Reflection in C Sharp

Interactive Session on Reflection
In C Sharp
Classification: Restricted 2012-04-19

Reflection

•Reflection is the Feature that enables you to obtain the information about a type.
•All .NET assemblies have metadata information stored about the types defined in
modules. This metadata information can be accessed by mechanism called as
“Reflection”.
•Reflection is the ability of a managed code to read its own metadata for the purpose of
finding assemblies, modules and type information at runtime. In other words, reflection
provides objects that encapsulate assemblies, modules and types. A program reflects
on itself by extracting metadata from its assembly and using that metadata either to
inform the user or to modify its own behavior. Reflection is similar to C++ RTTI (Runtime
Type Information), but much broader in scope and capability

2 Classification: Restricted 2012-04-19

Reflection
Name Space to be used System.reflection

• When writing a C# code that uses reflection, the coder can use the type of operator
to get the object's type or use the GetType() method to get the type of the current
instance.
• Using reflection services, we are able to programmatically obtain the same
metadata information displayed by ildasm.exe.


Example of Reflection

• Using GetType to obtain type information:
C# Code :-

• int i = 42;
System.Type type = i.GetType();
System.Console.WriteLine(type);

• Output of this Code will be
System.Int32


When use Reflection

• If we want to know assembly information at run time ,then we use reflection.
Reflection are used for data binding in .NET Framework. It is also used for testing in
.NET Framework.


Example

• In the below example reflection is used to obtain the full name of a loaded
assembly:
CODE
System.Reflection.Assembly o = System.Reflection.Assembly.Load("mscorlib.dll");
System.Console.WriteLine(o.GetName());

Output of the above code
mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089


So Reflection allows you to

• Enumerate the members of a type
• Instantiate a new object
• Execute the members of an object
• Find out information about a type
• Find out information about an assembly
• Inspect the custom attributes applied to a type
• Create and compile a new assembly


System.Reflection Namespace


The System.Type Class

• The System.Type class defines a number of members that can be used to examine
a type’s metadata, a great number of which return types from the System.Reflection
namespace.
• Eg: Type.GetMethods() returns an array of MethodInfo types, Type.GetFields()
returns an array of FieldInfo types.


Members of System.Type
• IsAbstract
• IsArray
• IsClass
• IsCOMObject
• IsEnum
• IsInterface
• IsPrimitive
• IsNestedPrivate
• IsNestedPublic
• IsSealed
• IsValueType

• These properties allow you to discover a number of basic traits about the Type you are referring to
(e.g., if it is an abstract method, an array, a nested class, and so forth).


Methods
• GetConstructors()
• GetEvents()
• GetFields()
• GetInterfaces()
• GetMembers()
• GetMethods().
• GetNestedTypes()
• GetProperties()
• These methods allow you to obtain an array representing the items (interface, method,
property, etc.) you are interested in. Each method returns a related array (e.g.,
GetFields() returns a FieldInfo array, GetMethods() returns a MethodInfo array, etc.).
Each of these methods has a singular form (e.g., GetMethod(), GetProperty(), etc.) that
allows you to retrieve a specific item by name, rather than an array of all related items.


Methods

• GetType()
To obtain type information, you may call the static GetType() member of the
System.Type class and specify the fully qualified string name of the type to
examine.
Compile-time knowledge of the type to be extracted from metadata is not
required.


GET TYPE METHOD

• The Type.GetType() method has overloads to allow you to specify two Boolean
parameters, one of which controls whether an exception should be thrown if the
type cannot be found, and the other of which establishes the case sensitivity of the
string.
• Obtaining type information using the static Type.GetType() method:
• Type t = Type.GetType("CarLibrary.SportsCar", false, true);


Reflecting on Methods
• Type.GetMethods() returns an array of System.Reflection.MethodInfo types.

// Display method names of type.
public static void ListMethods(Type t)
{
Console.WriteLine("Methods");
MethodInfo[] mi = t.GetMethods();
foreach(MethodInfo m in mi)
Console.WriteLine("->{0}", m.Name);
Console.WriteLine("");
}


Reflecting on Fields

• Type.GetFields() returns an array of System.Reflection.FieldInfo types.

// Display field names of type
public static void ListFields(Type t)
{
Console.WriteLine("Fields");
FieldInfo[] fi = t.GetFields();
foreach(FieldInfo field in fi)
Console.WriteLine("->{0}", field.Name);
}


Reflecting on Properties
• Type. GetProperties() returns an array of System.Reflection. PropertyInfo types.

// Display property names of type.
public static void ListProps(Type t)
{
Console.WriteLine("***** Properties *****");
PropertyInfo[] pi = t.GetProperties();
foreach(PropertyInfo prop in pi)
Console.WriteLine("->{0}", prop.Name);
}


Dynamically Loading Assemblies

• The act of loading external assemblies on demand is known as a dynamic load.
• System.Reflection defines a class Assembly. Which enables to dynamically load an
assembly and discover properties about the assembly.
• Assembly type enables to dynamically load private or shared assemblies, as well as
load an assembly located at an arbitrary location.


Late Binding

• Late binding is a technique in which you are able to create an instance of a given
type and invoke its members at runtime without having compile-time knowledge of
its existence.
• It increases applications Extensibility.


Reflection in C #

Harman
Aplication Developer


Reflection in C Sharp

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