Visual Basic Code Examples For Access

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1. Visual Basic Code Examples For Access Point
2. Sample Visual Basic Program Code

In this introduction to Microsoft Access Visual Basic for Applications programming, you will learn how to write your first code in Access VBA. Visual Basic 6.0 Examples. Web API Categories ASN.1 Amazon EC2 Amazon Glacier Amazon S3 Amazon S3 (new) Amazon SES Amazon SNS Amazon SQS Async Azure Cloud Storage Azure Service Bus Azure Table Service Base64 Bounced Email Box CAdES CSR CSV Certificates Compression DKIM / DomainKey DSA Diffie-Hellman Digital Signatures Dropbox. Apr 21, 2017 - Microsoft Access business database design and consulting. Web based programmers offering expert quoted solutions for database creation to match your requirements.

Before we write the code that connects our visual basic program to ms access, we will first add the Microsoft ADO 2.8 library in our visual basic. To add the Microsoft ADO 2.8 library, in the menu bar select Project and select References. In this example, let us access data in a DataGridView control using code. Take the following steps − Add a DataGridView control and a button in the form. Change the text of the button control to 'Fill'. Double click the button control to add the required code for the Click event of the button, as shown below −.

In visual basic, Access Modifiers are the keywords and those are useful to define an accessibility level for all the types and type members.

By specifying the access level for all the types and type members, we can control whether they can be accessed in other classes or in current assembly or in other assemblies based on our requirements.

The following are the different types of access modifiers available in a visual basic programming language.

• Friend (internal in c#)

By using these four access modifiers, we can specify a following six levels of accessibility for all types and type members based on our requirements.

Generally, in visual basic only one access modifier is allowed to use with any member or type, except when we use Protected Friend combination.

In visual basic, we are not allowed to use any access modifiers on namespaces, because the namespaces have no access restrictions.

Only certain access modifiers are allowed to specify based on the context in which the member declaration occurs. In case, if we didn’t mention any access modifiers during the member declaration, then the default access modifiers will be used depending on the member declaration context.

For example, the top-level types which are not nested in any other types can only have Public or Friend accessibility. The default accessibility for top-level types is Friend.

Visual Basic Public Access Modifier

In visual basic, Public modifier is useful to specify that access is not restricted, so the defined type or member can be accessed by any other code in the current assembly or another assembly that references it.

Following is the example of defining members with Public modifier in a visual basic programming language.

Module Module1

ClassUser

Public Name AsString

Public Location AsString

Public Age AsInteger

PublicSub GetUserDetails()

Console.WriteLine('Name: {0}', Name)

Console.WriteLine('Location: {0}', Location)

Console.WriteLine('Age: {0}', Age)

EndSub

EndClass

Sub Main()

Dim u AsUser = NewUser()

u.Name = 'Suresh Dasari'

u.Location = 'Hyderabad'

u.Age = 32

u.GetUserDetails()

Console.WriteLine(vbLf & 'Press Enter Key to Exit.')

Console.ReadLine()

EndSub

EndModule

If you observe the above example, we defined a Userclass with required variables and method using Public access modifier and trying to access those variables and method in another class with an object reference of Userclass.

When we execute the above visual basic program, we will get the result as shown below.

If you observe the above result, we are able to access the variables and methods of Userclass in another class because of specifying with Public specifier based on our requirements.

As discussed, the Public access specifier will make all the defined members or types available to all the types in our application.

Visual Basic Private Access Modifier

In visual basic, Private modifier is useful to specify that access is limited to the containing type so the defined type or member can only be accessed by the code in the same class or structure.

Following is the example of defining members with Private modifier in a visual basic programming language.

Module Module1

ClassUser

Private Name AsString

Private Location AsString

Private Age AsInteger

PrivateSub GetUserDetails()

Console.WriteLine('Name: {0}', Name)

Console.WriteLine('Location: {0}', Location)

Console.WriteLine('Age: {0}', Age)

EndSub

EndClass

Sub Main()

Dim u AsUser = NewUser()

' Complie-time Error

' These are inaccessible due to private specifier

u.Name = 'Suresh Dasari'

u.Location = 'Hyderabad'

u.Age = 32

u.GetUserDetails()

Console.WriteLine(vbLf & 'Press Enter Key to Exit.')

Console.ReadLine()

EndSub

EndModule

If you observe the above example, we defined a Userclass with required variables and method using Private access modifier and trying to access those variables and method in another class with an object reference of Userclass.

When we execute the above visual basic program, we will get compile-time errors like as shown below.

If you observe the above result, we got the compile-time error because the Private modifier members of Userclass referred in another class.

As discussed, the Private modifier type or member can be accessed only by the code within the same class or structure.

