yaosansi's Blog

         使用DataGrid时自带的分页实现起来虽然比较方便，但是效率不高，每次都需要读取所有页（整个记录集），而加载的只是其中一页，造成了资源的浪费，记录多又会使效率变得很低。下面通过DataGrid的自定义分页功能来减少资源使用和提高效率。

         实现的关键是设置AllowCustomPaging属性位True,并把VirtualItemCount属性设置位总的记录数，给分页提供依据，前台的主要代码如下：

<form id="Form1" method="post" runat="server">

                            <TABLE id="Table1" style="FONT-SIZE: 9pt" cellSpacing="1" cellPadding="1" width="450" align="center"

                                     border="1">

                                     <TR>

                                               <TD>

                                                        <asp:datagrid id="DataGrid1" runat="server" Width="100％" AllowPaging="True" AllowCustomPaging="True">

                                                                 <PagerStyle Font-Size="9pt" Mode="NumericPages"></PagerStyle>

                                                        </asp:datagrid></TD>

                                     </TR>

                            </TABLE>

                   </form>

这里使用的数据源还是假设为Northwind的Customers表。

下面是访问单页的存储过程，实现方式很多，不过这个是最普通的，

Create PROCEDURE [GetCustomersDataPage]

         @PageIndex INT,

         @PageSize  INT,

         @RecordCount INT OUT,

         @PageCount INT OUT

AS

Select @RecordCount = COUNT(*)  FROM   Customers

SET @PageCount = CEILING(@RecordCount * 1.0 / @PageSize)

DECLARE @SQLSTR NVARCHAR(1000)

IF @PageIndex = 0 or @PageCount <= 1

         SET @SQLSTR =N'Select TOP '+STR( @PageSize )+

'  CustomerID, CompanyName,Address,Phone  FROM   Customers orDER BY CustomerID DESC'

ELSE IF     @PageIndex = @PageCount - 1            

         SET @SQLSTR =N' Select * FROM ( Select TOP '+STR( @RecordCount - @PageSize * @PageIndex )+

'  CustomerID, CompanyName,Address,Phone  FROM   Customers orDER BY CustomerID ASC ) TempTable  ORDER BY CustomerID DESC'

ELSE         

        SET @SQLSTR =N' Select TOP  '+STR( @PageSize )+' * FROM ( Select TOP '+STR( @RecordCount - @PageSize * @PageIndex )+

'  CustomerID, CompanyName,Address,Phone  FROM   Customers orDER BY CustomerID ASC ) TempTable orDER BY CustomerID DESC'

EXEC (@SQLSTR)

GO

获取记录数和页数都采用存储过程的输出参数。

获取数据源，这里返回一个DataSet。

先定义了连个数据成员，

private int pageCount;//页数

private int recordCount;//记录数

//获取单页数据

private static DataSet GetCustomersData(int pageIndex,int pageSize,ref int recordCount,ref int pageCount)

{

     string connString = ConfigurationSettings.AppSettings["ConnString"];

     SqlConnection conn = new SqlConnection(connString);

     SqlCommand comm = new SqlCommand("GetCustomersDataPage",conn);

     comm.Parameters.Add(new SqlParameter("@PageIndex",SqlDbType.Int));

     comm.Parameters[0].Value = pageIndex;

     comm.Parameters.Add(new SqlParameter("@PageSize",SqlDbType.Int));

     comm.Parameters[1].Value = pageSize;

     comm.Parameters.Add(new SqlParameter("@RecordCount",SqlDbType.Int));

     comm.Parameters[2].Direction = ParameterDirection.Output;

     comm.Parameters.Add(new SqlParameter("@PageCount",SqlDbType.Int));

     comm.Parameters[3].Direction = ParameterDirection.Output;

     comm.CommandType = CommandType.StoredProcedure;

     SqlDataAdapter dataAdapter = new SqlDataAdapter(comm);

     DataSet ds = new DataSet();

     dataAdapter.Fill(ds);

     recordCount = (int)comm.Parameters[2].Value;

     pageCount = (int)comm.Parameters[3].Value;

     return ds;

}

//绑定数据到DataGrid，同时刷新数据总记录数

private void DataGridDataBind()

{

     DataSet ds = GetCustomersData(PageIndex,PageSize,ref recordCount,ref pageCount);

     this.DataGrid1.VirtualItemCount = RecordCount;

     this.DataGrid1.DataSource = ds;

     this.DataGrid1.DataBind();

}

下面是分页的几个变量属性

public int PageCount

{

     get{return this.DataGrid1.PageCount;}

}

public int PageSize

{

     get{return this.DataGrid1.PageSize;}

}

public int PageIndex

{

     get{return this.DataGrid1.CurrentPageIndex;}

     set{this.DataGrid1.CurrentPageIndex = value;}

}

public int RecordCount

{

     get{return recordCount;}

}

注册DataGrid分页事件

//分页事件处理

private void DataGrid1_PageIndexChanged(object source, System.Web.UI.WebControls.DataGridPageChangedEventArgs e)

{

     DataGrid dg = (DataGrid)source;

     dg.CurrentPageIndex = e.NewPageIndex;

     DataGridDataBind();

}

最好判断当前页面是否是第一次加载，防止重复加载两次数据，

private void Page_Load(object sender, System.EventArgs e)

{

     if(!Page.IsPostBack)

     {

         DataGridDataBind();

     }

}

显示界面如下：

这个例子中没有显示分页的一些参数，我们可以进一步对其进行改进。