/// <summary>
        /// 当用户点击分页编号按钮时引发此事件。
        /// </summary>
        /// <param name="sender">分页按钮对象。</param>
        /// <param name="e">默认的时间数据。</param>
        private void PageNumberButton_Click(object sender, EventArgs e)
        {
            PageNumberButton btn = sender as PageNumberButton;

            //this.PageIndex = btn.PageNumber - 1;
            this.DoPageIndexChanging(btn.PageNumber - 1);
        }
        /// <summary>
        /// 更新显示的分页按钮。
        /// </summary>
        /// <param name="ABS">是否强制更新分页页码按钮。</param>
        private void RefreshPageNumberButtons(bool ABS)
        {
            int startPageIndex = this.PageIndex - this.PageGroupSize / 2;

            if (startPageIndex + this.PageGroupSize > this.PagesCount - 1)
            {
                startPageIndex = this.PagesCount - this.PageGroupSize;
            }
            if (startPageIndex < 0)
            {
                startPageIndex = 0;
            }
            this.FirstPageButton.Enabled = this.PreviousPageGroupButton.Enabled = this.PreviousPageButton.Enabled = (this.PageIndex > 0);
            this.LastPageButton.Enabled  = this.NextPageGroupButton.Enabled = this.NextPageButton.Enabled = (this.PageIndex < this.PagesCount - 1);

            bool ReCreatePageNumberButtons = true; //指示是否需要重新设置分页编号按钮。

            #region 判断是否需要重新设置分页编号按钮。
            if (!ABS && this._ShowPageNumberButtons)
            {
                #region 找到当前显示的最大分页编号和最小分页编号。
                int  curSPI = 0; //最小分页编号。
                int  curMPI = 0; //最大分页编号。
                bool first  = true;
                foreach (var tmp in this.Items)
                {
                    if (tmp is PageNumberButton || tmp is CurrentPageNumberButton)
                    {
                        int k;
                        if (tmp is PageNumberButton)
                        {
                            k = ((PageNumberButton)tmp).PageNumber - 1;
                        }
                        else// if (tmp is CurrentPageNumberButton)
                        {
                            k = ((CurrentPageNumberButton)tmp).PageNumber - 1;
                        }
                        if (first)
                        {
                            first  = false;
                            curSPI = k;
                            curMPI = k;
                        }
                        else
                        {
                            if (k < curSPI)
                            {
                                curSPI = k;
                            }
                            else if (k > curMPI)
                            {
                                curMPI = k;
                            }
                        }
                    }
                }
                #endregion

                if (!first) //如果 first 发生反转则执行重新生成分页编号按钮的判断。
                {
                    int jj = startPageIndex + this.PageGroupSize - 1;
                    if (jj >= this.PagesCount)
                    {
                        jj = this.PagesCount - 1;
                    }
                    if (curSPI == startPageIndex && curMPI == jj)
                    {
                        ReCreatePageNumberButtons = false;
                    }
                }
            }
            #endregion

            #region 重新生成页码按钮。
            if (!this._ShowPageNumberButtons || ReCreatePageNumberButtons) //当不显示分页编码按钮或需要重新创建分页编码按钮时,需要清除已存在的分页编码按钮。
            {
                this.ClearPageNumberButton();
            }

            if (this._ShowPageNumberButtons && ReCreatePageNumberButtons)
            {
                int insertIndex = this.Items.IndexOf(this.NextPageButton); //计算记录插入位置。

                for (int i = startPageIndex; i < startPageIndex + this.PageGroupSize && i < this.PagesCount; i++)
                {
                    if (i == this.PageIndex) //当前分页。
                    {
                        CurrentPageNumberButton btn = new CurrentPageNumberButton();
                        btn.ForeColor   = this.CurrentPageButtonForColor;
                        btn.BackColor   = this.CurrentPageButtonBackColor;
                        btn.Font        = this.CurrentPageButtonFont;
                        btn.Text        = (i + 1).ToString();
                        btn.ToolTipText = string.Format("第 {0} 页", i + 1);
                        this.Items.Insert(insertIndex++, btn);
                    }
                    else
                    {
                        PageNumberButton btn = new PageNumberButton(i + 1);
                        btn.ToolTipText = string.Format("第 {0} 页", i + 1);
                        btn.Click      += new EventHandler(this.PageNumberButton_Click);
                        this.Items.Insert(insertIndex++, btn);
                    }
                }
            }
            #endregion

            int crc = this.PageSize;                                       //当前页记录总数
            if (this.RecordsCount <= this.PageSize * (this.PageIndex + 1)) //如果尾页则需要统计记录实际数量。
            {
                crc = this.RecordsCount - this.PageSize * this.PageIndex;
            }
            if (crc < 0)
            {
                crc = 0;
            }
            this._PageSizeLabel.Text     = string.Format(this.PageSizeLabelFormatString, crc);
            this._RecordsCountLabel.Text = string.Format(this.RecordsCountLabelFormatString, this.RecordsCount);
            this._PageIndexLabel.Text    = string.Format(this.PageIndexLabelFormatString, this.PageIndex + 1);
            this._PagesCountLabel.Text   = string.Format(this.PagesCountLabelFormatString, this.PagesCount);

            #region 调整当前分页说明标签的位置,以满足按钮项目的布局合理性。
            if (this.ShowPageIndexLabel && !this.ShowPageNumberButtons)
            {
                this.Items.Remove(this._PageIndexLabel);
                int insertIndex = this.Items.IndexOf(this._NextPageButton);
                if (insertIndex != -1)
                {
                    this.Items.Insert(insertIndex, this._PageIndexLabel);
                }
            }
            else
            {
                this.Items.Remove(this._PageIndexLabel);
                int insertIndex = this.Items.IndexOf(this._PagesCountLabel);
                if (insertIndex != -1)
                {
                    this.Items.Insert(insertIndex, this._PageIndexLabel);
                }
            }
            #endregion

            this.FixItemsPosition();
        }