Visual Basic .NET - ADO .Net - DataAdapter Class

The DataAdapter class in VB.NET is a bridge between a DataSet and a data source, typically a database. It facilitates the retrieval and manipulation of data from the data source and synchronizes the changes made in the DataSet back to the data source.

Connection: To work with a DataAdapter, you need to provide it with a connection to the data source. This is typically done by setting the Connection property of the DataAdapter to an instance of the appropriate connection class, such as the SqlConnection.

SQL Commands: The DataAdapter relies on SQL commands to interact with the data source. It typically uses four types of commands: SelectCommand for retrieving data, InsertCommand for inserting new data, UpdateCommand for updating existing data, and DeleteCommand for deleting data. You can set these commands on the DataAdapter using their respective properties.

Filling a DataSet: The Fill method of the DataAdapter is used to populate a DataSet with data from the data source. You pass the DataSet as a parameter to the Fill method, along with the name of the DataTable to be filled and the SQL command or stored procedure to retrieve the data.

Updating a Data Source: The Update method of the DataAdapter is used to update the data source with the changes made in the DataSet. It takes the DataSet as a parameter and applies the appropriate Insert, Update, and Delete commands to reflect the changes in the data source.

CommandBuilder: The CommandBuilder class is used to automatically generate the InsertCommand, UpdateCommand, and DeleteCommand of the DataAdapter based on the SelectCommand. It saves you from explicitly creating and setting these commands.

Batch Updates: The DataAdapter supports batch updates, which means it can send multiple changes to the data source in a single round trip. This improves performance when updating a large number of records.

Handling Concurrency: The DataAdapter provides options for handling concurrency issues, such as when multiple users are updating the same data simultaneously. You can specify how conflicts should be resolved, whether by overwriting changes or raising an exception.

Here's an example that demonstrates the usage of the DataAdapter class:

Imports System.Data.SqlClient
Module Program
    Sub Main()
        ' Connection string
        Dim connectionString As String = "Data Source=ServerName;Initial Catalog=DatabaseName;User ID=Username;Password=Password"
        ' SQL command
        Dim commandText As String = "SELECT * FROM Customers"
        ' Create a new SqlConnection object
        Dim connection As New SqlConnection(connectionString)
        ' Create a new DataAdapter
        Dim adapter As New SqlDataAdapter(commandText, connection)
        ' Create a new DataSet
        Dim dataSet As New DataSet()
        Try
            ' Fill the DataSet with data from the database
            adapter.Fill(dataSet, "Customers")
            ' Modify the data in the DataSet
            Dim dataTable As DataTable = dataSet.Tables("Customers")
            For Each row As DataRow In dataTable.Rows
                row("Email") = "[email protected]"
            Next
            ' Update the data source with the changes
            adapter.Update(dataSet, "Customers")
            Console.WriteLine("Data updated successfully.")
        Catch ex As Exception
            ' Handle any exceptions
            Console.WriteLine("Error: " & ex.Message)
        Finally
            ' Ensure the connection is always closed
            If connection.State = ConnectionState.Open Then
                connection.Close()
            End If
        End Try
    End Sub
End Module

In the example, replace "ServerName", "DatabaseName", "Username", and "Password" with the appropriate values for your SQL Server database. The SqlDataAdapter is created with the SQL command and the SqlConnection. The Fill method is used to populate the