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ObjectDataSource.SqlCacheDependency Propriedade

Definição

Obtém ou define uma cadeia de caracteres separada por ponto-e-vírgula que indica quais bancos de dados e tabelas usar para a dependência de cache do Microsoft SQL Server.

public:
 virtual property System::String ^ SqlCacheDependency { System::String ^ get(); void set(System::String ^ value); };
public virtual string SqlCacheDependency { get; set; }
member this.SqlCacheDependency : string with get, set
Public Overridable Property SqlCacheDependency As String

Valor da propriedade

Uma cadeia de caracteres que indica quais bancos de dados e tabelas usar para a dependência de cache do SQL Server.

Exemplos

Esta seção contém dois exemplos de código. O primeiro exemplo de código demonstra como criar uma dependência de cache do SQL Server e definir a SqlCacheDependency propriedade de um ObjectDataSource objeto . O segundo exemplo de código demonstra como implementar um método wrapper que retorna um DataSet objeto para habilitar o cache e a filtragem com um ObjectDataSource objeto .

O exemplo de código a seguir demonstra como criar uma dependência de cache do SQL Server e definir a SqlCacheDependency propriedade de um ObjectDataSource controle . Neste exemplo, o banco de dados é sondado a cada 120 segundos. Se os dados na tabela Funcionários da Northwind Traders forem alterados durante esse período, todos os ObjectDataSource dados armazenados em cache pelo controle e exibidos pelo GridView controle expirarão e um novo conjunto de dados será recuperado na próxima solicitação para a página.

<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.CS" Assembly="Samples.AspNet.CS" %>
<%@ Page language="c#" %>

<!--
The page uses an example configuration that includes
connection strings and a defined SqlCacheDependecy.

<?xml version="1.0"?>
<configuration>

  <connectionStrings>
    <add name="MyNorthwind"
         connectionString="Data Source="localhost";Integrated Security="SSPI";Initial Catalog="Northwind""
         providerName="System.Data.SqlClient" />
  </connectionStrings>

  <system.web>
    <cache>
      <sqlCacheDependency enabled="true">
        <databases>
          <add
            name="Northwind"
            connectionStringName="MyNorthwind"
            pollTime="120000" />
        </databases>
      </sqlCacheDependency>
    </cache>

  </system.web>
</configuration>
-->



<!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>
    <title>ObjectDataSource - C# Example</title>
  </head>
  <body>
    <form id="Form1" method="post" runat="server">

        <asp:gridview
          id="GridView1"
          runat="server"
          datasourceid="ObjectDataSource1" />

        <asp:objectdatasource
          id="ObjectDataSource1"
          runat="server"
          typename="Samples.AspNet.CS.EmployeeLogic"
          selectmethod="GetAllEmployeesAsDataSet"
          enablecaching="True"
          cacheduration="300"
          cacheexpirationpolicy="Absolute"
          sqlcachedependency="Northwind:Employees" />

    </form>
  </body>
</html>
<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.VB" Assembly="Samples.AspNet.VB" %>
<%@ Page language="vb" %>

<!--

The page uses an example configuration that includes
connection strings and a defined SqlCacheDependecy.

<?xml version="1.0"?>
<configuration>

  <connectionStrings>
    <add name="MyNorthwind"
         connectionString="Data Source="localhost";Integrated Security="SSPI";Initial Catalog="Northwind""
         providerName="System.Data.SqlClient" />
  </connectionStrings>

  <system.web>
    <cache>
      <sqlCacheDependency enabled="true">
        <databases>
          <add
            name="Northwind"
            connectionStringName="MyNorthwind"
            pollTime="120000" />
        </databases>
      </sqlCacheDependency>
    </cache>

  </system.web>
</configuration>
-->



<!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>
    <title>ObjectDataSource - VB Example</title>
  </head>
  <body>
    <form id="Form1" method="post" runat="server">

        <asp:gridview
          id="GridView1"
          runat="server"
          datasourceid="ObjectDataSource1" />

