获取表示 DataGrid 控件的各列的对象的集合。

[Visual Basic]
Public Overridable ReadOnly Property Columns As _
   DataGridColumnCollection

[C++]
public: __property virtual DataGridColumnCollection* get_Columns();

[JScript]
public function get Columns() : DataGridColumnCollection;

一个 DataGridColumnCollection 对象，该对象包含表示 DataGrid 控件中各列的对象的集合。

使用此属性以编程的方式控制 DataGrid 控件中各列的集合。 Columns 集合包含 DataGrid 控件中呈现的显式声明的列。

注意 显式声明的列可与自动生成的列一起使用。当同时使用这二者时，首先呈现的是显式声明的列，其后是自动生成的列。自动生成的列不会添加到 Columns 集合中。

列在 DataGrid 控件中显示的顺序由列在 Columns 集合中出现的顺序控制。

下表显示从 DataGridColumn 类导出并且可在 Columns 集合中使用的不同列类。

注意 尽管您可以编程的方式将列添加到 Columns 集合，但静态地列出相应列然后使用 Visible 属性显示或隐藏列更容易一些。

示例

[Visual Basic, C#, JScript] 下面的示例展示如何使用 Columns 集合动态向 DataGrid 控件添加列。

[Visual Basic] 
<%@ Page Language="VB" AutoEventWireup="True" %>
<%@ Import Namespace="System.Data" %>
   <script language="VB" runat="server">
    Dim Cart As DataTable
    Dim CartView As DataView
    Function CreateDataSource() As ICollection
        Dim dt As New DataTable()
        Dim dr As DataRow
        dt.Columns.Add(New DataColumn("IntegerValue", GetType(Int32)))
        dt.Columns.Add(New DataColumn("StringValue", GetType(String)))
        dt.Columns.Add(New DataColumn("CurrencyValue", GetType(Double)))
        Dim i As Integer
        For i = 0 To 8
            dr = dt.NewRow()
            dr(0) = i
            dr(1) = "Item " & i.ToString()
            dr(2) = 1.23 *(i + 1)
            dt.Rows.Add(dr)
        Next i
        Dim dv As New DataView(dt)
        Return dv
    End Function 'CreateDataSource
    Sub Page_Load(sender As Object, e As EventArgs)
        If Session("DG4_ShoppingCart") Is Nothing Then
            Cart = New DataTable()
            Cart.Columns.Add(New DataColumn("Item", GetType(String)))
            Cart.Columns.Add(New DataColumn("Price", GetType(String)))
            Session("DG4_ShoppingCart") = Cart
            Cart = CType(Session("DG4_ShoppingCart"), DataTable)
        End If
        CartView = New DataView(Cart)
        ShoppingCart.DataSource = CartView
        ShoppingCart.DataBind()
        If Not IsPostBack Then
            ' Load this data only once.
            ItemsGrid.DataSource = CreateDataSource()
            ItemsGrid.DataBind()
        End If
    End Sub 'Page_Load
    Sub Page_Init(sender As Object, e As EventArgs)
        ' Create a dynamic column to add to Columns collection.
        Dim NumberColumn As New BoundColumn()
        NumberColumn.HeaderText = "Item Number"
        NumberColumn.DataField = "IntegerValue"
        ' Add column to Columns collection.
        ItemsGrid.Columns.AddAt(2, NumberColumn)
    End Sub 'Page_Init
    Sub Grid_CartCommand(sender As Object, e As DataGridCommandEventArgs)
        Dim dr As DataRow = Cart.NewRow()
        ' e.Item is the table row where the command is raised.
