通过

DataGridColumnCollection.Clear 方法

  • 参考

定义

命名空间:
System.Web.UI.WebControls
程序集:
System.Web.dll

从 DataGridColumn 集合中移除所有由 DataGridColumnCollection 导出的列对象。

public:
 void Clear();
public void Clear ();
member this.Clear : unit -> unit
Public Sub Clear ()

示例

下面的代码示例演示如何在向集合添加新列之前使用 Clear 该方法清空 DataGridColumnCollection 集合。

<%@ Page Language="C#" AutoEventWireup="True" %>
<%@ Import Namespace="System.Data" %>
 
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
   <script language="C#" runat="server">
 
      ICollection CreateDataSource() 
      {
         DataTable dt = new DataTable();
         DataRow dr;
 
         dt.Columns.Add(new DataColumn("IntegerValue", typeof(Int32)));
         dt.Columns.Add(new DataColumn("StringValue", typeof(string)));
         dt.Columns.Add(new DataColumn("CurrencyValue", typeof(double)));
 
         for (int i = 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);
         }
 
         DataView dv = new DataView(dt);
         return dv;
      }

      void Page_Init(Object sender, EventArgs e) 
      {

         // Empty DataGridColumnsCollection collection. 
         ItemsGrid.Columns.Clear();

         // Create dynamic columns to add to Columns collection.
         BoundColumn IntegerColumn = new BoundColumn();
         BoundColumn StringColumn = new BoundColumn();
         BoundColumn PriceColumn = new BoundColumn();

         IntegerColumn.HeaderText="Item Number"; 
         IntegerColumn.DataField="IntegerValue";

         StringColumn.HeaderText="Item"; 
         StringColumn.DataField="StringValue";

         PriceColumn.HeaderText="Price"; 
         PriceColumn.DataField="CurrencyValue";

         // Add columns to Columns collection.
         ItemsGrid.Columns.Add(IntegerColumn);
         ItemsGrid.Columns.Add(StringColumn);
         ItemsGrid.Columns.Add(PriceColumn);

      } 
 
      void Page_Load(Object sender, EventArgs e) 
      {
 
         if (!IsPostBack) 
         {
            // Load this data only once.
            ItemsGrid.DataSource= CreateDataSource();
            ItemsGrid.DataBind();
         }

      }
   
   </script>
 
<head runat="server">
    <title>DataGridColumnCollection Clear Example</title>
</head>
<body>
 
   <form id="form1" runat="server">
 
      <h3>DataGridColumnCollection Clear Example</h3>
 
      <b>Product List</b>
 
      <asp:DataGrid id="ItemsGrid"
           BorderColor="black"
           BorderWidth="1"
           CellPadding="3"
           AutoGenerateColumns="false"
           runat="server">

         <HeaderStyle BackColor="#00aaaa">
         </HeaderStyle>
 
         <Columns>
                  
            <asp:BoundColumn 
                 HeaderText="Item Number" 
                 DataField="IntegerValue"/>
 
            <asp:BoundColumn 
                 HeaderText="Item" 
                 DataField="StringValue"/>
 
            <asp:BoundColumn 
                 HeaderText="Price" 
                 DataField="CurrencyValue" 
                 DataFormatString="{0:c}">

               <ItemStyle HorizontalAlign="right">
               </ItemStyle>

            </asp:BoundColumn>
 
         </Columns>
   
      </asp:DataGrid>    
 
   </form>
 
</body>
</html>

<%@ Page Language="VB" AutoEventWireup="True" %>
<%@ Import Namespace="System.Data" %>
 
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
   <script language="VB" runat="server">
 
        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_Init(sender As Object, e As EventArgs)
            
            ' Empty DataGridColumnsCollection collection. 
            ItemsGrid.Columns.Clear()
            
            ' Create dynamic columns to add to Columns collection.
            Dim IntegerColumn As New BoundColumn()
            Dim StringColumn As New BoundColumn()
            Dim PriceColumn As New BoundColumn()
            
            IntegerColumn.HeaderText = "Item Number"
            IntegerColumn.DataField = "IntegerValue"
            
            StringColumn.HeaderText = "Item"
            StringColumn.DataField = "StringValue"
            
            PriceColumn.HeaderText = "Price"
            PriceColumn.DataField = "CurrencyValue"
            
            ' Add columns to Columns collection.
            ItemsGrid.Columns.Add(IntegerColumn)
            ItemsGrid.Columns.Add(StringColumn)
            ItemsGrid.Columns.Add(PriceColumn)

        End Sub 'Page_Init
         

        Sub Page_Load(sender As Object, e As EventArgs)
            
            If Not IsPostBack Then

                ' Load this data only once
                ItemsGrid.DataSource = CreateDataSource()
                ItemsGrid.DataBind()

            End If
        End Sub 'Page_Load 
   
   </script>
 
<head runat="server">
    <title>DataGridColumnCollection Clear Example</title>
</head>
<body>
 
   <form id="form1" runat="server">
 
      <h3>DataGridColumnCollection Clear Example</h3>
 
      <b>Product List</b>
 
      <asp:DataGrid id="ItemsGrid"
           BorderColor="black"
           BorderWidth="1"
           CellPadding="3"
           AutoGenerateColumns="false"
           runat="server">

         <HeaderStyle BackColor="#00aaaa">
         </HeaderStyle>
 
         <Columns>
                  
            <asp:BoundColumn 
                 HeaderText="Item Number" 
                 DataField="IntegerValue"/>
 
            <asp:BoundColumn 
                 HeaderText="Item" 
                 DataField="StringValue"/>
 
            <asp:BoundColumn 
                 HeaderText="Price" 
                 DataField="CurrencyValue" 
                 DataFormatString="{0:c}">

               <ItemStyle HorizontalAlign="right">
               </ItemStyle>

            </asp:BoundColumn>
 
         </Columns>
   
      </asp:DataGrid>    
 
   </form>
 
</body>
</html>

注解

使用此方法从集合中删除所有 DataGridColumn派生列对象 DataGridColumnCollection 。

备注

使用此方法后，该 Count 属性会自动设置为 0 该属性。

适用于

另请参阅