Chapter 7 - Programming in VB.NET

DB Visual ARCHITECT (DB-VA) can generate C#.NET source code so you can implement your application by C# programming language directly but you also can choose another language (VB.NET or C++) based on your taste in the .NET Framework. DB-VA generates DLL files and persistent libraries that can be referenced by .NET projects of language other than C#.

In this chapter:

• Introduction
• Generating DLL file
• Creating VB.NET Project
• Adding Referenced Project
• Working with the Generated Code and Persistent Library
• Running the Application

Introduction

Visual Basic .NET (VB.NET) is an Object-Oriented computer language that can be viewed as an evolution of Microsoft’s Visual Basic (VB) implemented on the Microsoft .NET framework. The .NET Framework contains a virtual machine called Common Intermediate Language (CIL). Simply put, programs are compiled to produce CIL and the CIL is distributed to user to run on a virtual machine. VB.NET, C++, C# compilers are available from Microsoft for creating CIL. In DB-VA you can generate C# persistent source code and DLL files, so you can reference the DLL file and Persistent Library in Visual Studio .NET 2003 and develop the VB.NET application.

In the following section, you will develop a VB.NET application. The application is exactly the same as the one in Chapter 4 – Developing Standalone .NET Application sample but this time you use VB.NET instead of C# for development. You need to download Chapter 4 sample application because it contains the DLL file and persistent libraries for your VB.NET project.

Generating DLL File

1. From the menu bar, select Tools > Object-Relational Mapping (ORM) > Generate Database… to open the Database Code Generation dialog box.

   

2. Check the Compile to DLL option to generate the DLL file.
   • Compile to DLL

     By checking this option, DB-VA will generate DLL files which can be referenced by .NET projects of language other than C#. DB-VA generates a batch file for this DLL file at the same time. You can modify the configure file (hibernate.cfg.xml) manually and use the batch file to recompile and build an up-to-date DLL file for referenced project.

     

Creating VB.NET Project

1. Open Microsoft Visual Studio .NET 2003.
2. Select File > New > Project … from the menu.

   

3. Select the Project Types as Visual Basic Projects and Templates as Windows Application and enter the Name and Location for the new application.

   

4. The School System Project is created.

   

Adding Referenced Project

1. Right click References under the Standalone School System VB.NET project and select Add Reference… to add the C# example DDL file and persistent libraries.

   

2. Click Browse… on the Add Reference dialog box to select the folder of the downloaded C# standalone application sample. Select C# sample folder/bin/SchoolSystem.dll and all libraries in C# sample folder/lib.

   

   

Working with the Generated Code and Persistent Library

• Importing DLL and Persistent Libraries namespace for the Class.

  VB.NET	C#
  Imports school Imports Orm	using school; using Orm;

• Creating PersistentTransaction when manipulating the database.

  VB.NET	C#
  Dim t As PersistentTransaction = SchoolSystemPersistentManager.Instance.GetSession.BeginTransaction	PersistentTransaction t = SchoolSystemPersistentManager.Instance().GetSession().BeginTransaction();

• Creating Object and Save to Database
  
  1. From menu bar, select File > Register Student to open the Add Student dialog box.

     

  2. Fill in the student information. Click OK to create the new Student record in School System.

     

  3. After click OK, the system create the new Student persistent object.

     Private Sub okButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles okButton.Click     If (loginIDTextBox.Text.Length = 0 Or passwordTextBox.Text.Length = 0) Then         MessageBox.Show("Login id or password missing")         Return     End If     Dim t As PersistentTransaction = SchoolSystemPersistentManager.Instance.GetSession.BeginTransaction     Try         If (_userType = CREATE_TEACHER) Then             User = TeacherFactory.CreateTeacher()         ElseIf (_userType = CREATE_STUDENT) Then             User = StudentFactory.CreateStudent()         End If

     Source File : Standalone School System VB.NET\RegisterDialog.vb

  4. Set the student information from the text fields value to the Student object.

     User.Password = passwordTextBox.Text User.LoginID = loginIDTextBox.Text If (TypeOf User Is Teacher) Then     CType(User, Teacher).Email = emailTextBox.Text End If