        <asp:objectdatasource
          id="ObjectDataSource1"
          runat="server"
          typename="Samples.AspNet.VB.EmployeeLogic"
          selectmethod="GetAllEmployeesAsDataSet"
          enablecaching="True"
          cacheduration="300"
          cacheexpirationpolicy="Absolute"
          sqlcachedependency="Northwind:Employees" />

    </form>
  </body>
</html>

O exemplo de código a seguir demonstra como implementar um método wrapper que retorna um DataSet objeto para habilitar o cache e a filtragem com um ObjectDataSource controle . Na implementação base da EmployeeLogic classe , o GetAllEmployees método retorna um ArrayList objeto . Em vez de refatorar completamente o objeto para trabalhar com o em uma página do ObjectDataSource Web Forms, um método wrapper chamado GetAllEmployeesAsDataSet é adicionado que retorna um conjunto de NorthwindEmployee dados como um DataSet.

namespace Samples.AspNet.CS {

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Web.UI;
using System.Web.UI.WebControls;
  //
  // EmployeeLogic is a stateless business object that encapsulates
  // the operations one can perform on a NorthwindEmployee object.
  //
  public class EmployeeLogic {

    // Returns a collection of NorthwindEmployee objects.
    public static ICollection GetAllEmployees () {
      ArrayList al = new ArrayList();

      ConnectionStringSettings cts = ConfigurationManager.ConnectionStrings["NorthwindConnection"];

      SqlDataSource sds
        = new SqlDataSource(cts.ConnectionString,
                            "SELECT EmployeeID FROM Employees");
      try {
        IEnumerable IDs = sds.Select(DataSourceSelectArguments.Empty);

        // Iterate through the Enumeration and create a
        // NorthwindEmployee object for each ID.
        IEnumerator enumerator = IDs.GetEnumerator();
        while (enumerator.MoveNext()) {
          // The IEnumerable contains DataRowView objects.
          DataRowView row = enumerator.Current as DataRowView;
          string id = row["EmployeeID"].ToString();
          NorthwindEmployee nwe = new NorthwindEmployee(id);
          // Add the NorthwindEmployee object to the collection.
          al.Add(nwe);
        }
      }
      finally {
        // If anything strange happens, clean up.
        sds.Dispose();
      }

      return al;
    }

    //
    // To support basic filtering, the employees cannot
    // be returned as an array of objects, rather as a
    // DataSet of the raw data values.
    public static DataSet GetAllEmployeesAsDataSet () {
      ICollection employees = GetAllEmployees();

      DataSet ds = new DataSet("Table");

      // Create the schema of the DataTable.
      DataTable dt = new DataTable();
      DataColumn dc;
      dc = new DataColumn("FirstName", typeof(string)); dt.Columns.Add(dc);
      dc = new DataColumn("LastName",  typeof(string)); dt.Columns.Add(dc);
      dc = new DataColumn("Title",     typeof(string)); dt.Columns.Add(dc);
      dc = new DataColumn("Courtesy",  typeof(string)); dt.Columns.Add(dc);
      dc = new DataColumn("Supervisor",typeof(Int32));  dt.Columns.Add(dc);

      // Add rows to the DataTable.
      IEnumerator emplEnum = employees.GetEnumerator();
      DataRow row;
      NorthwindEmployee ne;
      while (emplEnum.MoveNext()) {
        ne = emplEnum.Current as NorthwindEmployee;
        row = dt.NewRow();
        row["FirstName"]  = ne.FirstName;
        row["LastName"]   = ne.LastName;
        row["Title"]      = ne.Title;
        row["Courtesy"]   = ne.Courtesy;
        row["Supervisor"] = ne.Supervisor;
        dt.Rows.Add(row);
      }
      // Add the complete DataTable to the DataSet.
      ds.Tables.Add(dt);

      return ds;
    }
    public static NorthwindEmployee GetEmployee(object anID) {
      if (anID.Equals("-1") ||
          anID.Equals(DBNull.Value) ) {
        return new NorthwindEmployee();
      }
      else {
        return new NorthwindEmployee(anID);
      }
    }

