool, Windsor Container.

Download The Code For This Post

FooTheory.UnityExample.zip (~477K)

Rhino Mocks and NUnit both have a "Is" keyword, both used for a fluent style of syntax. Unfortunately this causes testing problems when you need to use them together. The .NET compiler can only understand one "Is" keyword at a time. We can't use both unless we full qualify the second one.

Having said that, I've fully qualified the "Is" keyword for Rhino Mocks and NUnit before and I find it clunky and I feel its a code smell to me.

In the figure below an example of a fully qualified "Is" keyword for Rhino Mocks is declared.

 1 [Test]
 2 public void ExampleTest()
 3 {
 4     // ... items ommited for brevity
 5     
 6     With.Mocks(mockery)
 7     .Expecting(delegate
 8     {
 9        Expect.Call(databaseMock.GetStoredProcCommand(null))
10            .IgnoreArguments()
11            .Constraints(Rhino.Mocks.Constraints.Is.NotNull())
12            .Return(databaseCommandStub); 
13     })
14     .Verify(delegate
15     {
16         IQuery query = ExampleResultQuery.GetInsertResultQueryFrom(someparameter);
17         IDatabaseCommand command = query.PrepareCommandUsing(databaseMock);
18         Assert.That(command, Is.SameAs(databaseCommandStub)); 
19     }); 
20 }

On line 11, we can see the fully qualified name: Rhino.Mocks.Constraints.Is.NotNull() method called.

This, my friends, is a code smell (IMO).

How To Fix

The NUnit testing framework provides a "Iz" syntax helper that VB.NET developers use because "Is" in VB.NET is a keyword.

Since we're using .NET Managed code we can use the Iz keyword and it will achieve the same results as Is did. Therefore we can use the Is keyword in Rhino Mocks and we can use the Iz keyword in NUnit. This saves a lot of key strokes over the course of a day.

Final Example:

 1 
 2 [Test]
 3 public void ExampleTest()
 4 {
 5     // ... items ommited for brevity
 6     
 7     With.Mocks(mockery)
 8     .Expecting(delegate
 9     {
10        Expect.Call(databaseMock.GetStoredProcCommand(null))
11            .IgnoreArguments()
12            .Constraints(Is.NotNull())
13            .Return(databaseCommandStub); 
14     })
15     .Verify(delegate
16     {
17         IQuery query = ExampleResultQuery.GetInsertResultQueryFrom(someparameter);
18         IDatabaseCommand command = query.PrepareCommandUsing(databaseMock);
19         Assert.That(command, Iz.SameAs(databaseCommandStub)); 
20     }); 
21 }

Please note: Line 12 has the normal "Is.NotNull()" call from Rhino Mocks, and Line 19 utilizes the Iz syntax helper from NUnit.

I find this much easier on the wrist. :)

That's right! I will be presenting at the Phoenix Arizona Desert Code Camp on May 31st 2008.

I will be presenting a course on Dependency Injection / Inversion of Control. The time's have not been posted yet but as I find out more information I will update this blog.

I hope to see you there. Click here to sign up for the code camp.

First off, yes, I know there are other tutorials on how to watermark PDF's with iTextSharp. Unfortunately none of them showed me exactly what I wanted to do - which is why I wrote this one.

Currently I'm involved with a project that utilizes PDF's as their main product - a legal document. When I arrived to this client they utilized iTextSharp to "watermark" their PDF's. I've been wanting to get my hands dirty with iTextSharp for awhile now. So I cracked open the code base one weekend to see how they were watermarking the PDF's. After poking around for about 2 minutes I saw how they were performing the "watermarking" and unfortunately it was not the best way to get the job done.

Problems with current implementation:

• Images were used to write text.
  • Huh? An image with text was "underlain" into the PDF. The image had faded text that when inside of the finished product, looked watermarked. The image would say things similar to "Sample". The entire image looked like this:
  • 
• The watermark orientation would always end up as Portrait.
  • This was because the watermark was an image and it was created for a portrait and it was coded to never detect the page orientation. If the page was landscape the watermarked page would look like this:
  • 
• The watermarked text could never be changed.
  • Well, it could be, but it took a code change. The images were kept as resources in the library. So if they needed a new watermark, that meant a code change, testing and a redeploy.

