VISUAL PROGRAMMING

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VISUAL PROGRAMMING

• V.VSUBRAHMANYAM,
• LECTUER
• SOCIS, IGNOU

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Objectives

• Multiple Document Interface
• MDI form
• MDI Application
• Grid Control
• Common Dialog Control
• Additional Controls

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Contd

• VB database Architecture
• Visual Data Manager
• Data Control
• OLE DB
• ADO
• ADO Data Control
• Active X control

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Multiple Document Interface (MDI)

• Designed for document centered applications.
• It is used for opening many windows at the same
  time.
• All the document windows are contained in a
  parent window, which provides a workspace in the
  application.
• VB application can have only one MDI form, which
  contains all the child forms.

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Child form

• It is an ordinary form that has its child
  property set to True.
• Child form cannot be moved outside the Parents
  forms boundaries.
• When it is minimized, its icon appear at the
  bottom of the workspace of the parent form.
• There can be more than one child forms

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Why MDI forms?

• It acts like a container for the other forms in
  the application.
• Will allow easier organization of the forms in
  the application
• Reduce the amount of code.
• Reduce the number of controls.

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MDI application

• An MDI application consists of
• One MDI parent form
• One or more MDI child form(s)
• Optionally independent forms and modules

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Grid Control

• Grid control is an OCX control.
• This is used to create applications that present
  information in rows and columns.
• It displays information in cells.
• Grid control contains fixed and non-fixed rows
  and columns.

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Contd

• It supports properties such as ColWidth,
  RowHeight, SelEndCol, SelEndRow, SelstartRow and
  SelStartCol.
• A grahic object can be added to a cell in the
  Grid control.

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Common Dialog control

• To provide standardization in the interface for
  all Windows complaint applications.
• Allows to deploy the dialog boxes that it
  provides with all its applications.

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Common Dialog control

• It lets to display the following dialog boxes
• Open a file
• Save a file
• Set a color
• Set a font
• Print a Document

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Additional controls

• SSTab
• ImageList
• MSFlexGrid
• TabStrib
• ToolBar

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Contd

• StatusBar
• Tree View
• Slider Control
• Mask Edit Box

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VB Database Architecture

• VB database application has 3 parts
• User Interface
• Database Engine
• Data store

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• Database Engine lies between the program and
  physical database.
• User Interface is what the user sees and interact
  with.
• Data store is the file or files containing the
  database tables.

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User interface
Data base Engine
Data Store
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Accessing databases in VB

• VB provides a set of tools to create and use
  structured database systems to manage
  applications data.
• MS Jet Database engine
• Data control
• Data Access Objects(DAO)

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Jet Database Engine

• It is contained in a set of DLL files that are
  linked to the VB program at runtime.
• It translates the applications request into
  physical operations on Data store.
• It reads, writes and modifies the database and
  handles indexing, locking and referential
  integrity and also contains and query processor

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• Data Control and Data Access objects are the
  interfaces used to connect to the Jet Database
  engine.

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VB and databases

• VB recognizes 3 categories of databases
• VB Database
• External Databases
• ODBC Databases

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VB Database

• These databases are created and manipulated by
  the Jet engine and provide maximum flexibility
  and speed.
• These are also called Native databases and they
  use the same format as MS-Access.

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External Databases

• These are indexed sequential Access method
  databases in several formats including dBase III,
  dBase IV, MS-Foxpro, Paradox.
• Text file databases, Spreadsheets, HTML tables
  and lists can also be accessed.

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ODBC Databases

• These are Client-Server databases that confirm to
  the ODBC standard such as MS-SQL server, Oracle,
  DB2 etc.

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Visual Data Manager

• A database can be created with the help of Visual
  Data Manager (s/w utility) from Add-Ins menu of
  VB.

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Data control

• Establishes a connection to a database
• Returns a set of records from the database.
• Enables to move from record to record.
• Enables to display and manipulate data from the
  records in bound controls.

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Data control properties

• Two important properties are to be set for the
  data control at runtime or design time. They are
• Database Name
• Record Source

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Recordset

• VB connects to the database specified, and
  returns a set of records for the table(s) in the
  form of a Recordset.
• It is an object that points to the data in the
  database.
• It is the set of records returned, based on the
  Record Source property of the Datacontrol.

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Other forms of data

• There is need to access data from the other
  sources such as mail, Internet content, directory
  data from other machines and others.

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OLE DB

• The general solution Microsoft offers to the
  priorily mentioned problem is OLE DB, a set of
  COM interfaces that provide uniform access to
  data stored in diverse information sources.

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OLE DB

• It is a new low-level interface that is part of
  the Universal Data Access platform.
• It is defined as a general purpose set of
  interfaces designed to let developers build data
  access tools as components using the COM.

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Contd

• It enables applications to have uniform access to
  data stored in DBMS and non-DBMS information
  containers.
• OLE DB has providers which lets access the
  different data sources.

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OLE DB services

• A cursor service
• A service to perform batch updates
• A shape service to build the data in the form of
  a hierarchy.
• A remote data service provider for managing data
  in multi-tier environments over connected or
  disconnected networks.

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Disadvantage of OLE DB

• VB cannot access the OLE DB directly because of
  its sophistication.

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ActiveX Data Object (ADO)

• To solve the problem ADO comes into picture which
  acts like the intermediary between the
  application and the OLE DB.

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ADO

• It enables your client applications to access and
  manipulate data in a data base server through any
  of the OLE DB providers.

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Benefits of ADO

• Ease of use
• High speed
• Low Memory overheads
• Small disk foot print.
• It supports key features for building Client /
  Server and Web-based applications.

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ADO Data control

• We can display the data from a datasource using
  ADO code or with the help of ADO data control.
• In order to use the ADO data, we need to add the
  ADO data control to the form.

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Active X control

• Active X is OLE with some extensions for the
  Internet.
• These are created by using existing controls, or
  from scratch.
• This can be used by other development tools as
  well.
• Controls like MSFlexGrid, Sheridan controls are
  all Active X controls

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Active X and Internet

• Active X controls can be added to Web pages to
  improve the functionality of the Page.
• This can be loaded on the page to play a movie
  clip .avi file or to present a form.

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Active X Control pad

• Microsoft has provided a new tool to simplify the
  addition of Active X controls to a page and is
  called as Microsoft Active X Control Pad.