reflection and ado

8/8/2019 Reflection and Ado

1/38

Reflection and ADO. Net

Karthik Eetur


2/38

REFLECTION

Reflection is a way of getting information about anyspecific class or assembly at runtime. You can alsosay its RTTI (Runtime Type Information).

With the help of reflection you can get the all the

properties and methods with arguments/parameters.You can also get the list of classes, interfaces,structures and enumeration in an assembly by usingreflection.

You can dynamically create an instance of an objectat runtime and invoke methods dynamically.

examples of reflection: Object browser and VisualStudio .NET IDE (Integrated DevelopmentEnvironment)


3/38

Namespace: System. Reflection

The Reflection namespace contains

classes and interfaces that provide a

managed view of loaded types,

methods, and fields, with the ability to

dynamically create and invoke types.


4/38

Classes in Reflection

class AmbiguousMatchException The exception that is thrown when

binding to a method results in more

than one method matching the binding

criteria.

class Assembly Defines anAssembly, which is a

reusable, versionable, and self-

describing building block of a common

language runtime application.

class AssemblyAlgorithmIdAttribute Specifies an algorithm to hash all filesin an assembly. This class cannot be

inherited.

class AssemblyCompanyAttribute Defines a company name custom

attribute for an assembly manifest.


5/38

class AssemblyConfigurationAttribute Defines an assembly configuration

custom attribute (such as retail or debug)

for an assembly manifest.

class AssemblyCopyrightAttribute Defines a copyright custom attribute for

an assembly manifest.

class AssemblyCultureAttribute Specifies which culture the assemblysupports.

class AssemblyDefaultAliasAttribute Defines a friendly default alias for an

assembly manifest.

class AssemblyDelaySignAttribute Specifies that the assembly is not fullysigned when created.

class AssemblyDescriptionAttribute Defines an assembly description custom



6/38

class AssemblyFlagsAttribute Specifies whether an assembly

supports side-by-side execution on the

same machine, in the same process, orin the same application domain. This

class cannot be inherited.

class AssemblyInformationalVersionAttr

ibute

Defines an assembly informational

version custom attribute for an

assembly manifest.

class AssemblyKeyFileAttribute Specifies the name of a file containing

the key pair used to generate a shared

name.

class AssemblyName Fully describes an assembly's unique

identity.

class AssemblyNameProxy Provides a remotable version of the .

class AssemblyProductAttribute Defines a product name custom



7/38

class ConstructorInfo Discovers the attributes of a class

constructor and provides access to

constructor metadata.

class CustomAttributeFormatException The exception that is thrown when the

binary format of a custom attribute is

invalid.

class DefaultMemberAttribute Defines the member of a type that is

the default member used by

Type.InvokeMember. The default

member is a name given to a type.

class EventInfo Discovers the attributes of an eventand provides access to event

metadata.

class FieldInfo Discovers the attributes of a field and

provides access to field metadata.


8/38

class ManifestResourceInfo Contains manifest resource topology

information.

class MemberInfo Discovers the attributes of a member

and provides access to member

metadata.

class MethodBase Provides information about methods

and constructors.

class MethodInfo Discovers the attributes of a method

and provides access to method

metadata.

class Missing Represents a missing Object. This

class cannot be inherited.

class Module Performs reflection on a module.


9/38

class ParameterInfo Discovers the attributes of a parameter

and provides access to parametermetadata.

class Pointer Provides a wrapper class for pointers.

class PropertyInfo Discovers the attributes of a property

and provides access to property

metadata.class ReflectionTypeLoadException The exception that is thrown by the

Module.GetTypes method if any of the

classes in a module cannot be loaded.

This class cannot be inherited.

class StrongNameKeyPair Encapsulates access to a public orprivate key pair used to sign strong

name assemblies.

class TargetException Represents the exception that is

thrown when an attempt is made to

invoke an invalid target.


10/38

Interfaces & Structures in

Reflectioninterface ICustomAttributeProvider Provides custom attributes for reflection

objects that support them.

interface IReflect Allows objects to return MemberInfo

objects that represent an object.

structure InterfaceMapping Retrieves the mapping of an interface

into the actual methods on a class that

implements that interface.

structure ParameterModifier Attaches a modifier to parameters so

that binding can work with parameter

signatures in which the types have

been modified.

(refer document)


11/38

Loading Metadata of an Assembly

In the Entity Data Model (EDM), item collections areresponsible for loading metadata from persistentresources, such as XML files or common languageruntime (CLR) assemblies, and are in an instance ofthe MetadataWorkspace class

ADO.NET provides an ItemCollection class as a coreAPI for loading and holding in-memory metadata.

The ItemCollection has several derived classes,such as ObjectItemCollection, EdmItemCollection,StoreItemCollection, andStorageMappingItemCollection.