    public static void UpdateEmployeeInfo(NorthwindEmployee ne) {
      bool retval = ne.Save();
      if (! retval) { throw new NorthwindDataException("UpdateEmployee failed."); }
    }

    public static void DeleteEmployee(NorthwindEmployee ne) {
      bool retval = ne.Delete();
      if (! retval) { throw new NorthwindDataException("DeleteEmployee failed."); }
    }
  }

  public class NorthwindEmployee {

    public NorthwindEmployee () {
      ID = DBNull.Value;
      lastName = "";
      firstName = "";
      title="";
      titleOfCourtesy = "";
      reportsTo = -1;
    }

    public NorthwindEmployee (object anID) {
      this.ID = anID;

      SqlConnection conn
        = new SqlConnection (ConfigurationManager.ConnectionStrings["NorthwindConnection"].ConnectionString);
      SqlCommand sc =
        new SqlCommand(" SELECT FirstName,LastName,Title,TitleOfCourtesy,ReportsTo " +
                       " FROM Employees " +
                       " WHERE EmployeeID = @empId",
                       conn);
      // Add the employee ID parameter and set its value.
      sc.Parameters.Add(new SqlParameter("@empId",SqlDbType.Int)).Value = Int32.Parse(anID.ToString());
      SqlDataReader sdr = null;

      try {
        conn.Open();
        sdr = sc.ExecuteReader();

        // Only loop once.
        if (sdr != null && sdr.Read()) {
          // The IEnumerable contains DataRowView objects.
          this.firstName        = sdr["FirstName"].ToString();
          this.lastName         = sdr["LastName"].ToString();
          this.title            = sdr["Title"].ToString();
          this.titleOfCourtesy  = sdr["TitleOfCourtesy"].ToString();
          if (! sdr.IsDBNull(4)) {
            this.reportsTo        = sdr.GetInt32(4);
          }
        }
        else {
          throw new NorthwindDataException("Data not loaded for employee id.");
        }
      }
      finally {
        try {
          if (sdr != null) sdr.Close();
          conn.Close();
        }
        catch (SqlException) {
          // Log an event in the Application Event Log.
          throw;
        }
      }
    }

    private object ID;
    public string EmpID {
      get { return ID.ToString();  }
    }

    private string lastName;
    public string LastName {
      get { return lastName; }
      set { lastName = value; }
    }

    private string firstName;
    public string FirstName {
      get { return firstName; }
      set { firstName = value;  }
    }

    public string FullName {
      get { return FirstName + " " + LastName; }
    }

    private string title;
    public String Title {
      get { return title; }
      set { title = value; }
    }

    private string titleOfCourtesy;
    public string Courtesy {
      get { return titleOfCourtesy; }
      set { titleOfCourtesy = value; }
    }

    private int    reportsTo;
    public int Supervisor {
      get { return reportsTo; }
      set { reportsTo = value; }
    }

    public bool Save () {
      // Implement persistence logic.
      return true;
    }

    public bool Delete () {
      // Implement delete logic.
      return true;
    }
  }

  internal class NorthwindDataException: Exception {
    public NorthwindDataException(string msg) : base (msg) { }
  }
}
Imports System.Collections
Imports System.Configuration
Imports System.Data
Imports System.Data.SqlClient
Imports System.Web.UI
Imports System.Web.UI.WebControls

Namespace Samples.AspNet.VB

' EmployeeLogic is a stateless business object that encapsulates
' the operations one can perform on a NorthwindEmployee object.
'
Public Class EmployeeLogic

   ' Returns a collection of NorthwindEmployee objects.
   Public Shared Function GetAllEmployees() As ICollection
      Dim al As New ArrayList()

      Dim cts As ConnectionStringSettings = ConfigurationManager.ConnectionStrings("NorthwindConnection")

      Dim sds As New SqlDataSource(cts.ConnectionString, "SELECT EmployeeID FROM Employees")