Visual Basic Protected Access Modifier

In visual basic, Protected modifier is useful to specify that access is limited to the containing type or types derived from the containing class so the type or member can only be accessed by code within the same class or in a derived class.

Following is the example of defining members with Protected modifier in a visual basic programming language.

Module Module1

ClassUser

Protected Name AsString

Protected Location AsString

Protected Age AsInteger

ProtectedSub GetUserDetails()

Console.WriteLine('Name: {0}', Name)

Console.WriteLine('Location: {0}', Location)

Console.WriteLine('Age: {0}', Age)

EndSub

EndClass

Sub Main()

Dim u AsUser = NewUser()

' Complie-time Error

' These are inaccessible due to protected specifier

u.Name = 'Suresh Dasari'

u.Location = 'Hyderabad'

u.Age = 32

u.GetUserDetails()

Console.WriteLine(vbLf & 'Press Enter Key to Exit.')

Console.ReadLine()

EndSub

EndModule

If you observe the above example, we defined a Userclass with required variables and method using Protected access modifier and trying to access those variables and method in another class with an object reference of Userclass.

When we execute the above visual basic program, we will get compile-time errors like as shown below.

If you observe the above result, we got a compile-time error because the Protected modifier members of Userclass referred in another class.

As discussed, the Protected members of a base class can be accessible in a derived class, only when access occurs through the derived class type.

Following is the example of accessing a base classProtected members in derived class through derived class type.

Class User

Protected Name AsString

Protected Location AsString

Protected Age AsInteger

ProtectedSub GetUserDetails()

Console.WriteLine('Name: {0}', Name) Tx studio viewer.

Console.WriteLine('Location: {0}', Location)

Console.WriteLine('Age: {0}', Age)

EndSub

EndClass

Class Details

InheritsUser

PublicSharedSub Main()

Dim u AsUser = NewUser()

Dim d AsDetails = NewDetails()

' Complier Error

' protected members can only accessible with derived classes

' u.Name = 'Suresh Dasari';

d.Name = 'Suresh Dasari'

Visual Basic Code Examples For Access Point

d.Location = 'Hyderabad'

d.Age = 32

d.GetUserDetails()

Console.WriteLine(vbLf & 'Press Enter Key to Exit.')

Console.ReadLine()

Rcon tool. EndSub

EndClass

If you observe the above example, we are accessing base class (User) Protected members using the reference of derived class (Details) and if we uncomment the commented code we will get a compile-time error because we are trying to access the protected members with base class (User) reference instead of derived class (Details).

When we execute the above visual basic program, we will get the result as shown below.

This is how we can use Protected modifier in our visual basic applications to limit access of type or member in the same class or derived class based on our requirements.

Visual Basic Friend Access Modifier

In visual basic, Friend modifier is useful to specify that access is limited to the current assembly so the type or member can be accessed by any code in the same assembly, but not from another assembly.

Following is the example of defining members with Friend modifier in a visual basic programming language.

Module Module1

ClassUser

Friend Name AsString

Friend Location AsString

Friend Age AsInteger

FriendSub GetUserDetails()

Console.WriteLine('Name: {0}', Name)

Console.WriteLine('Location: {0}', Location)

Console.WriteLine('Age: {0}', Age)

EndSub

EndClass

Sub Main()

Dim u AsUser = NewUser()

u.Name = 'Suresh Dasari'

u.Name = 'Suresh Dasari'

u.Location = 'Hyderabad'

u.Age = 32

u.GetUserDetails()

Console.WriteLine(vbLf & 'Press Enter Key to Exit.')

Console.ReadLine()

EndSub

EndModule

If you observe the above example, we defined a Userclass with required variables and method using Friend access modifier and trying to access those variables and method in another class with an object reference of Userclass.

When we execute the above visual basic program, we will get the result as shown below.

If you observe the above result, we are able to access the variables and methods of Userclass in another class because of specifying with Friend specifier based on our requirements.

As discussed, in visual basic the Friend type or members are accessible within the files of the same assembly.

Visual Basic Protected Friend Access Modifier

In visual basic, the Protected Friend modifier is useful to specify that access is limited to the current assembly or types derived from the containing class. So, the type or member can be accessed by any code in the same assembly or by any derived class in another assembly.

Following is the example of defining members with Protected Friend modifier in a visual basic programming language.

Module Module1

ClassUser

ProtectedFriend Name AsString

ProtectedFriend Location AsString

ProtectedFriend Age AsInteger

ProtectedFriendSub GetUserDetails()

Console.WriteLine('Name: {0}', Name)

Console.WriteLine('Location: {0}', Location)

Console.WriteLine('Age: {0}', Age)

EndSub

EndClass

Sub Main()

Dim u AsUser = NewUser()

u.Name = 'Suresh Dasari'

u.Name = 'Suresh Dasari'

u.Location = 'Hyderabad'

u.Age = 32

u.GetUserDetails()

Console.WriteLine('Press Enter Key to Exit.')

