C# 4 and .NET 4

338 ❘ ChaPTer 14 reflectiOn
can download from the Wrox web site at www.wrox.com) as a combined Visual Studio solution, as discussed
in Chapter 16, “Visual Studio 2010.” The download includes the required Visual Studio 2010 solution files.
The Whatsnewattributes library assembly
This section starts with the core WhatsNewAttributes assembly. The source code is contained
in the file WhatsNewAttributes.cs, which is located in the WhatsNewAttributes project of the
WhatsNewAttributes solution in the example code for this chapter. The syntax for doing this is
quite simple. At the command line, you supply the flag target:library to the compiler. To compile
WhatsNewAttributes, type the following:
csc /target:library WhatsNewAttributes.cs
The WhatsNewAttributes.cs file defines two attribute classes, LastModifiedAttribute and
SupportsWhatsNewAttribute. The attribute LastModifiedAttribute is the attribute that you can
use to mark when an item was last modified. It takes two mandatory parameters (parameters that are
passed to the constructor): the date of the modification and a string containing a description of the changes.
There is also one optional parameter named issues (for which a public property exists), which can be
used to describe any outstanding issues for the item.
In practice, you would probably want this attribute to apply to anything. To keep the code simple, its usage
is limited here to classes and methods. You will allow it to be applied more than once to the same item
(AllowMultiple=true) because an item might be modified more than once, and each modification will
have to be marked with a separate attribute instance.
SupportsWhatsNew is a smaller class representing an attribute that doesn’t take any parameters. The
idea of this attribute is that it is an assembly attribute that is used to mark an assembly for which you are
maintaining documentation via the LastModifiedAttribute. This way, the program that will examine
this assembly later on knows that the assembly it is reading is one on which you are actually using your
automated documentation process. Here is the complete source code for this part of the example:
using System;
namespace WhatsNewAttributes
{
[AttributeUsage(
AttributeTargets.Class | AttributeTargets.Method,
AllowMultiple=true, Inherited=false)]
public class LastModifiedAttribute: Attribute
{
private readonly DateTime _dateModified;
private readonly string _changes;
public LastModifiedAttribute(string dateModified, string changes)
{
dateModified = DateTime.Parse(dateModified);
changes = changes;
}
public DateTime DateModified
{
get { return dateModified; }
}
public string Changes
{
get { return changes; }
}
public string Issues { get; set; }
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