So How Do We Fix This? What's the End Goal?

• We want to be able to watermark the PDF document with Text, not images.
• The code should detect page orientation.
• We should be able to watermark the PDF with text that we provide at run time.

Current Document	Expected Result
A Non watermarked document	A watermarked document (red is below the text)

The Solution

I'm very amazed with iTextSharp's ability to manipulate PDF's. From existing PDF's to new PDF's to content extraction, iTextSharp does it all. The best part about it is... ITS FREE (other than your development time, that is).

I've created a solution which I provide the download link for at the bottom of the post, but for now here's the code that does the dirty work:

FooTheoryPdf.cs

 1 using System.IO;
 2 using System.Text;
 3 using iTextSharp.text;
 4 using iTextSharp.text.pdf;
 5 
 6 namespace FooTheory.iTextSharpLibrary
 7 {
 8     /// <summary>
 9     /// Example PDF Class
10     /// </summary>
11     public class FooTheoryPdf
12     {
13         /// <summary>
14         /// Method that will utilize iTextSharp to write the <see cref="stringToWriteToPdf"/> to the 
15         /// pdf on each page of the PDF.
16         /// </summary>
17         /// <param name="sourceFile">The PDf File</param>
18         /// <param name="stringToWriteToPdf">The text to write to the pdf</param>
19         /// <returns>The bytes of the newly updated PDF with <see cref="stringToWriteToPdf"/> in the pdf.</returns>
20         public static byte[] WriteToPdf(FileInfo sourceFile, string stringToWriteToPdf)
21         {
22             PdfReader reader = new PdfReader(sourceFile.FullName);
23 
24             using (MemoryStream memoryStream = new MemoryStream())
25             {
26                 //
27                 // PDFStamper is the class we use from iTextSharp to alter an existing PDF.
28                 //
29                 PdfStamper pdfStamper = new PdfStamper(reader, memoryStream);
30 
31                 for (int i = 1; i <= reader.NumberOfPages; i++) // Must start at 1 because 0 is not an actual page.
32                 {
33                     //
34                     // If you ask for the page size with the method getPageSize(), you always get a
35                     // Rectangle object without rotation (rot. 0 degrees)—in other words, the paper size
36                     // without orientation. That’s fine if that’s what you’re expecting; but if you reuse
37                     // the page, you need to know its orientation. You can ask for it separately with
38                     // getPageRotation(), or you can use getPageSizeWithRotation(). - (Manning Java iText Book)
39                     //   
40                     //
41                     Rectangle pageSize = reader.GetPageSizeWithRotation(i);
42 
43                     //
44                     // Gets the content ABOVE the PDF, Another option is GetUnderContent(...)  
45                     // which will place the text below the PDF content. 
46                     //
47                     PdfContentByte pdfPageContents = pdfStamper.GetUnderContent(i);
48                     pdfPageContents.BeginText(); // Start working with text.
49 
50                     //
51                     // Create a font to work with 
52                     //
53                     BaseFont baseFont = BaseFont.CreateFont(BaseFont.HELVETICA_BOLD, Encoding.ASCII.EncodingName, false);
54                     pdfPageContents.SetFontAndSize(baseFont, 40); // 40 point font
55                     pdfPageContents.SetRGBColorFill(255, 0, 0); // Sets the color of the font, RED in this instance
56 
57 
58                     //
59                     // Angle of the text. This will give us the angle so we can angle the text diagonally 
60                     // from the bottom left corner to the top right corner through the use of simple trigonometry. 
61                     //
62                     float textAngle =
63                         (float) FooTheoryMath.GetHypotenuseAngleInDegreesFrom(pageSize.Height, pageSize.Width);
64 
65                     //
66                     // Note: The x,y of the Pdf Matrix is from bottom left corner. 
67                     // This command tells iTextSharp to write the text at a certain location with a certain angle.
68                     // Again, this will angle the text from bottom left corner to top right corner and it will 
69                     // place the text in the middle of the page. 
70                     //
71                     pdfPageContents.ShowTextAligned(PdfContentByte.ALIGN_CENTER, stringToWriteToPdf,
72                                                     pageSize.Width/2,
73                                                     pageSize.Height/2,
74                                                     textAngle);
75 
76                     pdfPageContents.EndText(); // Done working with text
77                 }
78                 pdfStamper.FormFlattening = true; // enable this if you want the PDF flattened. 
79                 pdfStamper.Close(); // Always close the stamper or you'll have a 0 byte stream. 
80 
81 
82                 return memoryStream.ToArray();
83             }
84         }
85     }
86 }

