Runtime Type Information (Reflection) in C#.


This article has been excerpted from book "The Complete Visual C# Programmer's Guide from the Authors of C# Corner".

Reflection is the sole mechanism of discovering class information at runtime. You can create instances of classes on the fly at runtime using Reflection namespace members, which is similar to the optional Runtime Type Information mechanism in C++.

The ability to list a type's members is a great way to quickly discover which elements are available. It is an important tool for reporting on your system as well as assisting in the development of user documentation. Using the Reflection namespace, you can control what kind of members you want to show to your users, as well as other information (such as the visibility of a particular method). You can also get information on all of the members in a class or specify only certain subsets (such as methods or fields). Also you can use this neat feature when documenting class hierarchy.

Listing 5.76: Reflection.cs, Reflection Example


// example object creation factory

using
System;
using
System.Reflection;

// simple class

class
MyClass
{
    public static int x = 0;
    public void prompt(string param1)
    {
        Console.WriteLine("MyClass… " + param1);
    }

    public static void prompt2()
    {
        Console.WriteLine("Here is a message from prompt2.");
    }
}


class
TheApp
{
    public static void Main()
    {
        // create the Type object
        Type type1 = typeof(MyClass);

        //or
        // Type type1 = Type.GetType("MyClass");
        // create an instance of that type
        Object o = Activator.CreateInstance(type1);
        ((MyClass)o).prompt("hello1");

        // declare and populate the arrays to hold the information...
        FieldInfo[] fi = type1.GetFields(BindingFlags.Default |
        BindingFlags.Static |
        BindingFlags.NonPublic | BindingFlags.Public); // fields
        MethodInfo[] mi = type1.GetMethods(BindingFlags.Default |
        BindingFlags.Static |
        BindingFlags.NonPublic | BindingFlags.Public); // methods

        // iterate through all the method members
        foreach (MethodInfo m in mi)
        {
            Console.WriteLine(m);
        }

        // iterate through all the field members
        foreach (FieldInfo f in fi)
        {
            Console.WriteLine(f);
        }

        object[] argValues = new object[] { "Hello2" };
        String[] argNames = new String[] { "param1" };

        // call the requested method with filled parameters
        type1.InvokeMember("prompt", BindingFlags.Default |
        BindingFlags.InvokeMethod,
        null, o, argValues, null, null, argNames);
        Console.ReadLine();
    }
}


Figure 5.31 contains the resulting output.

Figure5.31.gif

Figure 5.31: Screen Output Generated from Listing 5.76

The reflection mechanism is also useful when developing applications that use third-party COM+ components at your site or in the market because you can use Reflection to accomplish late binding to COM objects via the IDispatch interface.

Conclusion

Hope this article would have helped you in understanding Runtime Type Information (Reflection) in C#. See other articles on the website on .NET and C#.

visual C-sharp.jpg The Complete Visual C# Programmer's Guide covers most of the major components that make up C# and the .net environment. The book is geared toward the intermediate programmer, but contains enough material to satisfy the advanced developer.