大数量查询分页显示 微软的解决办法

核心提示：微软的解决办法using System; using System.Data; using System.Data.SqlClient; using System.Drawing; using System.Windows.Forms; public class PagingSample: Form { // Form

微软的解决办法
using System;
using System.Data;
using System.Data.SqlClient;
using System.Drawing;
using System.Windows.Forms;

public class PagingSample: Form
{
// Form controls.
Button PRevBtn = new Button();
Button nextBtn = new Button();

static DataGrid myGrid = new DataGrid();
static Label pageLbl = new Label();

// Paging variables.
static int pageSize = 10; // Size of viewed page.
static int totalPages = 0; // Total pages.
static int currentPage = 0; // Current page.
static string firstVisibleCustomer = ""; // First customer on page to determine location for move previous.
static string lastVisibleCustomer = ""; // Last customer on page to determine location for move next.

// DataSet to bind to DataGrid.
static DataTable custTable;

// Initialize connection to database and DataAdapter.
static SqlConnection nwindConn = new SqlConnection("Data Source=localhost;Integrated Security=SSPI;Initial Catalog=northwind");
static SqlDataAdapter custDA = new SqlDataAdapter("", nwindConn);
static SqlCommand selCmd = custDA.SelectCommand;

public static void GetData(string direction)
{
// Create SQL statement to return a page of records.
selCmd.Parameters.Clear();

switch (direction)
{
case "Next":
selCmd.CommandText = "SELECT TOP " + pageSize + " CustomerID, CompanyName FROM Customers " +
"WHERE CustomerID > @CustomerId ORDER BY CustomerID";
selCmd.Parameters.Add("@CustomerId", SqlDbType.VarChar, 5).Value = lastVisibleCustomer;
break;
case "Previous":
selCmd.CommandText = "SELECT TOP " + pageSize + " CustomerID, CompanyName FROM Customers " +
"WHERE CustomerID < @CustomerId ORDER BY CustomerID DESC";
selCmd.Parameters.Add("@CustomerId", SqlDbType.VarChar, 5).Value = firstVisibleCustomer;
break;
default:
selCmd.CommandText = "SELECT TOP " + pageSize + " CustomerID, CompanyName FROM Customers ORDER BY CustomerID";

// Determine total pages.
SqlCommand totCMD = new SqlCommand("SELECT Count(*) FROM Customers", nwindConn);
nwindConn.Open();
int totalRecords = (int)totCMD.ExecuteScalar();
nwindConn.Close();
totalPages = (int)Math.Ceiling((double)totalRecords / pageSize);

break;
}

// Fill a temporary table with query results.
DataTable tmpTable = new DataTable("Customers");
int recordsAffected = custDA.Fill(tmpTable);

// If table does not exist, create it.
if (custTable == null)
custTable = tmpTable.Clone();

// Refresh table if at least one record returned.
if (recordsAffected > 0)
{
switch (direction)
{
case "Next":
currentPage++;
break;
case "Previous":
currentPage--;
break;
default:
currentPage = 1;
break;
}

pageLbl.Text = "Page " + currentPage + " of " + totalPages;

// Clear rows and add new results.
custTable.Rows.Clear();

foreach (DataRow myRow in tmpTable.Rows)
custTable.ImportRow(myRow);

// Preserve first and last primary key values.
DataRow[] ordRows = custTable.Select("", "CustomerID ASC");
firstVisibleCustomer = ordRows[0][0].ToString();
lastVisibleCustomer = ordRows[custTable.Rows.Count - 1][0].ToString();
}
}

public PagingSample()
{
// Initialize controls and add to form.
this.ClientSize = new Size(360, 274);
this.Text = "NorthWind Data";

myGrid.Location = new Point(10,10);
myGrid.Size = new Size(340, 220);
myGrid.AllowSorting = true;
myGrid.CaptionText = "NorthWind Customers";
myGrid.ReadOnly = true;
myGrid.AllowNavigation = false;
myGrid.PreferredColumnWidth = 150;

prevBtn.Text = "<<";
prevBtn.Size = new Size(48, 24);
prevBtn.Location = new Point(92, 240);
prevBtn.Click += new EventHandler(Prev_OnClick);

nextBtn.Text = ">>";
nextBtn.Size = new Size(48, 24);
nextBtn.Location = new Point(160, 240);

pageLbl.Text = "No Records Returned.";
pageLbl.Size = new Size(130, 16);
pageLbl.Location = new Point(218, 244);

this.Controls.Add(myGrid);
this.Controls.Add(prevBtn);
this.Controls.Add(nextBtn);
this.Controls.Add(pageLbl);
nextBtn.Click += new EventHandler(Next_OnClick);

// Populate DataSet with first page of records and bind to grid.
GetData("Default");
DataView custDV = new DataView(custTable, "", "CustomerID", DataViewRowState.CurrentRows);
myGrid.SetDataBinding(custDV, "");
}

public static void Prev_OnClick(object sender, EventArgs args)
{
GetData("Previous");
}

public static void Next_OnClick(object sender, EventArgs args)
{
GetData("Next");
}
}

public class Sample
{
static void Main()
{
application.Run(new PagingSample());
}
}