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TitleDisplay parent and child records in two DataGrid controls in VB .NET
DescriptionThis example shows how to display master and child records in two DataGrid controls in VB .NET.
KeywordsDataGrid, DataTable, bind, ADO.NET, data, database, relationship, parent/child, master/detail
CategoriesDatabase, Controls
When the program starts, it creates OleDbDataAdapters to select data from the Addresses and TestScores tables. It creates a DataSet and uses the adapters' Fill methods to load the data.

The program then creates a DataRelation object relating the two tables' ContactID fields. That defines a master/detail relationship between the two tables.

The program then binds the DataSet's Addresses table to the dgAddresses DataGrid. That makes this control display the parent records from the Addresses table.

Next the program binds the dgTestScores DataGrid to the DataSet's Addresses table's TestScores field. That makes the control display the child records. When the user clicks on the parent DataGrid to select a record in the Addresses table, this binding makes the child DataGrid display the corresponding records.

Private m_da_Addresses As OleDbDataAdapter
Private m_da_TestScores As OleDbDataAdapter
Private m_DataSet As DataSet

Private Sub Form1_Load(ByVal sender As System.Object, ByVal _
    e As System.EventArgs) Handles MyBase.Load
    Const SELECT_ADDRESSES As String = "SELECT * FROM " & _
    Const SELECT_TEST_SCORES As String = "SELECT * FROM " & _

    ' Get the database file name.
    Dim db_name As String = Application.StartupPath
    db_name = db_name.Substring(0, db_name.LastIndexOf("\"))
    db_name &= "\Contacts.mdb"

    ' Compose the connection string.
    Dim connect_string As String = _
          "Provider=Microsoft.Jet.OLEDB.4.0;" & _
          "Data Source=" & db_name & ";" & _
          "Persist Security Info=False"

    ' Create a DataAdapter to load the Addresses table.
    m_da_Addresses = New OleDbDataAdapter(SELECT_ADDRESSES, _

    ' Create a DataAdapter to load the Addresses table.
    m_da_TestScores = New _
        OleDbDataAdapter(SELECT_TEST_SCORES, connect_string)

    ' Create and fill the DataSet.
    m_DataSet = New DataSet
    m_da_Addresses.Fill(m_DataSet, "Addresses")
    m_da_TestScores.Fill(m_DataSet, "TestScores")

    ' Define the relationship between the tables.
    Dim data_relation As New _
        DataRelation("Addresses_TestScores", _
        m_DataSet.Tables("Addresses").Columns("ContactID"), _

    ' Bind the DataGrids to the DataSet's tables.
    dgAddresses.SetDataBinding(m_DataSet, "Addresses")
    dgTestScores.SetDataBinding(m_DataSet, _
End Sub
When the program is ending, it makes an OleDbCommandBuilder object for the adapter. The adapter will use the command builder to make SQL insert, update, and delete commands as necessary to update the data. It then calls the adapter's Update method to save the changes to the data.
' Save changes to the data.
Private Sub Form1_Closing(ByVal sender As Object, ByVal e _
    As System.ComponentModel.CancelEventArgs) Handles _
    ' Use a CommandBuilder to make the INSERT,
    ' UPDATE, and DELETE commands as needed.
    Dim cb_addresses As New _
    Dim cb_testscores As New _

    ' Update the database.
        m_da_Addresses.Update(m_DataSet, "Addresses")
        m_da_TestScores.Update(m_DataSet, "TestScores")
    Catch ex As Exception
    End Try
End Sub
For information on database programming in VB .NET, see my book Visual Basic .NET Database Programming.
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