DataKeyCollection DataKeyCollection DataKeyCollection DataKeyCollection Class

定义

表示包含数据源中每个记录的键字段的集合。Represents a collection that contains the key field of each record in a data source. 此类不能被继承。This class cannot be inherited.

public ref class DataKeyCollection sealed : System::Collections::ICollection
public sealed class DataKeyCollection : System.Collections.ICollection
type DataKeyCollection = class
    interface ICollection
    interface IEnumerable
Public NotInheritable Class DataKeyCollection
Implements ICollection
继承
DataKeyCollectionDataKeyCollectionDataKeyCollectionDataKeyCollection
实现

示例


<%@ Page Language="C#" AutoEventWireup="True" %>
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.SqlClient" %>

<!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" >

<head runat="server">
    <title>BaseDataList DataKeys Example</title>
<script runat="server">

      ICollection CreateDataSource() 
      {
      
         // Create sample data for the DataGrid control.
         DataTable dt = new DataTable();
         DataRow dr;
 
         // Define the columns of the table.
         dt.Columns.Add(new DataColumn("IntegerValue", typeof(Int32)));
         dt.Columns.Add(new DataColumn("StringValue", typeof(string)));
         dt.Columns.Add(new DataColumn("CurrencyValue", typeof(double)));

         // Define the primary key for the table as the IntegerValue 
         // column (column 0). To do this, first create an array of 
         // DataColumns to represent the primary key. The primary key can
         // consist of multiple columns, but in this example, only
         // one column is used.
         DataColumn[] keys = new DataColumn[1];
         keys[0] = dt.Columns[0];

         // Then assign the array to the PrimaryKey property of the DataTable. 
         dt.PrimaryKey = keys;
 
         // Populate the table with sample values.
         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);
         }

         // To persist the data source between posts to the server, 
         // store it in session state.  
         Session["Source"] = dt;
 
         DataView dv = new DataView(dt);
         return dv;

      }
 
      void Page_Load(Object sender, EventArgs e) 
      {
 
         // Load sample data only once, when the page is first loaded.
         if (!IsPostBack) 
         {
            ItemsGrid.DataSource = CreateDataSource();
            ItemsGrid.DataBind();
         }

      }

      void Delete_Command(Object sender, DataGridCommandEventArgs e)
      {

         // Retrieve the data table from session state.
         DataTable dt = (DataTable)Session["Source"];

         // Retrieve the data row to delete from the data table. 
         // Use the DataKeys property of the DataGrid control to get 
         // the primary key value of the selected row. 
         // Search the Rows collection of the data table for this value. 
         DataRow row;
         row = dt.Rows.Find(ItemsGrid.DataKeys[e.Item.ItemIndex]);

         // Delete the item selected in the DataGrid from the data source.
         if(row != null)
         {
            dt.Rows.Remove(row);
         }

         // Save the data source.
         Session["Source"] = dt;

         // Create a DataView and bind it to the DataGrid control.
         DataView dv = new DataView(dt);
         ItemsGrid.DataSource = dv;
         ItemsGrid.DataBind();

      }

   </script>

</head>

<body>

   <form id="form1" runat="server">

      <h3>BaseDataList DataKeys Example</h3>

      <asp:DataGrid id="ItemsGrid" 
           BorderColor="Black"
           ShowFooter="False" 
           CellPadding="3" 
           CellSpacing="0"
           HeaderStyle-BackColor="#aaaadd"
           DataKeyField="IntegerValue"
           OnDeleteCommand="Delete_Command"
           runat="server">

         <Columns>

            <asp:ButtonColumn Text="Delete"
                 CommandName="Delete"/>

         </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" >

<head runat="server">
    <title>BaseDataList DataKeys and DataKeyField Example</title>
<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(Integer)))
         dt.Columns.Add(new DataColumn("StringValue", GetType(String)))
         dt.Columns.Add(new DataColumn("CurrencyValue", GetType(Double)))

         ' Define the primary key for the table as the IntegerValue 
         ' column (column 0). To do this, first create an array of 
         ' DataColumns to represent the primary key. The primary key can
         ' consist of multiple columns, but in this example, only
         ' one column is used.
         Dim keys(1) As DataColumn
         keys(0) = dt.Columns(0)

         ' Then assign the array to the PrimaryKey property of the DataTable. 
         dt.PrimaryKey = keys
 
         ' Populate the table with sample values.
         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

         ' To persist the data source between posts to the server, 
         ' store it in session state.  
         Session("Source") = dt
 
         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 Delete_Command(sender As Object, e As DataGridCommandEventArgs)

         ' Retrieve the data table from session state.
         Dim dt As DataTable = CType(Session("Source"), DataTable)

         ' Retrieve the data row to delete from the data table. 
         ' Use the DataKeys property of the DataGrid control to get 
         ' the primary key value of the selected row. 
         ' Search the Rows collection of the data table for this value. 
         Dim row As DataRow
         row = dt.Rows.Find(ItemsGrid.DataKeys(e.Item.ItemIndex))

         ' Delete the item selected in the DataGrid from the data source.
         If Not row is Nothing Then
         
            dt.Rows.Remove(row)
         
         End If

         ' Save the data source.
         Session("Source") = dt

         ' Create a DataView and bind it to the DataGrid control.
         Dim dv As DataView = New DataView(dt)
         ItemsGrid.DataSource = dv
         ItemsGrid.DataBind()

      End Sub

   </script>

</head>

<body>

   <form id="form1" runat="server">

      <h3>BaseDataList DataKeys and DataKeyField Example</h3>

      <asp:DataGrid id="ItemsGrid" 
           BorderColor="Black"
           ShowFooter="False" 
           CellPadding="3" 
           CellSpacing="0"
           HeaderStyle-BackColor="#aaaadd"
           DataKeyField="IntegerValue"
           OnDeleteCommand="Delete_Command"
           runat="server">