Then there is a small math library I created to get the angle of the text through some simple Trig.

FooTheoryMath.cs

 1 using System;
 2 
 3 namespace FooTheory.iTextSharpLibrary
 4 {
 5     /// <summary>
 6     /// Math library 
 7     /// </summary>
 8     public static class FooTheoryMath
 9     {
10         public static double GetHypotenuseAngleInDegreesFrom(double opposite, double adjacent)
11         {
12             //http://www.regentsprep.org/Regents/Math/rtritrig/LtrigA.htm
13             // Tan <angle> = opposite/adjacent
14             // Math.Atan2: http://msdn.microsoft.com/en-us/library/system.math.atan2(VS.80).aspx 
15 
16             double radians = Math.Atan2(opposite, adjacent); // Get Radians for Atan2
17             double angle = radians*(180/Math.PI); // Change back to degrees
18             return angle;
19         }
20     }
21 }

The Results

Utilizing a simple interface:

We're able to generate PDF's that are watermarked on an angle from bottom left corner to top right corner.

Here is a screen shot of what the generated PDF looks like:

Clicking the Top button:

Clicking the Bottom Button:

I'm able to change the message:

This will produce:

Conclusion

I found the iTextSharp quite versatile for working with PDF's. This solution will help you write text to existing PDF's quite easily.

Possible implementations include:

• Place this into a WCF service to create a watermarking service
• Leave it as it is, implemented as a class library.
• Create your own .NET PDF Client that you could sell (I've read somewhere - cant find the source - that a couple third party .NET PDF components are actually written on top of iTextSharp).

While working to accomplish what I have above I found the best reference for iTextSharp was actually the iText Book written by Bruno Lowagie. You can purchase it here on Amazon.com.

And Finally ... While writing this I kept thinking .....

Why would you want to watermark existing PDF's?

There are a few options.

1. Accountability: Lets say you have a ton of PDF's stored from a long running highly confidential report process and these PDF's are stored nightly/weekly on a certain directory. Perhaps you want to make sure that when a user logs in and accesses one of these highly confidential PDF's you water mark it with the users name on each page. Therefore, if it makes it into the hands of the media, you can see where/who it came from.
2. Licensing: Perhaps you main product is a PDF. Lets say you're a book publisher and you sell PDF versions of the book or you allow people who have already purchased the hard copy to download the PDF version.  What you can do is force the user to create a profile in order to download the PDF. Usually this also includes some type of security question like "turn to page 435 and give us the last word on the page" in order to validate the user actually HAS the book in hand. Once they are authorized to download the PDF book, you can watermark every page on the book with their name "Licensed to: <FirstName> <LastName>. Let's face it, people are MUCH less likely to give a PDF book away on Torrent or P2P software when every single page has their name on it. It's not the BEST method of licensing, but it works.
3. Other: Perhaps Company A is acquired by Company B and Company B wants to make sure that all PDF's on Company A's site are amended with the text "Company A is a subsidiary of Company B". What if company A has 15,000 PDF's that they have on their site? Maybe its a resume assistance site that has over 15,000 sample resumes. Are you going to open each PDF and do this by hand? Nope. Not at all. You can intercept the call for the PDF's and then write the text at the bottom before they're delivered to the end user.
4. The list could go on and on ...

Download The Code

FooTheory.iTextSharpLibrary.Example.zip (4.69 MB)