VB.NET DataView类代码示例

Private Sub DemonstrateDataView()
    ' Create one DataTable with one column.
    Dim table As New DataTable("table")
    Dim colItem As New DataColumn("item", _
        Type.GetType("System.String"))
    table.Columns.Add(colItem)

    ' Add five items.
    Dim NewRow As DataRow
    Dim i As Integer
    For i = 0 To 4
    
    NewRow = table.NewRow()
    NewRow("item") = "Item " & i
    table.Rows.Add(NewRow)
    Next
    table.AcceptChanges()

    ' Create two DataView objects with the same table.
    Dim firstView As New DataView(table)
    Dim secondView As New DataView(table)
    
    ' Change the values in the table.
    table.Rows(0)("item") = "cat"
    table.Rows(1)("item") = "dog"
    
    ' Print current table values.
    PrintTableOrView(table, "Current Values in Table")
        
    ' Set first DataView to show only modified versions of original rows.
    firstView.RowStateFilter = DataViewRowState.ModifiedOriginal

    ' Print values.    
    PrintTableOrView(firstView, "First DataView: ModifiedOriginal")

    ' Add one New row to the second view.
    Dim rowView As DataRowView
    rowView = secondView.AddNew()
    rowView("item") = "fish"
    ' Set second DataView to show modified versions of 
    ' current rows, or New rows.
    secondView.RowStateFilter = DataViewRowState.ModifiedCurrent _
        Or DataViewRowState.Added
    ' Print modified and Added rows.
    PrintTableOrView(secondView, _
        "Second DataView: ModifiedCurrent or Added")
End Sub
    
Overloads Private Sub PrintTableOrView( _
    ByVal view As DataView, ByVal label As String)
    Console.WriteLine(label)
    Dim i As Integer
    For i = 0 To view.count - 1
    
    Console.WriteLine(view(i)("item"))
    Next
    Console.WriteLine()
End Sub
    
Overloads Private Sub PrintTableOrView( _
    ByVal table As DataTable, ByVal label As String)
    Console.WriteLine(label)
    Dim i As Integer
    For i = 0 To table.Rows.Count - 1
    Console.WriteLine(table.Rows(i)("item"))
    Next
    Console.WriteLine()
End Sub

Dim orders As DataTable = dataSet.Tables("SalesOrderHeader")

Dim query = _
    From order In orders.AsEnumerable() _
    Where order.Field(Of Boolean)("OnlineOrderFlag") = True _
    Order By order.Field(Of Decimal)("TotalDue") _
    Select order

Dim view As DataView = query.AsDataView()
bindingSource1.DataSource = view

' 导入命名空间
Imports System
Imports System.Data
Imports System.Data.SqlClient


public class MainClass
   Shared Sub Main()
      Dim thisConnection As New SqlConnection("server=(local)\SQLEXPRESS;" & _
          "integrated security=sspi;database=MyDatabase")

      Dim sql As String = "SELECT FirstName, LastName FROM Employee"

      Try
         Dim da As New SqlDataAdapter
         da.SelectCommand = New SqlCommand(sql, thisConnection)

         Dim ds As New DataSet
         da.Fill(ds, "Employee")

         Dim dt As DataTable = ds.Tables("Employee")

         Dim dv As New DataView(dt, _
            "FirstName = 'Joe'", _
            "FirstName", DataViewRowState.CurrentRows)

         ' Display Data In Data View
         For Each row As DataRowView In dv
            For i As Integer = 0 To dv.Table.Columns.Count - 1
               Console.Write(row(i).PadRight(20))
            Next
            Console.WriteLine()
         Next

      Catch ex As SqlException
         ' Display error
         Console.WriteLine("Error: " & ex.ToString())
      Finally
         ' Close Connection
         thisConnection.Close()
         Console.WriteLine("Connection Closed")
      End Try
   End Sub
End Class