GridView当数据源为空时如何实现显示表头

来源：互联网发布：the eric python ide 编辑：程序博客网时间：2024/04/30 07:44

问题:asp.net 2.0 中引入的GridView控件当其数据源为空时(GridView.DataSource=null)不能显示
出表头.

解决:

方法一:采用其EmptyTemplate来实现,模版中写一个静态的table;
缺点: 麻烦,每个GridVIew都需要设置一下.

方法二: 若数据源为DataTable,则当无数据时,始终返回一个空行的DataTable;
若数据源是集合类(ArrayList,List等),无数据时,生成一个空的实体,加入到集合类中.
缺点: 还是麻烦.

方法三:
也是要给大家介绍的方法: 扩展GridView来实现.继承GridVie,重写Render方法,当其数据源为空时做一下处理,直接看代码吧:

///

/// GridView 扩展控件
///

     public class GridView : System.Web.UI.WebControls.GridView
     {
         private bool _enableEmptyContentRender = true ;
        ///

/// 是否数据为空时显示标题行
///

         public bool EnableEmptyContentRender
         {
             set { _enableEmptyContentRender = value; }
             get { return _enableEmptyContentRender; }
         }

         private string _EmptyDataCellCssClass ;
        ///

/// 为空时信息单元格样式类
///

         public string EmptyDataCellCssClass
         {
             set { _EmptyDataCellCssClass = value ; }
             get { return _EmptyDataCellCssClass ; }
         }

        ///

/// 为空时输出内容
///

        ///
         protected virtual void RenderEmptyContent(HtmlTextWriter writer)
         {
             Table t = new Table(); //create a table
             t.CssClass = this.CssClass; //copy all property
             t.GridLines = this.GridLines;
             t.BorderStyle = this.BorderStyle;
             t.BorderWidth = this.BorderWidth;
             t.CellPadding = this.CellPadding;
             t.CellSpacing = this.CellSpacing;

             t.HorizontalAlign = this.HorizontalAlign;

             t.Width = this.Width;

             t.CopyBaseAttributes(this);

             TableRow row = new TableRow();
             t.Rows.Add(row);

             foreach (DataControlField f in this.Columns) //generate table header
             {
                 TableCell cell = new TableCell();

                 cell.Text = f.HeaderText;

                 cell.CssClass = "TdHeaderStyle1"; //这里把表头样式写死了

                 row.Cells.Add(cell);
             }

             TableRow row2 = new TableRow();
             t.Rows.Add(row2);

             TableCell msgCell = new TableCell();
             msgCell.CssClass = this._EmptyDataCellCssClass;

            if (this.EmptyDataTemplate != null) //the second row, use the template
             {
                this.EmptyDataTemplate.InstantiateIn(msgCell);
             }
            else //the second row, use the EmptyDataText
             {
                 msgCell.Text = this.EmptyDataText;
             }

             msgCell.HorizontalAlign = HorizontalAlign.Center;
             msgCell.ColumnSpan = this.Columns.Count;

             row2.Cells.Add(msgCell);

             t.RenderControl(writer);
        }

         protected override void   Render(HtmlTextWriter writer)
         {
            if ( _enableEmptyContentRender && ( this.Rows.Count == 0 || this.Rows[0].RowType == DataControlRowType.EmptyDataRow) )
             {
                 RenderEmptyContent(writer);
             }
            else
             {
                 base.Render(writer);
             }
         }

     }
}