      Try
         Dim IDs As IEnumerable = sds.Select(DataSourceSelectArguments.Empty)

         ' Iterate through the Enumeration and create a
         ' NorthwindEmployee object for each ID.
         Dim enumerator As IEnumerator = IDs.GetEnumerator()
         While enumerator.MoveNext()
            ' The IEnumerable contains DataRowView objects.
            Dim row As DataRowView = CType(enumerator.Current,DataRowView)
            Dim id As String = row("EmployeeID").ToString()
            Dim nwe As New NorthwindEmployee(id)
            ' Add the NorthwindEmployee object to the collection.
            al.Add(nwe)
         End While
      Finally
         ' If anything strange happens, clean up.
         sds.Dispose()
      End Try

      Return al
   End Function 'GetAllEmployees

   ' To support basic filtering, the employees cannot
   ' be returned as an array of objects, rather as a
   ' DataSet of the raw data values.
   Public Shared Function GetAllEmployeesAsDataSet() As DataSet
      Dim employees As ICollection = GetAllEmployees()

      Dim ds As New DataSet("Table")

      ' Create the schema of the DataTable.
      Dim dt As New DataTable()
      Dim dc As DataColumn
      dc = New DataColumn("FirstName", GetType(String))
      dt.Columns.Add(dc)
      dc = New DataColumn("LastName", GetType(String))
      dt.Columns.Add(dc)
      dc = New DataColumn("Title", GetType(String))
      dt.Columns.Add(dc)
      dc = New DataColumn("Courtesy", GetType(String))
      dt.Columns.Add(dc)
      dc = New DataColumn("Supervisor", GetType(Int32))
      dt.Columns.Add(dc)

      ' Add rows to the DataTable.
      Dim emplEnum As IEnumerator = employees.GetEnumerator()
      Dim row As DataRow
      Dim ne As NorthwindEmployee
      While emplEnum.MoveNext()
         ne = CType(emplEnum.Current, NorthwindEmployee)
         row = dt.NewRow()
         row("FirstName") = ne.FirstName
         row("LastName") = ne.LastName
         row("Title") = ne.Title
         row("Courtesy") = ne.Courtesy
         row("Supervisor") = ne.Supervisor
         dt.Rows.Add(row)
      End While
      ' Add the complete DataTable to the DataSet.
      ds.Tables.Add(dt)

      Return ds
   End Function 'GetAllEmployeesAsDataSet

   Public Shared Function GetEmployee(anID As Object) As NorthwindEmployee
      If anID.Equals("-1") OrElse anID.Equals(DBNull.Value) Then
         Return New NorthwindEmployee()
      Else
         Return New NorthwindEmployee(anID)
      End If
   End Function 'GetEmployee


   Public Shared Sub UpdateEmployeeInfo(ne As NorthwindEmployee)
      Dim retval As Boolean = ne.Save()
      If Not retval Then
         Throw New NorthwindDataException("UpdateEmployee failed.")
      End If
   End Sub

   Public Shared Sub DeleteEmployee(ne As NorthwindEmployee)
      Dim retval As Boolean = ne.Delete()
      If Not retval Then
         Throw New NorthwindDataException("DeleteEmployee failed.")
      End If
   End Sub
End Class


Public Class NorthwindEmployee


   Public Sub New()
      ID = DBNull.Value
      aLastName = ""
      aFirstName = ""
      aTitle = ""
      titleOfCourtesy = ""
      reportsTo = - 1
   End Sub


   Public Sub New(anID As Object)
      Me.ID = anID

      Dim cts As ConnectionStringSettings = ConfigurationManager.ConnectionStrings("NorthwindConnection")

      Dim conn As New SqlConnection(cts.ConnectionString)

      Dim sc As New SqlCommand(" SELECT FirstName,LastName,Title,TitleOfCourtesy,ReportsTo " & _
                               " FROM Employees " & _
                               " WHERE EmployeeID = @empId", conn)
      ' Add the employee ID parameter and set its value.
      sc.Parameters.Add(New SqlParameter("@empId", SqlDbType.Int)).Value = Int32.Parse(anID.ToString())
      Dim sdr As SqlDataReader = Nothing

