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 >