MoveFirst、MoveLast、MoveNext 和 MovePrevious 方法示例 (VB)

此示例使用 MoveFirst、MoveLast、MoveNext 和 MovePrevious 方法根据提供的命令移动记录集的记录指针。 若要运行此过程，需要 MoveAny 过程。

'BeginMoveFirstVB  
  
    'To integrate this code  
    'replace the data source and initial catalog values  
    'in the connection string  
  
Public Sub Main()  
    On Error GoTo ErrorHandler  
  
    ' connection and recordset variables  
    Dim rstAuthors As ADODB.Recordset  
    Dim Cnxn As ADODB.Connection  
    Dim strCnxn As String  
    Dim strSQLAuthors  
     ' record variables  
    Dim strMessage As String  
    Dim intCommand As Integer  
  
    ' Open connection  
    Set Cnxn = New ADODB.Connection  
    strCnxn = "Provider='sqloledb';Data Source='MySqlServer';" & _  
        "Initial Catalog='Pubs';Integrated Security='SSPI';"  
    Cnxn.Open strCnxn  
  
    ' Open recordset from Authors table  
    Set rstAuthors = New ADODB.Recordset  
    rstAuthors.CursorLocation = adUseClient  
    ' Use client cursor to enable AbsolutePosition property  
    strSQLAuthors = "Authors"  
    rstAuthors.Open strSQLAuthors, Cnxn, adOpenStatic, adLockReadOnly, adCmdTable  
  
    ' Show current record information and get user's method choice  
    Do  
        strMessage = "Name: " & rstAuthors!au_fname & " " & _  
            rstAuthors!au_lname & vbCr & "Record " & _  
            rstAuthors.AbsolutePosition & " of " & _  
            rstAuthors.RecordCount & vbCr & vbCr & _  
            "[1 - MoveFirst, 2 - MoveLast, " & vbCr & _  
            "3 - MoveNext, 4 - MovePrevious]"  
        intCommand = Val(Left(InputBox(strMessage), 1))  
  
         ' for exiting the loop  
        If intCommand < 1 Or intCommand > 4 Then  
            MsgBox "You either entered a non-number or canceled the input box. Exit the application."  
            Exit Do  
        End If  
  
        ' Use specified method while trapping for BOF and EOF  
        Select Case intCommand  
            Case 1  
                rstAuthors.MoveFirst  
            Case 2  
                rstAuthors.MoveLast  
            Case 3  
                rstAuthors.MoveNext  
                If rstAuthors.EOF Then  
                    MsgBox "Already at end of recordset!"  
                    rstAuthors.MoveLast  
                End If  
            Case 4  
                rstAuthors.MovePrevious  
                If rstAuthors.BOF Then  
                    MsgBox "Already at beginning of recordset!"  
                    rstAuthors.MoveFirst  
                End If  
        End Select  
    Loop  
  
    ' clean up  
    rstAuthors.Close  
    Cnxn.Close  
    Set rstAuthors = Nothing  
    Set Cnxn = Nothing  
    Exit Sub  
  
ErrorHandler:  
    ' clean up  
    If Not rstAuthors Is Nothing Then  
        If rstAuthors.State = adStateOpen Then rstAuthors.Close  
    End If  
    Set rstAuthors = Nothing  
  
    If Not Cnxn Is Nothing Then  
        If Cnxn.State = adStateOpen Then Cnxn.Close  
    End If  
    Set Cnxn = Nothing  
  
    If Err <> 0 Then  
        MsgBox Err.Source & "-->" & Err.Description, , "Error"  
    End If  
End Sub  
  
'EndMoveFirstVB  

另请参阅

MoveFirst、MoveLast、MoveNext 和 MovePrevious 方法 (ADO)
记录集对象 (ADO)