      Try
         conn.Open()
         sdr = sc.ExecuteReader()

         ' Only loop once.
         If Not (sdr Is Nothing) AndAlso sdr.Read() Then
            ' The IEnumerable contains DataRowView objects.
            Me.aFirstName = sdr("FirstName").ToString()
            Me.aLastName = sdr("LastName").ToString()
            Me.aTitle = sdr("Title").ToString()
            Me.titleOfCourtesy = sdr("TitleOfCourtesy").ToString()
            If Not sdr.IsDBNull(4) Then
               Me.reportsTo = sdr.GetInt32(4)
            End If
         Else
            Throw New NorthwindDataException("Data not loaded for employee id.")
         End If
      Finally
         Try
            If Not (sdr Is Nothing) Then
               sdr.Close()
            End If
            conn.Close()
         Catch se As SqlException
            ' Log an event in the Application Event Log.
            Throw
         End Try
      End Try
   End Sub

   Private ID As Object
   Public ReadOnly Property EmpID() As String
      Get
         Return ID.ToString()
      End Get
   End Property

   Private aLastName As String
   Public Property LastName() As String
      Get
         Return aLastName
      End Get
      Set
         aLastName = value
      End Set
   End Property

   Private aFirstName As String
   Public Property FirstName() As String
      Get
         Return aFirstName
      End Get
      Set
         aFirstName = value
      End Set
   End Property

   Public ReadOnly Property FullName() As String
      Get
         Return FirstName & " " & LastName
      End Get
   End Property

   Private aTitle As String
   Public Property Title() As String
      Get
         Return aTitle
      End Get
      Set
         aTitle = value
      End Set
   End Property

   Private titleOfCourtesy As String
   Public Property Courtesy() As String
      Get
         Return titleOfCourtesy
      End Get
      Set
         titleOfCourtesy = value
      End Set
   End Property

   Private reportsTo As Integer
   Public Property Supervisor() As Integer
      Get
         Return reportsTo
      End Get
      Set
         reportsTo = value
      End Set
   End Property

   Public Function Save() As Boolean

      ' Implement persistence logic.
      Return True

   End Function 'Save


   Public Function Delete() As Boolean

      ' Implement delete logic.
      Return True

   End Function 'Delete
End Class


Friend Class NorthwindDataException
   Inherits Exception

   Public Sub New(msg As String)
      MyBase.New(msg)
   End Sub
End Class
End Namespace

Comentários

O ObjectDataSource controle dá suporte a uma política de expiração opcional baseada no SqlCacheDependency objeto para o cache de dados (o serviço deve ser configurado para o servidor de banco de dados).

O SQL Server dá suporte a dois mecanismos para invalidação de cache: sondagem e notificação. Cada mecanismo tem uma sintaxe diferente para o SqlCacheDependency objeto .

O ObjectDataSource dá suporte apenas à sondagem. A SqlCacheDependency cadeia de caracteres é usada para criar um SqlDependency objeto que é passado para o DbCommand construtor antes que o Select método seja executado. A SqlCacheDependency cadeia de caracteres identifica bancos de dados e tabelas de acordo com o mesmo formato usado pela @ Page diretiva , em que a primeira parte da cadeia de caracteres é uma cadeia de conexão para um banco de dados do SQL Server, seguida por um delimitador de dois-pontos e, por fim, o nome da tabela de banco de dados (por exemplo, "connectionstring1:table1"). Se a SqlCacheDependency propriedade depender de mais de uma tabela, os pares de cadeia de conexão e nome da tabela serão separados por ponto e vírgula (por exemplo, "connectionstring1:table1";connectionstring2:table2").

Para dar suporte à notificação, você deve escrever a lógica de cache na implementação de sua SelectMethod propriedade e manipular a construção do SqlCacheDependency objeto em seu código.

Aplica-se a

Confira também