c# - 没有数据源控制的高效 Gridview 分页问题

Question

我正在尝试在不使用数据源控件的情况下使用 gridview 进行高效分页。高效是指我只检索我打算显示的记录。

我正在尝试使用 PagerTemplate 来构建我的寻呼机功能。

简而言之，问题是如果我只绑定(bind)我打算在当前页面上显示的记录，则 gridview 不会呈现其分页模板，因此我无法获得分页控件。

这几乎就好像我必须绑定(bind)比我打算在给定页面上显示的记录更多的记录，这不是我想做的事情。

Answer 1

您需要创建一个继承自 GridView 的自定义 gridview 控件。没有 DataSourceControl，gridview 不知道可能绑定(bind)到控件的记录总数。如果绑定(bind) 100 条记录中的 10 条并将 PageSize 属性设置为 10，则 gridview 仅知道有 10 条记录将小于或等于 PageSize，并且分页控件将不会显示。为了让您的 gridview 显示寻呼机，它必须知道可能被检索的记录总数。通过继承gridview，重写InitializePager方法，我们可以拦截pagedDataSource，修改AllowCustomPaging和VirtualCount方法。

这是我创造的

using System;
using System.Collections.Generic;
using System.Text;
using System.Web.UI.WebControls;
using System.ComponentModel;

namespace cly.Web.CustomControls
{
    public class clyGridView : GridView
    {
        private const string _virtualCountItem = "bg_vitemCount";
        private const string _sortColumn = "bg_sortColumn";
        private const string _sortDirection = "bg_sortDirection";
        private const string _currentPageIndex = "bg_pageIndex";

        public clyGridView ()
            : base()
        {
        }

        #region Custom Properties
        [Browsable(true), Category("NewDynamic")]
        [Description("Set the virtual item count for this grid")]
        public int VirtualItemCount
        {
            get
            {
                if (ViewState[_virtualCountItem] == null)
                    ViewState[_virtualCountItem] = -1;
                return Convert.ToInt32(ViewState[_virtualCountItem]);
            }
            set
            {
                ViewState[_virtualCountItem] = value;
            }
        }        

        public string GridViewSortColumn
        {
            get
            {
                if (ViewState[_sortColumn] == null)
                    ViewState[_sortColumn] = string.Empty;
                return ViewState[_sortColumn].ToString();
            }
            set
            {
                if (ViewState[_sortColumn] == null || !ViewState[_sortColumn].Equals(value))
                    GridViewSortDirection = SortDirection.Ascending;
                ViewState[_sortColumn] = value;
            }
        }

        public SortDirection GridViewSortDirection
        {
            get
            {
                if (ViewState[_sortDirection] == null)
                    ViewState[_sortDirection] = SortDirection.Ascending;
                return (SortDirection)ViewState[_sortDirection];
            }
            set
            {
                ViewState[_sortDirection] = value;
            }
        }

        private int CurrentPageIndex
        {
            get
            {
                if (ViewState[_currentPageIndex] == null)
                    ViewState[_currentPageIndex] = 0;
                return Convert.ToInt32(ViewState[_currentPageIndex]);
            }
            set
            {
                ViewState[_currentPageIndex] = value;
            }
        }

        private bool CustomPaging
        {
            get { return (VirtualItemCount != -1); }
        }
        #endregion

        #region Overriding the parent methods
        public override object DataSource
        {
            get
            {
                return base.DataSource;
            }
            set
            {
                base.DataSource = value;
                // store the page index so we don't lose it in the databind event
                CurrentPageIndex = PageIndex;
            }
        }

        protected override void OnSorting(GridViewSortEventArgs e)
        {            
            //Store the direction to find out if next sort should be asc or desc
            SortDirection direction = SortDirection.Ascending;
            if (ViewState[_sortColumn] != null &&  (SortDirection)ViewState[_sortDirection] == SortDirection.Ascending)
            {
                direction = SortDirection.Descending;
            }
            GridViewSortDirection = direction;
            GridViewSortColumn = e.SortExpression;
            base.OnSorting(e);
        }

        protected override void InitializePager(GridViewRow row, int columnSpan, PagedDataSource pagedDataSource)
        {
            // This method is called to initialise the pager on the grid. We intercepted this and override
            // the values of pagedDataSource to achieve the custom paging using the default pager supplied
            if (CustomPaging)
            {
                pagedDataSource.VirtualCount = VirtualItemCount;
                pagedDataSource.CurrentPageIndex = CurrentPageIndex;
            }
            base.InitializePager(row, columnSpan, pagedDataSource);
        }

        protected override object SaveViewState()
        {
            //object[] state = new object[3];
            //state[0] = base.SaveViewState();
            //state[1] = this.dirtyRows;
            //state[2] = this.newRows;
            //return state;

            return base.SaveViewState();
        }

        protected override void LoadViewState(object savedState)
        {

            //object[] state = null;

            //if (savedState != null)
            //{
            //    state = (object[])savedState;
            //    base.LoadViewState(state[0]);
            //    this.dirtyRows = (List<int>)state[1];
            //    this.newRows = (List<int>)state[2];
            //}

            base.LoadViewState(savedState);
        }
        #endregion

        public override string[] DataKeyNames
        {
            get
            {
                return base.DataKeyNames;
            }
            set
            {
                base.DataKeyNames = value;
            }
        }

        public override DataKeyArray DataKeys
        {
            get
            {
                return base.DataKeys;
            }
        }

        public override DataKey SelectedDataKey
        {
            get
            {
                return base.SelectedDataKey;
            }
        }
    }
}

然后当你绑定(bind)数据时:

gv.DataSource = yourListOrWhatever
gv.VirtualItemCount = numOfTotalRecords;
gv.DataBind();