Console.ReadLine()

EndSub

EndModule

If you observe the above example, we defined a Userclass with required variables and method using Protected Friend access modifier and trying to access those variables and method in another class with an object reference of Userclass.

When we execute the above visual basic program, we will get the result as shown below.

If you observe the above result, we are able to access the variables and methods of Userclass in another class because of specifying with Friend specifier based on our requirements.

As discussed, in visual basic the Protected Friend type or members are accessible from the current assembly or from the types that are derived from the containing class in another assembly.

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• Selected Reading

Applications communicate with a database, firstly, to retrieve the data stored there and present it in a user-friendly way, and secondly, to update the database by inserting, modifying and deleting data.

Sample Visual Basic Program Code

Microsoft ActiveX Data Objects.Net (ADO.Net) is a model, a part of the .Net framework that is used by the .Net applications for retrieving, accessing and updating data.

ADO.Net Object Model

ADO.Net object model is nothing but the structured process flow through various components. The object model can be pictorially described as −

The data residing in a data store or database is retrieved through the data provider. Various components of the data provider retrieve data for the application and update data.

An application accesses data either through a dataset or a data reader.

• Datasets store data in a disconnected cache and the application retrieves data from it.

• Data readers provide data to the application in a read-only and forward-only mode.

Data Provider

A data provider is used for connecting to a database, executing commands and retrieving data, storing it in a dataset, reading the retrieved data and updating the database.

The data provider in ADO.Net consists of the following four objects −

There are following different types of data providers included in ADO.Net

• The .Net Framework data provider for SQL Server - provides access to Microsoft SQL Server.

• The .Net Framework data provider for OLE DB - provides access to data sources exposed by using OLE DB.

• The .Net Framework data provider for ODBC - provides access to data sources exposed by ODBC.

• The .Net Framework data provider for Oracle - provides access to Oracle data source.

• The EntityClient provider - enables accessing data through Entity Data Model (EDM) applications.

DataSet

DataSet is an in-memory representation of data. It is a disconnected, cached set of records that are retrieved from a database. When a connection is established with the database, the data adapter creates a dataset and stores data in it. After the data is retrieved and stored in a dataset, the connection with the database is closed. This is called the 'disconnected architecture'. The dataset works as a virtual database containing tables, rows, and columns.

The following diagram shows the dataset object model −

The DataSet class is present in the System.Data namespace. The following table describes all the components of DataSet −

Connecting to a Database

The .Net Framework provides two types of Connection classes −

• SqlConnection − designed for connecting to Microsoft SQL Server.

• OleDbConnection − designed for connecting to a wide range of databases, like Microsoft Access and Oracle.

Example 1

We have a table stored in Microsoft SQL Server, named Customers, in a database named testDB. Please consult 'SQL Server' tutorial for creating databases and database tables in SQL Server.

Let us connect to this database. Take the following steps −

• Select TOOLS → Connect to Database

• Select a server name and the database name in the Add Connection dialog box.

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• Click on the Test Connection button to check if the connection succeeded.

• Add a DataGridView on the form.

• Click on the Choose Data Source combo box.

• Click on the Add Project Data Source link.

• This opens the Data Source Configuration Wizard.

• Select Database as the data source type

• Choose DataSet as the database model.

• Choose the connection already set up.

• Save the connection string.

• Choose the database object, Customers table in our example, and click the Finish button.

• Select the Preview Data link to see the data in the Results grid −

When the application is run using Start button available at the Microsoft Visual Studio tool bar, it will show the following window −

Example 2

In this example, let us access data in a DataGridView control using code. Take the following steps −

• Add a DataGridView control and a button in the form.

• Change the text of the button control to 'Fill'.

• Double click the button control to add the required code for the Click event of the button, as shown below −

• When the above code is executed and run using Start button available at the Microsoft Visual Studio tool bar, it will show the following window −

• Clicking the Fill button displays the table on the data grid view control −

Creating Table, Columns and Rows

We have discussed that the DataSet components like DataTable, DataColumn and DataRow allow us to create tables, columns and rows, respectively.

The following example demonstrates the concept −

Example 3

So far, we have used tables and databases already existing in our computer. In this example, we will create a table, add columns, rows and data into it and display the table using a DataGridView object.

Take the following steps −

• Add a DataGridView control and a button in the form.

• Change the text of the button control to 'Fill'.

• Add the following code in the code editor.

• When the above code is executed and run using Start button available at the Microsoft Visual Studio tool bar, it will show the following window −

• Clicking the Fill button displays the table on the data grid view control −