vb System.Data.DataTable类(方法)实例源码

' Put the next line into the Declarations section.
private dataSet As DataSet 
 
Private Sub MakeDataTables()
    ' Run all of the functions. 
    MakeParentTable()
    MakeChildTable()
    MakeDataRelation()
    BindToDataGrid()
End Sub
 
Private Sub MakeParentTable()
    ' Create a new DataTable.
    Dim table As New DataTable("ParentTable")

    ' Declare variables for DataColumn and DataRow objects.
    Dim column As DataColumn 
    Dim row As DataRow 
 
    ' Create new DataColumn, set DataType, ColumnName 
    ' and add to DataTable.    
    column = New DataColumn()
    column.DataType = System.Type.GetType("System.Int32")
    column.ColumnName = "id"
    column.ReadOnly = True
    column.Unique = True

    ' Add the Column to the DataColumnCollection.
    table.Columns.Add(column)
 
    ' Create second column.
    column = New DataColumn()
    column.DataType = System.Type.GetType("System.String")
    column.ColumnName = "ParentItem"
    column.AutoIncrement = False
    column.Caption = "ParentItem"
    column.ReadOnly = False
    column.Unique = False

    ' Add the column to the table.
    table.Columns.Add(column)
 
    ' Make the ID column the primary key column.
    Dim PrimaryKeyColumns(0) As DataColumn
    PrimaryKeyColumns(0)= table.Columns("id")
    table.PrimaryKey = PrimaryKeyColumns
 
    ' Instantiate the DataSet variable.
    dataSet = New DataSet()

    ' Add the new DataTable to the DataSet.
    dataSet.Tables.Add(table)
 
    ' Create three new DataRow objects and add 
    ' them to the DataTable
    Dim i As Integer
    For i = 0 to 2
       row = table.NewRow()
       row("id") = i
       row("ParentItem") = "ParentItem " + i.ToString()
       table.Rows.Add(row)
    Next i
End Sub
 
Private Sub MakeChildTable()
    ' Create a new DataTable.
    Dim table As New DataTable("childTable")
    Dim column As DataColumn 
    Dim row As DataRow 
 
    ' Create first column and add to the DataTable.
    column = New DataColumn()
    column.DataType= System.Type.GetType("System.Int32")
    column.ColumnName = "ChildID"
    column.AutoIncrement = True
    column.Caption = "ID"
    column.ReadOnly = True
    column.Unique = True

    ' Add the column to the DataColumnCollection.
    table.Columns.Add(column)
 
    ' Create second column.
    column = New DataColumn()
    column.DataType= System.Type.GetType("System.String")
    column.ColumnName = "ChildItem"
    column.AutoIncrement = False
    column.Caption = "ChildItem"
    column.ReadOnly = False
    column.Unique = False
    table.Columns.Add(column)
 
    ' Create third column.
    column = New DataColumn()
    column.DataType= System.Type.GetType("System.Int32")
    column.ColumnName = "ParentID"
    column.AutoIncrement = False
    column.Caption = "ParentID"
    column.ReadOnly = False
    column.Unique = False
    table.Columns.Add(column)
 
    dataSet.Tables.Add(table)

    ' Create three sets of DataRow objects, five rows each, 
    ' and add to DataTable.
    Dim i As Integer
    For i = 0 to 4
       row = table.NewRow()
       row("childID") = i
       row("ChildItem") = "Item " + i.ToString()
       row("ParentID") = 0 
       table.Rows.Add(row)
    Next i
    For i = 0 to 4
       row = table.NewRow()
       row("childID") = i + 5
       row("ChildItem") = "Item " + i.ToString()
       row("ParentID") = 1 
       table.Rows.Add(row)
    Next i
    For i = 0 to 4
       row = table.NewRow()
       row("childID") = i + 10
       row("ChildItem") = "Item " + i.ToString()
       row("ParentID") = 2 
       table.Rows.Add(row)
    Next i
End Sub
 
Private Sub MakeDataRelation()
    ' DataRelation requires two DataColumn 
    ' (parent and child) and a name.
    Dim parentColumn As DataColumn = _
        dataSet.Tables("ParentTable").Columns("id")
    Dim childColumn As DataColumn = _
        dataSet.Tables("ChildTable").Columns("ParentID")
    Dim relation As DataRelation = new _
        DataRelation("parent2Child", parentColumn, childColumn)
    dataSet.Tables("ChildTable").ParentRelations.Add(relation)
End Sub
 
Private Sub BindToDataGrid()
    ' Instruct the DataGrid to bind to the DataSet, with the 
    ' ParentTable as the topmost DataTable.
    DataGrid1.SetDataBinding(dataSet,"ParentTable")
End Sub

' 导入命名空间
Imports System.Data

Class Program
   Public Shared Sub Main(args As String())
      ' Create two tables and add them into the DataSet
      Dim orderTable As DataTable = CreateOrderTable()
      Dim orderDetailTable As DataTable = CreateOrderDetailTable()
      Dim salesSet As New DataSet()
      salesSet.Tables.Add(orderTable)
      salesSet.Tables.Add(orderDetailTable)

      ' Set the relations between the tables and create the related constraint.
      salesSet.Relations.Add("OrderOrderDetail", orderTable.Columns("OrderId"), orderDetailTable.Columns("OrderId"), True)