        ' For bound columns, the value is stored in the Text property of the TableCell.
        Dim itemCell As TableCell = e.Item.Cells(2)
        Dim priceCell As TableCell = e.Item.Cells(3)
        Dim item As String = itemCell.Text
        Dim price As String = priceCell.Text
        If CType(e.CommandSource, Button).CommandName = "AddToCart" Then
            dr(0) = item
            dr(1) = price
            Cart.Rows.Add(dr)
            'Remove from Cart.
            CartView.RowFilter = "Item='" & item & "'"
            If CartView.Count > 0 Then
                CartView.Delete(0)
            End If
            CartView.RowFilter = ""
        End If
        ShoppingCart.DataBind()
    End Sub 'Grid_CartCommand 
   </script>
   <form runat=server>
      <h3>DataGrid Columns Example</h3>
      <table cellpadding="5">
         <tr valign="top">
               <b>Product List</b>
               <asp:DataGrid id="ItemsGrid"
                    BorderColor="black"
                    BorderWidth="1"
                    CellPadding="3"
                    AutoGenerateColumns="false"
                    OnItemCommand="Grid_CartCommand"
                    runat="server">
                  <HeaderStyle BackColor="#00aaaa">
                  </HeaderStyle>
                  <Columns>
                     <asp:ButtonColumn 
                          HeaderText="Add to cart" 
                          ButtonType="PushButton" 
                          Text="Add" 
                          CommandName="AddToCart"/>
                     <asp:ButtonColumn 
                          HeaderText="Remove from cart" 
                          ButtonType="PushButton" 
                          Text="Remove" 
                          CommandName="RemoveFromCart"/>
                     <asp:BoundColumn 
                          HeaderText="Item" 
                          DataField="StringValue"/>
                     <asp:BoundColumn 
                          HeaderText="Price" 
                          DataField="CurrencyValue" 
                          DataFormatString="{0:c}">
                        <ItemStyle HorizontalAlign="right">
                        </ItemStyle>
                     </asp:BoundColumn>
                  </Columns>
               </asp:DataGrid>
               <b>Shopping Cart</b>
               <asp:DataGrid id="ShoppingCart" 
                    runat="server"
                    BorderColor="black"
                    BorderWidth="1"
                    GridLines="Both"
                    ShowFooter="false"
                    CellPadding="3"
                    CellSpacing="0">
                  <HeaderStyle BackColor="#00aaaa">
                  </HeaderStyle>
                </asp:DataGrid>
      </table>
   </form>
</body>
</html>