Each of these collection classes is specialized for adifferent type of metadata. The following sectionsexplain how these collection classes interact withdifferent types of metadata.


12/38

ObjectItemCollection:

The ObjectItemCollection class is responsible forloading metadata about the object model. The objectmodel represents the CLR classes that can be used as aprogrammatic realization of the conceptual model.

EdmItemCollection:

An EdmItemCollection class is responsible for loadingmetadata about the conceptual model. TheEdmItemCollection class loads its metadata from aconceptual schema definition language (CSDL) file that

is an XML representation of the conceptual model.


13/38

StoreItemCollection:

An StoreItemCollection class is responsible for loadingthe metadata about the storage (database) model. TheStoreItemCollection class loads its metadata from astore schema definition language (SSDL) file that is anXML representation of the storage model.

StorageMappingItemCollection :

A StorageMappingItemCollection class is responsiblefor loading metadata that represents the mappingbetween the conceptual model and the storage(database) model.

The StorageMappingItemCollection class loads itsmetadata from a mapping specification language (MSL)file that is an XML representation of the mapping betweenthe conceptual model and the storage model.


14/38

ADO.NET

ADO.NET is a set of classes that expose dataaccess services for .NET Framework programmers.

ADO.NET provides a rich set of components forcreating distributed, data-sharing applications.

It is an integral part of the .NET Framework,providing access to relational, XML, and applicationdata.

ADO.NET supports a variety of development needs,including the creation of front-end database clientsand middle-tier business objects used by

applications, tools, languages, or Internet browsers.


15/38

ADO.NET OVERVIEW ADO.NET provides consistent access to data sources such

as SQL Server and XML, and to data sources exposedthrough OLE DB and ODBC. Data-sharing consumerapplications can use ADO.NET to connect to these datasources and retrieve, handle, and update the data that theycontain.

ADO.NET separates data access from data manipulation intodiscrete components that can be used separately or intandem.

ADO.NET includes .NET Framework data providers forconnecting to a database, executing commands, andretrieving results. Those results are either processed directly,

placed in an ADO.NET Dataset object in order to be exposedto the user in an ad hoc manner, combined with data frommultiple sources, or passed between tiers.

The Dataset object can also be used independently of a .NETFramework data provider to manage data local to theapplication or sourced from XML.


16/38

ADO.NET ARCHITECTURE


17/38

Advantages of ADO. Net :

ADO. Net works on disconnected architecture.

data can be cached in datasets.

data is persisted as XML.

Performance : Extremely Fast.

Disadvantages of ADO. Net: Providing a comprehensive disconnected data-

access model, which is crucial to the Webenvironment

Providing tight integration with XML, and Providing seamless integration with the .NET

Framework (e.g., compatibility with the baseclass library's type system).


18/38

DAO & RDO in ADO

Data Access Objects (DAO) can be used either with theMicrosoft Jet database engine or, using the ODBCDirect option,without it.

This chapter discusses design and implementation issues thatarise when using the Data Access Objects (DAO) to access

remote databases. Remote Data Objects (RDO) implement a set of objects to deal

with the special requirements of remote data access.

RDO implements a thin code layer over the ODBC API anddriver manager that establishes connections, creates result setsand cursors, and executes complex procedures using minimal

workstation resources. Although RDO is also accessed by DAO when your code

creates an ODBCDirect Workspace object, documentation forthis implementation can be found by searching for specific

ODBCDirect topics.


19/38

Features of Remote Data Objects With RDO and the RemoteData control, your applications can access

ODBC data sources without using a local query processor

By using RDO, you can:

Create simple cursorless result sets, or more complex cursors.

Run queries and process any number of result sets.

Execute stored procedures that return result sets with or without outputparameters and return values.

Execute action queries that perform data manipulation or data definitionoperations.


20/38

Data Providers


21/38

.NET Framework data provider Description

.NET Framework Data Provider for

SQLServer

For Microsoft SQL Server version

7.0 or later.

.NET Framework Data Provider forOLE DB

For data sources exposed using OLEDB.


ODBC

For data sources exposed using ODBC.

Note The .NET Framework Data

Provider for ODBC is not included in the

.NET Framework version 1.0. If yourequire the .NET Framework Data

Provider for ODBC and are using the

.NET Framework version 1.0, you can

download the .NET Framework Data

Provider for ODBC at

http://msdn.microsoft.com/downloads.The namespace for the downloaded


ODBC is Microsoft.Data.Odbc.


22/38


Oracle

For Oracle data sources. The .NET

Framework Data Provider for Oracle

supports Oracle client software version

8.1.7 and later. Note The .NET

Framework Data Provider for Oracle is

not included in the .NET Frameworkversion 1.0. If you require the .NET

Framework Data Provider for Oracle

and are using the .NET Framework

version 1.0, you can download the .NET

Framework Data Provider for Oracle at

http://msdn.microsoft.com/downloads.


