DataSet 的Cache功能

在内存中保存一个DataView

public DataView GetProducts()
{
    DataSet dstProducts;
    SqlConnection conNorthwind;
    SqlDataAdapter dadProducts;
    DataView dvwProducts = Cache["Products"] as DataView;
    if (dvwProducts == null)
    {
        dstProducts = new DataSet();
        conNorthwind = new SqlConnection( @"Server=localhost;Integrated Security=SSPI;Database=Northwind" );
        dadProducts = new SqlDataAdapter( "Select * from Products", conNorthwind );
        dadProducts.Fill( dstProducts, "Products" );
        dvwProducts = dstProducts.Tables["Products"].DefaultView;
        Cache["Products"] = dvwProducts;
    }
    return dvwProducts;
 } 

Cache一个DataSet
DataSet中有两表,如果不用可以Cache.Remove["Products"]去除

dstStore = (DataSet)Cache["Store"];
    //Cache.Remove("Products");
     
    if ( dstStore == null ) {
        dstStore = new DataSet();
        conNorthwind = new SqlConnection(  @"Server=localhost;Integrated Security=SSPI;Database=Northwind" );
        dadNorthwind = new SqlDataAdapter( "Select CategoryID, CategoryName From Categories", conNorthwind );
        conNorthwind.Open();
        dadNorthwind.Fill( dstStore, "Categories" );
        dadNorthwind.SelectCommand = new SqlCommand( "Select * From Products", conNorthwind );
        dadNorthwind.Fill( dstStore, "Products" );
        conNorthwind.Close();
        //DataSet dstStore = (DataSet)Cache["Store"];
    }

在内存中找到你所要的数据

DataSet dstEmployees;
    SqlConnection conNorthwind;
    SqlDataAdapter dadEmployees;
    DataView dvwEmployees;
    Object[] arrValues = new Object[2];
    int intEmployeeIndex;

    //Get cached DataView
      
    dvwEmployees = (DataView)Cache["Employees"];
    if (dvwEmployees == null)
    {
        dstEmployees = new DataSet();
        conNorthwind = new SqlConnection( @"Server=localhost;Integrated Security=SSPI;Database=Northwind" );
        dadEmployees = new SqlDataAdapter( "Select * From Employees", conNorthwind );
        dadEmployees.Fill( dstEmployees, "Employees" );
        dvwEmployees = dstEmployees.Tables["Employees"].DefaultView;
        dvwEmployees.Sort = "LastName, FirstName";
        Cache["Employees"] = dvwEmployees;
    }

    //Find the employee
    arrValues[0] = txtLastName.Text;
    arrValues[1] = txtFirstName.Text;
    if (dvwEmployees == null)
        intEmployeeIndex=-1;
    else
        intEmployeeIndex = dvwEmployees.Find( arrValues );
    if (intEmployeeIndex > -1 ) 
    {
        lblName.Text = txtLastName.Text + ", " + txtFirstName.Text;
        lblPhone.Text = dvwEmployees[ intEmployeeIndex ].Row[ "HomePhone" ].ToString();
        lblNotes.Text = dvwEmployees[ intEmployeeIndex ].Row[ "Notes" ].ToString();
    }
    else
        lblError.Text = "Employee Not Found!";

以下是源程序

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

<script runat=server>
void Button_Click(Object sender , EventArgs e) 
{
    DataSet dstEmployees;
    SqlConnection conNorthwind;
    SqlDataAdapter dadEmployees;
    DataView dvwEmployees;
    Object[] arrValues = new Object[2];
    int intEmployeeIndex;

    //Get cached DataView
      
    dvwEmployees = (DataView)Cache["Employees"];
    if (dvwEmployees == null)
    {
        dstEmployees = new DataSet();
        conNorthwind = new SqlConnection( @"Server=localhost;Integrated Security=SSPI;Database=Northwind" );
        dadEmployees = new SqlDataAdapter( "Select * From Employees", conNorthwind );
        dadEmployees.Fill( dstEmployees, "Employees" );
        dvwEmployees = dstEmployees.Tables["Employees"].DefaultView;
        dvwEmployees.Sort = "LastName, FirstName";
        Cache["Employees"] = dvwEmployees;
    }

    //Find the employee
    arrValues[0] = txtLastName.Text;
    arrValues[1] = txtFirstName.Text;
    if (dvwEmployees == null)
        intEmployeeIndex=-1;
    else
        intEmployeeIndex = dvwEmployees.Find( arrValues );
    if (intEmployeeIndex > -1 ) 
    {
        lblName.Text = txtLastName.Text + ", " + txtFirstName.Text;
        lblPhone.Text = dvwEmployees[ intEmployeeIndex ].Row[ "HomePhone" ].ToString();
        lblNotes.Text = dvwEmployees[ intEmployeeIndex ].Row[ "Notes" ].ToString();
    }
    else
        lblError.Text = "Employee Not Found!";
 }

</Script>

<html>
<head><title>CacheEmployees.aspx</title></head>
<body>

<h2>Employee Directory</h2>

<form Runat="Server">
<b>First Name:</b>
<asp:TextBox
  ID="txtFirstName"
  Runat="Server" />
<p>
<b>Last Name:</b>
<asp:TextBox
  ID="txtLastName"
  Runat="Server" />
<asp:Button
  Text="Find!"
  OnClick="Button_Click"
  Runat="Server" />
<hr>
<asp:Label
  ID="lblError"
  ForeColor="Red"
  EnableViewState="False"
  Runat="Server" />
<asp:Label
  ID="lblName"
  EnableViewState="False"
  Runat="Server" />
<p>
<asp:Label
  ID="lblPhone"
  EnableViewState="False"
  Runat="Server" />
<p>
<asp:Label
  ID="lblNotes"
  EnableViewState="False"
  Runat="Server" />
</form>

</body>
</html>