c# generate barcode from string Reflection in C#.NET

Creating QR in C#.NET Reflection

14

The Module class can be used to retrieve or search for types contained within a specified module. For assemblies originally written in languages that support the notion of modules (for example, Visual Basic), it also supports GetField, GetFields, GetMethod, and GetMethods methods. In those types of modules, fields and methods can be attached directly to a module. In Lesson 3, you ll learn more about how to use reflection on fields and methods.

In this lab, you will create a console application that creates two instances of the Assembly class and shows some of its properties. If you encounter a problem completing an exercise, the completed projects are available on the companion CD in the Code folder. 1. Create a new console application, and call it AssemblyDemo. 2. Add an include statement (or the Imports statement for Visual Basic) to the System.Reflection namespace to the main code file. 3. Create a new static method called ShowAssembly that takes an instance of the Assembly class as a parameter. 4. Inside the new ShowAssembly method, write out the FullName, GlobalAssemblyCache, Location, and ImageRuntimeVersion properties to the console. 5. Next iterate through each of the Modules in the Assembly, and show each module s name in the console. 6. In the main method of the project, load the System.dll assembly from the framework directory under the Windows directory using the Assembly.Load method. 7. Call the ShowAssembly method with the new assembly instance. 8. Create a new instance of the Assembly class by getting the currently executing assembly. 9. Call the ShowAssembly method again with this instance of the Assembly instance from the executing assembly. Your code might look something like this:

' VB Imports System.Reflection Class Program Public Shared Sub Main(ByVal args() As String) Dim path As String = _ "C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.dll"

' Load a specific Assembly Dim a As Assembly = Assembly.LoadFile(path) ShowAssemblyInfo(a) ' Get our Assembly Dim ourAssembly As Assembly = Assembly.GetExecutingAssembly ShowAssemblyInfo(ourAssembly) Console.Read() End Sub Shared Sub ShowAssemblyInfo(ByVal a As Assembly) Console.WriteLine(a.FullName) Console.WriteLine("From GAC {0}", a.GlobalAssemblyCache) Console.WriteLine("Path: {0}", a.Location) Console.WriteLine("Version: {0}", a.ImageRuntimeVersion) ' Show Modules For Each m As [Module] In a.GetModules Console.WriteLine(" Mod: {0}", m.Name) Next Console.WriteLine() End Sub End Class // C# using System.Reflection; class Program { static void Main(string[] args) { string path = @"C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.dll"; // Load a specific Assembly Assembly a = Assembly.LoadFile(path); ShowAssemblyInfo(a); // Get our Assembly Assembly ourAssembly = Assembly.GetExecutingAssembly(); ShowAssemblyInfo(ourAssembly); Console.Read(); } static void ShowAssemblyInfo(Assembly a) { Console.WriteLine(a.FullName);

14

Console.WriteLine("From GAC {0}", a.GlobalAssemblyCache); Console.WriteLine("Path: {0}", a.Location); Console.WriteLine("Version: {0}", a.ImageRuntimeVersion); // Show Modules foreach (Module m in a.GetModules()) { Console.WriteLine(" Mod: {0}", m.Name); } Console.WriteLine(); } }

10. Build the project, and resolve any errors. Verify that the console application successfully shows both the assemblies and their modules.

Assemblies are containers for modules, and modules are containers for types. To access assemblies that are related to the currently running code, load ad-hoc assemblies, and list the modules in an assembly, use the Assembly class.

You can use the following questions to test your knowledge of the information in Lesson 1, Understanding Reflection. The questions are also available on the companion CD if you prefer to review them in electronic form.

Answers to these questions and explanations of why each answer choice is right or wrong are located in the Answers section at the end of the book.

1. What static method of the Assembly class is guaranteed to return an instance that represents the assembly that contains the startup object (or entry point) of the application A. Assembly.GetCallingAssembly B. Assembly.GetExecutingAssembly C. Assembly.GetEntryAssembly D. Assembly.Load

2. Which statements are true when referring to an assembly and module (Choose all that apply.) A. An assembly can contain one or many other assemblies. B. An assembly can contain one or many modules. C. An assembly can directly contain types. D. A module can directly contain types.