23/38

core elements of the .NET

Framework data provider model

Object Description

Connection Establishes a connection to a specific

data source.

Command Executes a command against a data

source.

DataReader Reads a forward-only, read-only

stream of data from a data source.

DataAdapter Populates a DataSet and resolves

updates with the data source.


24/38

Connection Class

SqlConnection con = new

SqlConnection(@"Data Source=JLC-

A10ADD7FFE4\SQLEXPRESS;Initial

Catalog=srinivas;IntegratedSecurity=True");

Here con is the connection class object

Using connection class con we areconnecting to database using

connection string


25/38

Connection Strings

A connection string contains initializationinformation that is passed as a parameter froma data provider to a data source.

The syntax depends on the data provider, and

the connection string is parsed during theattempt to open a connection.

Syntax errors generate a run-time exception,but other errors occur only after the datasource receives connection information.

Once validated, the data source applies theoptions specified in the connection string andopens the connection.


26/38

Command class Initialization of object:

SqlCommand cmd;

Methods of SqlCommand class:

ExecuteNonQuery()used for INSERT,UPDATE,DELETE

ExecuteScalar()

used to perform changes to single column

ExecuteReader()

used for select statement


27/38

Using Commands to Modify Data

(ADO.NET) Using a .NET Framework data provider, you can execute

stored procedures or data definition language statements(for example, CREATE TABLE and ALTER COLUMN) toperform schema manipulation on a database or catalog.These commands do not return rows as a query would, so

the Command object provides an ExecuteNonQuery toprocess them.

In addition to using ExecuteNonQuery to modify schema,you can also use this method to process SQL statementsthat modify data but that do not return rows, such asINSERT, UPDATE, and DELETE.

Although rows are not returned by the ExecuteNonQuerymethod, input and output parameters and return values canbe passed and returned via the Parameters collection ofthe Command object.


28/38

Data Reader and Data Adapters

You can use the ADO.NET DataReaderto retrieve a read-only, forward-only stream of data from a database. Resultsare returned as the query executes, and are stored in thenetwork buffer on the client until you request them usingthe Read method of the DataReader. Using theDataReadercan increase application performance both by

retrieving data as soon as it is available, and (by default)storing only one row at a time in memory, reducing systemoverhead.

A DataAdapteris used to retrieve data from a data sourceand populate tables within a DataSet. The DataAdapteralso resolves changes made to the DataSet back to the

data source. The DataAdapter uses the Connection objectof the .NET Framework data provider to connect to a datasource, and it uses Command objects to retrieve data fromand resolve changes to the data source.


29/38

Classes in .NET Data provider

Object Description

Transaction Enables you to enlist commands in

transactions at the data source.

CommandBuilder A helper object that will automatically

generate command properties of aDataAdapteror will derive parameter

information from a stored procedure

and populate the Parameters

collection of a Command object.

Parameter Defines input, output, and return value

parameters for commands and stored

procedures.


30/38

Exception Returned when an error is

encountered at the data source. For

an error encountered at the client,

.NET Framework data providers throw

a .NET Framework exception.

Error Exposes the information from a

warning or error returned by a data

source.

ClientPermission Provided for .NET Framework data

provider code access security

attributes.


31/38

Transaction handling

Begin Transaction

Some code to update records

Some code to select some records

Retrieve some data from the selected records

Update some value depending upon selected

records

Commit Transaction


32/38

App.config file Windows applications in VS.NET use the

name app.configby default for theconfiguration file.

This will not be automatically created when

you create a Windows application. If you needa configuration file for your application, openyour project in VS.NET, go to the 'SolutionExplorer' and right click on the project name.ChooseAdd>Addnewitem from the menu

and select 'Application Configuration file' fromthe list of choices. This will create anapp.config file for you in the application root.

By default, the app.config file will have thefollowing content:


33/38

Store values in config file

To store values in the configuration file,

you can create XML elements in the

format:


34/38

See the sample config entries below:


35/38

Read values from config file

To read from this config file, just use the

following code in your application:

string dbPath =

System.Configuration.ConfigurationSetti

ngs.AppSettings["DatabasePath"];

string email =

System.Configuration.ConfigurationSettings.AppSettings["SupportEmail"];


36/38

ConfigurationSettings is the class used toaccess the contents of the configuration

file using System.Configuration;

If you have the above directive on top offile, we can use

string dbPath =ConfigurationSettings.AppSettings["DatabasePath"];

string email =ConfigurationSettings.AppSettings["SupportEmail"];


37/38

In VB.NET, you have to use "( ... )"

instead of the "[ ... ]", as shown below:

Dim dbPath as String =

ConfigurationSettings.AppSettings("Data

basePath")

Dim email as String =ConfigurationSettings.AppSettings("Sup

portEmail")


38/38

Thank you.

reflection and ado

Documents