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ObjectDataSource.CacheDuration Property

Note: This property is new in the .NET Framework version 2.0.

Gets or sets the length of time, in seconds, that the data source control caches data that is retrieved by the SelectMethod method.

Namespace: System.Web.UI.WebControls
Assembly: System.Web (in system.web.dll)

public virtual int CacheDuration { get; set; }
/** @property */
public int get_CacheDuration ()

/** @property */
public void set_CacheDuration (int value)

public function get CacheDuration () : int

public function set CacheDuration (value : int)

Property Value

The number of seconds that the ObjectDataSource caches the results of a SelectMethod property invocation. The default is 0. The value cannot be negative.

The ObjectDataSource control supports data caching. While data is cached, calls to the Select method retrieve data from the cache rather than from the business object that the ObjectDataSource works with. When the cache expires, the Select method retrieves data from the business object, and then caches the data again.

The ObjectDataSource control automatically caches data when the EnableCaching property is set to true and the CacheDuration property is set to a value greater than 0, which indicates the number of seconds that the cache stores data before the cache entry is discarded. A value of 0 indicates an infinitely long cache.

The cache is regulated by a combination of the duration and the CacheExpirationPolicy setting. If the CacheExpirationPolicy property is set to the Absolute value, the ObjectDataSource caches data on the first call to the Select method and holds it in memory for, at most, the amount of time that is specified by the CacheDuration property. The data might be released before the duration time, if the memory is needed. The cache is then refreshed during the next call to the Select method. If the CacheExpirationPolicy property is set to Sliding value, the data source control caches data on the first call to the Select method, but resets the time window for which it holds the cache on each subsequent call to the Select method. The cache expires, if there is no activity for a time that is equal to the CacheDuration property since the last call to the Select method.

This section contains two code examples. The first code example demonstrates how an ObjectDataSource object supports caching. The second code example demonstrates how to implement a wrapper method that returns a DataSet object to enable caching with an ObjectDataSource object.

The following code example demonstrates how an ObjectDataSource control supports caching. To enable caching, you must implement the method that retrieves data, which is identified by the SelectMethod property, to return the data as a DataSet object. In this example, the EnableCaching property is set to true, and the CacheDuration and CacheExpirationPolicy properties are set. The ObjectDataSource caches data that is returned by the SelectMethod property for 30 seconds.

<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.CS" Assembly="Samples.AspNet.CS" %>
<%@ Page language="c#" %>
<html>
  <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="30"
          cacheexpirationpolicy="Absolute" />

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

<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.jsl" Assembly="Samples.AspNet.jsl" %>
<%@ Page Language="VJ#" %>
<html>
  <head>
    <title>ObjectDataSource - VJ# 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.jsl.EmployeeLogic"
          selectmethod="GetAllEmployeesAsDataSet"
          enablecaching="True"
          cacheduration="30"
          cacheexpirationpolicy="Absolute" />

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

The following code example demonstrates how to implement a wrapper method that returns a DataSet object to enable caching with an ObjectDataSource control. In the base implementation of the EmployeeLogic class, the GetAllEmployees method returns an ArrayList object. Instead of refactoring the object completely to work with the ObjectDataSource on a Web Forms page, a wrapper method named GetAllEmployeesAsDataSet is added that returns a set of NorthwindEmployee data as a DataSet.

This code example is part of a larger example provided for the ObjectDataSource class.

//
// 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;
}

//
// 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() throws NorthwindDataException
{
    ICollection employees = GetAllEmployees();

    DataSet ds = new DataSet("Table");
    // Create the schema of the DataTable.
    DataTable dt = new DataTable();
    DataColumn dc;
    dc = new DataColumn("FirstName", String.class.ToType());
    dt.get_Columns().Add(dc);
    dc = new DataColumn("LastName", String.class.ToType());
    dt.get_Columns().Add(dc);
    dc = new DataColumn("Title", String.class.ToType());
    dt.get_Columns().Add(dc);
    dc = new DataColumn("Courtesy", String.class.ToType());
    dt.get_Columns().Add(dc);
    dc = new DataColumn("Supervisor", Int32.class.ToType());
    dt.get_Columns().Add(dc);
    // Add rows to the DataTable.
    IEnumerator emplEnum = employees.GetEnumerator();
    DataRow row;
    NorthwindEmployee ne;
    while (emplEnum.MoveNext()) {
        ne = (NorthwindEmployee)emplEnum.get_Current();
        row = dt.NewRow();
        row.set_Item("FirstName", ne.get_FirstName());
        row.set_Item("LastName", ne.get_LastName());
        row.set_Item("Title", ne.get_Title());
        row.set_Item("Courtesy", ne.get_Courtesy());
        row.set_Item("Supervisor", (Int32)ne.get_Supervisor());
        dt.get_Rows().Add(row);
    }
    // Add the complete DataTable to the DataSet.
    ds.get_Tables().Add(dt);

    return ds;
} //GetAllEmployeesAsDataSet


Windows 98, Windows 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0

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