[JScript] 
<%@ Page Language="JScript" AutoEventWireup="True" %>
<%@ Import Namespace="System.Data" %>
   <script language="JScript" runat="server">
      var Cart : DataTable = new DataTable();
      var CartView : DataView;   
      function CreateDataSource() : ICollection
         var dt : DataTable = new DataTable();
         var dr : DataRow;
         dt.Columns.Add(new DataColumn("IntegerValue", Int32));
         dt.Columns.Add(new DataColumn("StringValue", System.String));
         dt.Columns.Add(new DataColumn("CurrencyValue", double));
         for (var i : int = 0; i < 9; i++) 
            dr = dt.NewRow();
            dr[0] = i;
            dr[1] = "Item " + i.ToString();
            dr[2] = 1.23 * (i + 1);
            dt.Rows.Add(dr);
         var dv : DataView = new DataView(dt);
         return dv;
      function Page_Load(sender, e : EventArgs) 
         if (Session["DG4_ShoppingCart"] == null) 
            Cart = new DataTable();
            Cart.Columns.Add(new DataColumn("Item", System.String));
            Cart.Columns.Add(new DataColumn("Price", System.String));
            Session["DG4_ShoppingCart"] = Cart;
            Cart = DataTable(Session["DG4_ShoppingCart"]);
         CartView = new DataView(Cart);
         ShoppingCart.DataSource = CartView;
         ShoppingCart.DataBind();
         if (!IsPostBack) 
            // Load this data only once.
            ItemsGrid.DataSource= CreateDataSource();
            ItemsGrid.DataBind();
      function Page_Init(sender, e : EventArgs) 
         // Create a dynamic column to add to Columns collection.
         var NumberColumn : BoundColumn = new BoundColumn();
         NumberColumn.HeaderText="Item Number"; 
         NumberColumn.DataField="IntegerValue";
         // Add column to Columns collection.
         ItemsGrid.Columns.AddAt(2, NumberColumn);
      function Grid_CartCommand(sender, e : DataGridCommandEventArgs) {
         var dr : DataRow = Cart.NewRow();
         // e.Item is the table row where the command is raised.
         // For bound columns, the value is stored in the Text property of the TableCell.
         var itemCell : TableCell = e.Item.Cells[2];
         var priceCell : TableCell = e.Item.Cells[3];
         var item : String = itemCell.Text;
         var price : String = priceCell.Text;
         if ((Button(e.CommandSource)).CommandName == "AddToCart") 
            dr[0] = item;
            dr[1] = price;
            Cart.Rows.Add(dr);
            //Remove from Cart.
            CartView.RowFilter = "Item='" + item + "'";
            if (CartView.Count > 0) 
               CartView.Delete(0);
            CartView.RowFilter = "";
         ShoppingCart.DataBind();
   </script>
   <form runat=server>
      <h3>DataGrid Columns Example</h3>
      <table cellpadding="5">
         <tr valign="top">
               <b>Product List</b>
               <asp:DataGrid id="ItemsGrid"
                    BorderColor="black"
                    BorderWidth="1"
                    CellPadding="3"
                    AutoGenerateColumns="false"
                    OnItemCommand="Grid_CartCommand"
                    runat="server">
                  <HeaderStyle BackColor="#00aaaa">
                  </HeaderStyle>
                  <Columns>
                     <asp:ButtonColumn 
                          HeaderText="Add to cart" 
                          ButtonType="PushButton" 
                          Text="Add" 
                          CommandName="AddToCart"/>
                     <asp:ButtonColumn 
                          HeaderText="Remove from cart" 
                          ButtonType="PushButton" 
                          Text="Remove" 
                          CommandName="RemoveFromCart"/>
                     <asp:BoundColumn 
                          HeaderText="Item" 
                          DataField="StringValue"/>
                     <asp:BoundColumn 
                          HeaderText="Price" 
                          DataField="CurrencyValue" 
                          DataFormatString="{0:c}">
                        <ItemStyle HorizontalAlign="right">
                        </ItemStyle>
                     </asp:BoundColumn>
                  </Columns>
               </asp:DataGrid>
               <b>Shopping Cart</b>
               <asp:DataGrid id="ShoppingCart" 
                    runat="server"
                    BorderColor="black"
                    BorderWidth="1"
                    GridLines="Both"
                    ShowFooter="false"
                    CellPadding="3"
                    CellSpacing="0">
                  <HeaderStyle BackColor="#00aaaa">
                  </HeaderStyle>
                </asp:DataGrid>
      </table>
   </form>
</body>
</html>