      Console.WriteLine("After creating the foreign key constriant, you will see the following error if inserting order detail with the wrong OrderId: ")
      Try
         Dim errorRow As DataRow = orderDetailTable.NewRow()
         errorRow(0) = 1
         errorRow(1) = "O0007"
         orderDetailTable.Rows.Add(errorRow)
      Catch e As Exception
         Console.WriteLine(e.Message)
      End Try
      Console.WriteLine()

      ' Insert the rows into the table
      InsertOrders(orderTable)
      InsertOrderDetails(orderDetailTable)

      Console.WriteLine("The initial Order table.")
      ShowTable(orderTable)

      Console.WriteLine("The OrderDetail table.")
      ShowTable(orderDetailTable)

      ' Use the Aggregate-Sum on the child table column to get the result.
      Dim colSub As New DataColumn("SubTotal", GetType([Decimal]), "Sum(Child.LineTotal)")
      orderTable.Columns.Add(colSub)

      ' Compute the tax by referencing the SubTotal expression column.
      Dim colTax As New DataColumn("Tax", GetType([Decimal]), "SubTotal*0.1")
      orderTable.Columns.Add(colTax)

      ' If the OrderId is 'Total', compute the due on all orders; or compute the due on this order.
      Dim colTotal As New DataColumn("TotalDue", GetType([Decimal]), "IIF(OrderId='Total',Sum(SubTotal)+Sum(Tax),SubTotal+Tax)")
      orderTable.Columns.Add(colTotal)

      Dim row As DataRow = orderTable.NewRow()
      row("OrderId") = "Total"
      orderTable.Rows.Add(row)

      Console.WriteLine("The Order table with the expression columns.")
      ShowTable(orderTable)

      Console.WriteLine("Press any key to exit.....")
      Console.ReadKey()
   End Sub

   Private Shared Function CreateOrderTable() As DataTable
      Dim orderTable As New DataTable("Order")

      ' Define one column.
      Dim colId As New DataColumn("OrderId", GetType([String]))
      orderTable.Columns.Add(colId)

      Dim colDate As New DataColumn("OrderDate", GetType(DateTime))
      orderTable.Columns.Add(colDate)

      ' Set the OrderId column as the primary key.
      orderTable.PrimaryKey = New DataColumn() {colId}

      Return orderTable
   End Function

   Private Shared Function CreateOrderDetailTable() As DataTable
      Dim orderDetailTable As New DataTable("OrderDetail")

      ' Define all the columns once.
      Dim cols As DataColumn() = {New DataColumn("OrderDetailId", GetType(Int32)), New DataColumn("OrderId", GetType([String])), New DataColumn("Product", GetType([String])), New DataColumn("UnitPrice", GetType([Decimal])), New DataColumn("OrderQty", GetType(Int32)), New DataColumn("LineTotal", GetType([Decimal]), "UnitPrice*OrderQty")}

      orderDetailTable.Columns.AddRange(cols)
      orderDetailTable.PrimaryKey = New DataColumn() {orderDetailTable.Columns("OrderDetailId")}
      Return orderDetailTable
   End Function

   Private Shared Sub InsertOrders(orderTable As DataTable)
      ' Add one row once.
      Dim row1 As DataRow = orderTable.NewRow()
      row1("OrderId") = "O0001"
      row1("OrderDate") = New DateTime(2013, 3, 1)
      orderTable.Rows.Add(row1)

      Dim row2 As DataRow = orderTable.NewRow()
      row2("OrderId") = "O0002"
      row2("OrderDate") = New DateTime(2013, 3, 12)
      orderTable.Rows.Add(row2)

      Dim row3 As DataRow = orderTable.NewRow()
      row3("OrderId") = "O0003"
      row3("OrderDate") = New DateTime(2013, 3, 20)
      orderTable.Rows.Add(row3)
   End Sub

   Private Shared Sub InsertOrderDetails(orderDetailTable As DataTable)
      ' Use an Object array to insert all the rows .
      ' Values in the array are matched sequentially to the columns, based on the order in which they appear in the table.
      Dim rows As [Object]() = {New [Object]() {1, "O0001", "Mountain Bike", 1419.5, 36}, New [Object]() {2, "O0001", "Road Bike", 1233.6, 16}, New [Object]() {3, "O0001", "Touring Bike", 1653.3, 32}, New [Object]() {4, "O0002", "Mountain Bike", 1419.5, 24}, New [Object]() {5, "O0002", "Road Bike", 1233.6, 12}, New [Object]() {6, "O0003", "Mountain Bike", 1419.5, 48}, _
         New [Object]() {7, "O0003", "Touring Bike", 1653.3, 8}}

      For Each row As [Object]() In rows
         orderDetailTable.Rows.Add(row)
      Next
   End Sub

   Private Shared Sub ShowTable(table As DataTable)
      For Each col As DataColumn In table.Columns
         Console.Write("{0,-14}", col.ColumnName)
      Next
      Console.WriteLine()

      For Each row As DataRow In table.Rows
         For Each col As DataColumn In table.Columns
            If col.DataType.Equals(GetType(DateTime)) Then
               Console.Write("{0,-14:d}", row(col))
            ElseIf col.DataType.Equals(GetType([Decimal])) Then
               Console.Write("{0,-14:C}", row(col))
            Else
               Console.Write("{0,-14}", row(col))
            End If
         Next
         Console.WriteLine()
      Next
      Console.WriteLine()
   End Sub
End Class