后台指定GridView的ItemTemplate

     其实工作之后做的第一个项目就不提倡使用服务器控件了，不过最近在维护公司的一个老系统，其中用到了GridView。

     新需求是在GridView表头上添加排序功能。原有效果是不带分页的GridView，超出高度会显示滚动条，于是我就粗略判断此处数据量不大。采用的实现方法是直接取当前GridView的HTML作为XML数据源（IE下innerHtml获得的HTML字符串中属性值的双引号是没有的，所以此字符串不会识别成标准的XML，只有使用网上的自动补上双引号的方法才可作为XML使用），然后使用熟悉的XSLT进行排序。结果发布后没多久客服告诉我们用户反映排序很慢，问了测试人员才知道实际中有2000多条数据的情况……

     这个系统的Sping.NET+NHibernate架构我还是刚开始接触，加之系统中的业务相当复杂，在改新功能的时候一直都比较谨慎，一直保持着尽量少改动原有方法的原则。在知道了新的问题之后，我采取的实现方法是，使用AJAX发送排序请求，后台排序之后再绑定GridView然后获得GridView的HTML返回到前台，前台使用JS更新列表。

     其实页面中已经添加了GridView并且也绑定了数据，但是在实际测试的时候发现即使排序完成，IE状态栏的进度条却一直没有走完。当时判断是使用JS操作服务器控件GridView出现的问题，所以将前台的GridView删除了，而是在后台声明GridView并初始化、绑定。但是测试之后发现进度条没走完的情况依然存在，使用Fiddler监控发现每次排序完成都会请求一次csshover.htc文件，试着将查找引用csshover.htc文件的样式，发现正好是GridView的样式。于是移除此样式之后，进度条没走完的问题终于没有了。

     后台指定GridView的ItemTemplate用到的模板类如下：

public class GridViewTextTemplate : ITemplate

{

    private string templateTypeName;

    private string columnName;

    private string Id;



    public GridViewTextTemplate(string typeStr, string colname, string controlId)

    {

        templateTypeName = typeStr;

        columnName = colname;

        Id = controlId;

    }



    public void InstantiateIn(System.Web.UI.Control container)

    {

        switch (templateTypeName)

        {

            case "CheckBox":

                CheckBox checkBox = new CheckBox();

                checkBox.ID = Id;

                container.Controls.Add(checkBox);

                break;

            case "Label":

                Label label = new Label();

                label.ID = Id;

                label.DataBinding += new EventHandler(this.OnDataBinding);

                container.Controls.Add(label);

                break;

            case "HiddenField&LableInPanel":

                HiddenField hiddenField = new HiddenField();

                hiddenField.ID = "RecordID";

                hiddenField.DataBinding += new EventHandler(this.OnDataBinding);

                container.Controls.Add(hiddenField);



                Panel panel = new Panel();

                panel.CssClass = "panleStyle";

                Label labelInPanel = new Label();

                labelInPanel.ID = Id;

                labelInPanel.DataBinding += new EventHandler(this.OnDataBinding);

                panel.Controls.Add(labelInPanel);

                container.Controls.Add(panel);

                break;

            default:

                break;

        }

    }



    private void OnDataBinding(Object sender, EventArgs e)

    {

        GridViewRow row;

        if (columnName != "")

        {

            switch (templateTypeName)

            {

                case "Label":

                    Label labelInPanel = (Label)sender;

                    row = (GridViewRow)labelInPanel.NamingContainer;

                    labelInPanel.Text = Convert.ToDateTime(DataBinder.Eval(row.DataItem, columnName)).ToString("yyyy-MM-dd");

                    break;

                case "HiddenField&LableInPanel":

                    if (sender is HiddenField)

                    {

                        HiddenField hiddenField = (HiddenField)sender;

                        row = (GridViewRow)hiddenField.NamingContainer;

                        hiddenField.Value = DataBinder.Eval(row.DataItem, "ID").ToString();

                        break;

                    }

                    else if (sender is Label)

                    {

                        Label label = (Label)sender;

                        row = (GridViewRow)label.NamingContainer;

                        label.Text = DataBinder.Eval(row.DataItem, "RecordNo").ToString().Length > 18 ? DataBinder.Eval(row.DataItem, "RecordNo").ToString().Substring(0, 18) + "..." : DataBinder.Eval(row.DataItem, "RecordNo").ToString();

                    }

                    break;

                default:

                    break;

            }

        }

    }



}

使用：

    private GridView GetRecordGridView()

    {

        GridView grid_Record = new GridView();

        grid_Record.ID = "grid_Record";

        grid_Record.Width = 260;

        grid_Record.AutoGenerateColumns = false;

        grid_Record.DataKeyNames = new string[] { "Id" };

        grid_Record.CssClass = "listGridView";



        TemplateField col_chose = new TemplateField();

        col_chose.HeaderText = "选择";

        col_chose.ItemTemplate = new GridViewTextTemplate("CheckBox", "", "chkRecord");

        grid_Record.Columns.Add(col_chose);



        TemplateField col_recordID = new TemplateField();

        col_recordID.HeaderText = "单号";

        //col_recordID.ItemTemplate = new GridViewTextTemplate("HiddenField", "ID", "RecordID");

        col_recordID.ItemTemplate = new GridViewTextTemplate("HiddenField&LableInPanel", "RecordNo", "lblRecordNo");

        grid_Record.Columns.Add(col_recordID);



        TemplateField col_saveDate = new TemplateField();

        col_saveDate.HeaderText = "日期";

        col_saveDate.ItemTemplate = new GridViewTextTemplate("Label", "SaveDate", "lblSaveDate");

        grid_Record.Columns.Add(col_saveDate);



        return grid_Record;

    }

获取GridView的HTML的方法：

    public string RenderGridView(GridView grid)

    {

        System.Text.StringBuilder sb = new System.Text.StringBuilder();

        System.IO.StringWriter sw = new System.IO.StringWriter(sb);

        HtmlTextWriter htw = new HtmlTextWriter(sw);

        grid.RenderControl(htw);



        return sb.ToString();

    }