     Source File : Standalone School System VB.NET\RegisterDialog.vb

  5. Call Save() method of Student Persistent Object and Commit() method of PersistentTransaction., then the new Student object will be saved to the database. If any error occurred during the transaction, you can call the Rollback() method to cancel the proposed changes in a pending database transaction

     User.Save()     t.Commit()     DialogResult = DialogResult.OK     Close() Catch ex As Exception     Console.WriteLine(ex.InnerException.Message)     DialogResult = DialogResult.Cancel     t.RollBack() End Try

     Source File : Standalone School System VB.NET\RegisterDialog.vb

• Query Object from Database

  After the user login the School System, the system query different Course objects from the database according to user role. If the user is a student, the system shows all the courses. The student can select and register the course. If the user is a teacher, the system shows courses are created by that teacher. The teacher can update or delete the course in the system.

  Student Login:

  

  Teacher Login:

  

  
  
  1. Query the course objects when user login. When Student login, the system will call ListCourseByQuery() method in CourseFactory to get all available courses. When Teacher login, the system will call courses collection variable in Teacher object.

     Private Sub UpdateTreeView()     Dim lCourses() As Course     If (TypeOf CurrentUser Is Student) Then         lCourses = CourseFactory.ListCourseByQuery(Nothing, Nothing)     ElseIf (TypeOf CurrentUser Is Teacher) Then         lCourses = CType(CurrentUser, Teacher).courses.ToArray()     End If     ... End Sub

     Source File : Standalone School System VB.NET \SchoolSystemForm.vb

• Update Object and Save to Database

  You can modify the user information and update the record in database. After the user login, the User object is stored in the application, so you can set new information to the user object and update the database record.

  1. From the menu bar, select User > Modify User Information to open the Modify User Information dialog box.
     
  2. Enter new user information and click OK to update the User record.
     
  3. Update the information for the User object by setting password, name and email address.

     Private Sub okButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles okButton.Click     If (nameTextBox.Text.Length = 0 Or passwordTextBox.Text.Length = 0) Then         MessageBox.Show("Missing login id and password")     Else         Dim t As PersistentTransaction = SchoolSystemPersistentManager.Instance.GetSession.BeginTransaction         Try             _user.Name = nameTextBox.Text             _user.Password = passwordTextBox.Text             If (TypeOf _user Is Teacher) Then                 CType(_user, Teacher).Email = emailTextBox.Text             End If             _user.Save()             DialogResult = DialogResult.OK             t.Commit()         Catch ex As Exception             DialogResult = DialogResult.Cancel             t.RollBack()         End Try     End If     Close() End Sub

     Source File : Standalone School System VB.NET\ModifyUserDialog.cs

• Delete Object in Database

  Teacher can create course for students to register, and they can cancel courses in the system. They only need to click delete button of the course then the course information will be deleted in the database and all its relationships with registered students will be removed.

  1. Teacher can create the course by clicking the Add Course button, fill in Course name and Description.

     

  2. Student can register the course by clicking the Register button.

     

  3. The teacher can view how many students registered his course, and he can delete courses in the system.

     

  4. Click Delete of a course then it will trigger the delButton_Click() method .

     Private Sub deleteButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles deleteButton.Click     If (MessageBox.Show("Delete", "Delete", MessageBoxButtons.OKCancel).Equals(DialogResult.OK)) Then

     Source File : Standalone School System VB.NET\CoursePanel.vb

  5. Call deleteAndDissociate() method to delete the course object and remove the relationships of students and teachers with it.

     Dim t As PersistentTransaction = SchoolSystemPersistentManager.Instance().GetSession().BeginTransaction()         Try             _CourseNode.Course().DeleteAndDissociate()             _CourseNode.Remove()             t.Commit()         Catch ex As Exception             Console.WriteLine(ex.InnerException.Message)             t.RollBack()         End Try     End If End Sub

     Source File : Standalone School System VB.NET\CoursePanel.vb

Running Application

The VB.NET project is implemented in Visual Studio .NET 2003. To execute the VB.NET Application, select Debug > Start (F5) from the menu bar.

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