为什么绑定表达式不适用于 C# 表达式? [英] Why doesn't binding expression work with C# expressions?
问题描述
The following code compiles, but doesn't work. As far as I know data-binding expressions allow any valid C# code in them. So what am I doing wrong here?
<asp:Panel CssClass='<%# ("my-class") %>' runat="server" ID="myPannel">
Blah
</asp:Panel>
<% this.myPannel.DataBind(); %>
I am not getting any errors. It just doesn't render the class attribute whatsoever. I tried without the parenthesis with the same bad luck.
Please note, I need an expression to be evaluated in CssClass attribute and I am expecting the result of that expression to be assigned to the class attribute. This is why I emphasized this by enclosing the string into parenthesis.
Try this:
<html>
<head runat="server">
<title></title>
<script runat="server">
protected void
Page_Load(object sender, EventArgs e)
{
this.myPannel.DataBind();
}
</script>
</head>
<body>
<form id="form1" runat="server">
<asp:Panel CssClass='<%# ("my-class") %>'
runat="server"
ID="myPannel">
Blah
</asp:Panel>
</form>
</body>
</html>
Or just switch the order of your inline code snippets:
<body>
<% this.myPannel.DataBind(); %>
<form id="form1" runat="server">
<asp:Panel CssClass='<%# ("my-class") %>'
runat="server"
ID="myPannel">
Blah
</asp:Panel>
</form>
</body>
Or simply use:
<% this.myPannel.CssClass = "my-class";%>
<form id="form1" runat="server">
<asp:Panel
runat="server"
ID="myPannel">
Blah
</asp:Panel>
</form>
In all three cases, you have to make sure that the control property is updated before the actual inline code of the control is being processed in the page's life cycle.
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