[Visual Basic] 
<%@ Page Language="VB" AutoEventWireup="True" %>
<%@ Import Namespace="System.Data" %>
   <script runat="server">
      Function CreateDataSource() As ICollection 
         ' Create sample data for the DataGrid control.
         Dim dt As DataTable = New DataTable()
         Dim dr As DataRow
         ' Define the columns of the table.
         dt.Columns.Add(New DataColumn("IntegerValue", GetType(Int32)))
         dt.Columns.Add(New DataColumn("StringValue", GetType(string)))
         dt.Columns.Add(New DataColumn("CurrencyValue", GetType(double)))
         ' Populate the table with sample values.
         Dim i As Integer
         For i = 0 to 4 
            dr = dt.NewRow()
            dr(0) = i
            dr(1) = "Item " & i.ToString()
            dr(2) = 1.23 * (i + 1)
            dt.Rows.Add(dr)
         Next i
         Dim dv As DataView = New DataView(dt)
         Return dv
      End Function
      Sub Page_Load(sender As Object, e As EventArgs) 
         ' Load sample data only once, when the page is first loaded.
         If Not IsPostBack Then 
            ItemsGrid.DataSource = CreateDataSource()
            ItemsGrid.DataBind()
         End If
      End Sub
      Sub Button_Click(sender As Object, e As EventArgs) 
         ' Count the number of selected items in the DataGrid control.
         Dim count As Integer = 0
         ' Display the selected times.
         Message.Text = "You Selected: <br>"
         ' Iterate through each item (row) in the DataGrid control and
         ' determine whether it is selected.
         Dim item As DataGridItem
         For Each item In ItemsGrid.Items
            DetermineSelection(item, count)        
         ' If no items are selected, display the appropriate message.
         If count = 0 Then
            Message.Text = "No items selected"
         End If
      End Sub
      Sub DetermineSelection(item As DataGridItem, ByRef count As Integer)
         ' Retrieve the SelectCheckBox CheckBox control from the 
         ' specified item (row) in the DataGrid control.
         Dim selection As CheckBox = _
             CType(item.FindControl("SelectCheckBox"), CheckBox)
         ' If the item is selected, display the appropriate message and
         ' increment the count of selected items.
         If Not selection Is Nothing Then
           If selection.Checked Then
              Message.Text &= "- " & item.Cells(1).Text & "<br>"
              count = count + 1
           End If
         End If    
      End Sub
      Sub Check_Change(sender As Object, e As EventArgs)
         ' Show or hide the first column depending on the value of
         ' the check box.
         If ShowCheckBox.Checked Then
            ItemsGrid.Columns(0).Visible = True
            ItemsGrid.Columns(0).Visible = False
         End If
      End Sub
   </script>
   <form runat=server>
      <h3>DataGridColumn Visible Example</h3>
      Select whether to show or hide the first column.
      <br><br>
      <b>Product List</b>
      <asp:DataGrid id="ItemsGrid"
           BorderColor="black"
           BorderWidth="1"
           CellPadding="3"
           ShowFooter="True"
           AutoGenerateColumns="False"
           runat="server">
         <HeaderStyle BackColor="#00aaaa">
         </HeaderStyle>
         <FooterStyle BackColor="#00aaaa">
         </FooterStyle>
         <Columns>
            <asp:BoundColumn DataField="IntegerValue"
                 Visible="True" 
                 HeaderText="Item"/>
            <asp:BoundColumn DataField="StringValue"
                 Visible="True"  
                 HeaderText="Description"/>
            <asp:BoundColumn DataField="CurrencyValue"
                 Visible="True"  
                 HeaderText="Price"
                 DataFormatString="{0:c}">
               <ItemStyle HorizontalAlign="Right">
               </ItemStyle>
            </asp:BoundColumn>
            <asp:TemplateColumn HeaderText="Select Item"
                 Visible="True" >
               <ItemTemplate>
                  <asp:CheckBox id="SelectCheckBox"
                       Text="Add to Cart"
                       Checked="False"
                       runat="server"/>
               </ItemTemplate>
            </asp:TemplateColumn>
         </Columns> 
      </asp:DataGrid>
      <br><br>
      <asp:Button id="SubmitButton"
           Text="Submit"
           OnClick = "Button_Click"
           runat="server"/>
      <br><br>
      <asp:Label id="Message"
           runat="server"/>
      <asp:CheckBox id="ShowCheckBox"
           Text="Show first column"
           AutoPostBack="True"
           OnCheckedChanged="Check_Change"
           Checked="True"
           runat="server"/>
   </form>
</body>
</html>

[C++] 没有可用于 C++ 的示例。若要查看 Visual Basic、C# 或 JScript 示例，请单击页左上角的“语言筛选器”按钮 。

平台: Windows 2000, Windows XP Professional, Windows Server 2003 系列

DataGrid 类 | DataGrid 成员 | System.Web.UI.WebControls 命名空间 | DataGridColumn | BoundColumn | ButtonColumn | EditCommandColumn | HyperLinkColumn | TemplateColumn | DataGrid 成员（Visual J# 语法） | C++ 托管扩展编程

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