         <Columns>

            <asp:ButtonColumn Text="Delete"
                 CommandName="Delete"/>

         </Columns>

      </asp:DataGrid>

   </form>

</body>
</html>

注解

DataKeyCollection类表示数据源中的键字段的集合。The DataKeyCollection class represents a collection of the key fields in the data source. 数据源中每条记录的键字段存储在此集合中。The key field of each record in the data source is stored in this collection. 这样, 便可以在不显示控件的情况下, 用数据列表控件来存储键字段。This allows you to store the key field with a data listing control without displaying it in the control. 此集合使用BaseDataList.DataKeyField属性所指定的字段中的值自动填充。This collection is automatically filled with the values from the field specified by the BaseDataList.DataKeyField property. 此集合不允许您手动添加或删除集合中的项。This collection does not allow you to manually add or remove items from the collection.

在事件ItemCommand的处理程序中 (如或DeleteCommand), 通常使用 key 字段来修改数据源中的特定记录。The key field is commonly used in a handler for an event, such as ItemCommand or DeleteCommand, as part of an update query string to revise a specific record in the data source. Key 字段有助于更新查询字符串标识要修改的相应记录。The key field helps the update query string identify the appropriate record to modify.

Count使用属性可确定集合中的项数。Use the Count property to determine the number of items in the collection. 若要以编程方式检索中DataKeyCollection的密钥字段, 请使用以下方法之一:To programmatically retrieve a key field from a DataKeyCollection, use one of following methods:

  • 使用数组表示法, 使用索引器获取集合中的单个键字段。Use the indexer to get a single key field from the collection, using array notation.

  • 使用方法可将集合的内容复制System.Array到对象, 然后可以使用该对象从集合中获取项。 CopyToUse the CopyTo method to copy the contents of the collection to a System.Array object, which can then be used to get items from the collection.

  • 使用方法可创建实现的System.Collections.IEnumerator对象, 然后可以使用该对象从集合中获取项。 GetEnumeratorUse the GetEnumerator method to create a System.Collections.IEnumerator implemented object, which can then be used to get items from the collection.

构造函数

DataKeyCollection(ArrayList) DataKeyCollection(ArrayList) DataKeyCollection(ArrayList) DataKeyCollection(ArrayList)

初始化 DataKeyCollection 类的新实例。Initializes a new instance of the DataKeyCollection class.

属性

Count Count Count Count

获取集合中的项数。Gets the number of items in the collection.

IsReadOnly IsReadOnly IsReadOnly IsReadOnly

获取一个值,该值指示是否可以修改 DataKeyCollection 中的项。Gets a value indicating whether items in the DataKeyCollection can be modified.

IsSynchronized IsSynchronized IsSynchronized IsSynchronized

获取一个值,该值指示 DataKeyCollection 是否是同步的(线程安全)。Gets a value indicating whether the DataKeyCollection is synchronized (thread-safe).

Item[Int32] Item[Int32] Item[Int32] Item[Int32]

获取集合中位于指定索引处的键字段。Gets the key field at the specified index in the collection.

SyncRoot SyncRoot SyncRoot SyncRoot

获取用于同步对 DataKeyCollection 的访问的对象。Gets the object used to synchronize access to the DataKeyCollection.

方法

CopyTo(Array, Int32) CopyTo(Array, Int32) CopyTo(Array, Int32) CopyTo(Array, Int32)

DataKeyCollection 对象中的指定索引位置开始,将 Array 中的所有项复制到指定的 Array 对象。Copies all the items from the DataKeyCollection to the specified Array object, starting at the specified index in the Array object.

Equals(Object) Equals(Object) Equals(Object) Equals(Object)

确定指定的对象是否等于当前对象。Determines whether the specified object is equal to the current object.

(Inherited from Object)
GetEnumerator() GetEnumerator() GetEnumerator() GetEnumerator()

创建实现了 IEnumerator 的对象,它包含 DataKeyCollection 中的所有键字段。Creates a IEnumerator implemented object that contains all key fields in the DataKeyCollection.

GetHashCode() GetHashCode() GetHashCode() GetHashCode()

作为默认哈希函数。Serves as the default hash function.

(Inherited from Object)
GetType() GetType() GetType() GetType()

获取当前实例的 TypeGets the Type of the current instance.

(Inherited from Object)
MemberwiseClone() MemberwiseClone() MemberwiseClone() MemberwiseClone()

创建当前 Object 的浅表副本。Creates a shallow copy of the current Object.

(Inherited from Object)
ToString() ToString() ToString() ToString()

返回表示当前对象的字符串。Returns a string that represents the current object.

(Inherited from Object)

扩展方法

Cast<TResult>(IEnumerable) Cast<TResult>(IEnumerable) Cast<TResult>(IEnumerable) Cast<TResult>(IEnumerable)

IEnumerable 的元素强制转换为指定的类型。Casts the elements of an IEnumerable to the specified type.

OfType<TResult>(IEnumerable) OfType<TResult>(IEnumerable) OfType<TResult>(IEnumerable) OfType<TResult>(IEnumerable)

根据指定类型筛选 IEnumerable 的元素。Filters the elements of an IEnumerable based on a specified type.

AsParallel(IEnumerable) AsParallel(IEnumerable) AsParallel(IEnumerable) AsParallel(IEnumerable)

启用查询的并行化。Enables parallelization of a query.

AsQueryable(IEnumerable) AsQueryable(IEnumerable) AsQueryable(IEnumerable) AsQueryable(IEnumerable)

IEnumerable 转换为 IQueryableConverts an IEnumerable to an IQueryable.

适用于

另请参阅