DataKey Class

Reference

Definition

Namespace:: System.Web.UI.WebControls

Assembly:: System.Web.dll

Important

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

Represents the primary key field or fields of a record in a data-bound control.

public ref class DataKey : System::Web::UI::IStateManager

public ref class DataKey : IEquatable<System::Web::UI::WebControls::DataKey ^>, System::Web::UI::IStateManager

public class DataKey : System.Web.UI.IStateManager

public class DataKey : IEquatable<System.Web.UI.WebControls.DataKey>, System.Web.UI.IStateManager

type DataKey = class
    interface IStateManager

type DataKey = class
    interface IStateManager
    interface IEquatable<DataKey>

Public Class DataKey
Implements IStateManager

Public Class DataKey
Implements IEquatable(Of DataKey), IStateManager

Inheritance: Object
DataKey

Implements: IStateManager IEquatable<DataKey>

Examples

The following code example demonstrates how to determine the primary key value of a record in a DetailsView control using the Value property of a DataKey object.


<%@ Page language="C#" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">

  void CustomerDetailsView_DataBound(Object sender, EventArgs e)
  {
    // Get the DataKey object for the current record.
    DataKey key = CustomerDetailsView.DataKey;
    
    // Display the value of the key field.
    MessageLabel.Text = "The key field value for the displayed record is " + 
      key.Value.ToString() + ".";
  }
  
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >

  <head runat="server">
    <title>DataKey Example</title>
</head>
<body>
    <form id="form1" runat="server">
        
      <h3>DataKey Example</h3>
                       
        <asp:detailsview id="CustomerDetailsView"
          datasourceid="DetailsViewSource"
          autogeneraterows="true"
          datakeynames="CustomerID"  
          allowpaging="true"
          ondatabound="CustomerDetailsView_DataBound" 
          runat="server">
            
        </asp:detailsview>
        
        <br/>
        
        <asp:label id="MessageLabel"
          forecolor="Red"
          runat="server"/>
            
        <!-- This example uses Microsoft SQL Server and connects  -->
        <!-- to the Northwind sample database. Use an ASP.NET     -->
        <!-- expression to retrieve the connection string value   -->
        <!-- from the Web.config file.                            -->
        <asp:sqldatasource id="DetailsViewSource"
          selectcommand="Select [CustomerID], [CompanyName], [Address], [City], [PostalCode], [Country] From [Customers]"
          connectionstring="<%$ ConnectionStrings:NorthWindConnectionString%>" 
          runat="server"/>
            
      </form>
  </body>
</html>


<%@ Page language="VB" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">

  Sub CustomerDetailsView_DataBound(ByVal sender As Object, ByVal e As EventArgs) Handles CustomerDetailsView.DataBound

    ' Get the DataKey object for the current record.
    Dim key As DataKey = CustomerDetailsView.DataKey
    
    ' Display the value of the key field.
    MessageLabel.Text = "The key field value for the displayed record is " & _
      key.Value.ToString() & "."
    
  End Sub
  
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >

  <head runat="server">
    <title>DataKey Example</title>
</head>
<body>
    <form id="form1" runat="server">
        
      <h3>DataKey Example</h3>
                       
        <asp:detailsview id="CustomerDetailsView"
          datasourceid="DetailsViewSource"
          autogeneraterows="true"
          datakeynames="CustomerID"  
          allowpaging="true"
          runat="server">
            
        </asp:detailsview>
        
        <br/>
        
        <asp:label id="MessageLabel"
          forecolor="Red"
          runat="server"/>
            
        <!-- This example uses Microsoft SQL Server and connects  -->
        <!-- to the Northwind sample database. Use an ASP.NET     -->
        <!-- expression to retrieve the connection string value   -->
        <!-- from the Web.config file.                            -->
        <asp:sqldatasource id="DetailsViewSource"
          selectcommand="Select [CustomerID], [CompanyName], [Address], [City], [PostalCode], [Country] From [Customers]"
          connectionstring="<%$ ConnectionStrings:NorthWindConnectionString%>" 
          runat="server"/>
            
      </form>
  </body>
</html>

Remarks

The DataKey class is used to represent the primary key for a record in a data-bound control. The primary key for a record can be composed of one of more fields from the data source. Although the DataKey class is not a collection, it can store multiple key field values. The key field values are populated when one of the constructors for the DataKey class is called. You can retrieve a key field value from a DataKey object in the following ways:

Use the DataKey.Item[Int32] property to retrieve a key field value at a specific index in the DataKey object.
Use the DataKey.Item[String] property to retrieve a key field value of a specific field.
Use the Value property to retrieve the value of the key field at index 0 in the DataKey object. This property is often used as a shortcut to retrieve the key value of a record when the primary key contains only one field.
Use the Values property to create an IOrderedDictionary object that can be used to iterate through the key field values.

In general, DataKey objects are automatically generated by data-bound controls when the control's DataKeyNames property is set. The DataKey objects contain the values of the key field or fields specified in the DataKeyNames property. Data-bound controls that display a single record at a time (such as DetailsView or FormView) generally store the DataKey object for the current record displayed in the DataKey property of the control. Data-bound controls that display multiple records at a time (such as GridView) generally store the DataKey objects for each record in the control in a DataKeyArray collection. The DataKeyArray collection is then stored in the DataKeys property of the control.

Constructors

DataKey(IOrderedDictionary)	Initializes a new instance of the DataKey class using the specified dictionary of key field values.
DataKey(IOrderedDictionary, String[])	Initializes a new instance of the DataKey class using the specified dictionary of key field values and array of field names.

Properties

IsTrackingViewState	Gets a value indicating whether the DataKey object is tracking its view-state changes.
Item[Int32]	Gets the value of the key field at the specified index from a DataKey object.
Item[String]	Gets the value of the key field with the specified field name from a DataKey object.
Value	Gets the value of the key field at index 0 in the DataKey object.
Values	Gets an IOrderedDictionary object that contains every key field in the DataKey object.

Methods

Equals(DataKey)	Determines whether the specified DataKey array is equal to the current data key.
Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetType()	Gets the Type of the current instance. (Inherited from Object)
LoadViewState(Object)	Loads the previously saved view state of the DataKey object.
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
SaveViewState()	Saves the current view state of the DataKey object.
ToString()	Returns a string that represents the current object. (Inherited from Object)
TrackViewState()	Marks the starting point at which to begin tracking and saving view-state changes to the DataKey object.

Explicit Interface Implementations

IStateManager.IsTrackingViewState	Gets a value indicating whether the DataKey object is tracking its view-state changes.
IStateManager.LoadViewState(Object)	Loads the previously saved view state of the DataKey object.
IStateManager.SaveViewState()	Saves the current view state of the DataKey object.
IStateManager.TrackViewState()	Marks the starting point at which to begin tracking and saving view-state changes to the DataKey object.

Applies to

Bagikan melalui