ASP.NET在绑定时使用条件表达式

ASP.NET在绑定时使用条件表达式

     Asp.net2.0不支持在数据绑定时的条件表达式。Asp.net 4.0已经平滑地解决这个问题，不用修改代码。
下面让我们来看一个简单的ASP.NET数据绑定场景，有这么一个Repeater：

 1:  <asp:Repeater runat="server" ID="itemsList"> 

 2:  <HeaderTemplate> 

 3:  <table border="1" cellspacing="0" cellpadding="5"> 

 4:  </HeaderTemplate> 

 5:  <ItemTemplate> 

 6:  <tr> 

 7:  <td align="right"> 

 8:  <%# Container.ItemIndex + 1 %>. 

 9:  </td> 

 10:  <td> 

 11:  <%# eval_r("Title") %> 

 12:  </td> 

 13:  </tr> 

 14:  </ItemTemplate> 

 15:  <FooterTemplate> 

 16:  </table> 

 17:  </FooterTemplate> 

 18:  </asp:Repeater> 

然后后端的cs:

 1:  protected void Page_Load(object sender, EventArgs e) 

 2: { 

 3: var items = new[] {  

 4:  new { Id = 1, Title = "Headline 1" }, 

 5:  new { Id = 2, Title = "Headline 2" }, 

 6:  new { Id = 2, Title = "Headline 3" }, 

 7:  new { Id = 2, Title = "Headline 4" }, 

 8:  new { Id = 2, Title = "Headline 5" } 

 9: }; 

 10: itemsList.DataSource = items; 

 11: itemsList.DataBind(); 

 12: } 

当我们需要判断绑定时数据行，我们需要Create这么一个类似的方法或函数：

 1:  /// <summary> 

 2:  /// Iifs the specified condition. 

 3:  /// </summary> 

 4:  /// <param name="condition">if set to <c>true</c> [condition].</param> 

 5:  /// <param name="trueResult">The true result.</param> 

 6:  /// <param name="falseResult">The false result.</param> 

 7:  /// <returns></returns> 

 8:  protected object Iif(bool condition, object trueResult, object falseResult) 

 9: { 

 10:  return condition ? trueResult : falseResult; 

 11: }  

然后在ASPX中使用它：

 1: <asp:Repeater runat="server" ID="Repeater1"> 

 2:  <HeaderTemplate> 

 3:  <table border="1" cellspacing="0" cellpadding="5"> 

 4:  </HeaderTemplate> 

 5:  <ItemTemplate> 

 6:  <tr style='background-color: <%# Iif(Container.ItemIndex % 2==0, "white", "whitesmoke") %>'> 

 7:  <td align="right"> 

 8:  <%# Container.ItemIndex + 1 %>.</td> 

 9:  <td> 

 10:  <%# eval_r("Title") %></td> 

 11:  </tr> 

 12:  </ItemTemplate> 

 13:  <FooterTemplate> 

 14:  </table> 

 15:  </FooterTemplate> 

 16: </asp:Repeater> 

这是在模仿VB中的IIF函数。到了ASP.NET 4.0中，我们可以直接这么写了：

 1: <asp:Repeater runat="server" ID="Repeater2"> 

 2:  <HeaderTemplate> 

 3:  <table border="1" cellspacing="0" cellpadding="5"> 

 4:  </HeaderTemplate> 

 5:  <ItemTemplate> 

 6:  <tr style='background-color:<%# Container.ItemIndex % 2==0 ? "white" : "whitesmoke" %>'> 

 7:  <td align="right"> 

 8:  <%# Container.ItemIndex + 1 %>.</td> 

 9:  <td> 

 10:  <%# eval_r("Title") %></td> 

 11:  </tr> 

 12:  </ItemTemplate> 

 13:  <FooterTemplate> 

 14:  </table> 

 15:  </FooterTemplate> 

 16: </asp:Repeater> 

http://blog.sina.com.cn/s/blog_3e29b20b0100il16.html