Use Code server-side scripting delimiters / ASP.NET inline expressions in none-ASP elements

Question

I get this error message:

Cannot create an object of type 'System.Boolean' from its string representation <%: false %> for the 'Visible' property.

When I try to run this code within my ASP.net website:

<a runat="server" visible='<%: false %>' href="~/" >Home</a>

Is there a syntax error? false should be replaceable by any method result same with:

<asp:Panel runat="server" Visible='<%: GetTrueOrFalse() %>'>Home</a>

Answer 1

Suppose you have a method that returns bool value like this:

public bool IsVisible()
{
    if (some_condition) // example condition test
    {
        return true;
    }
    else
    {
        return false;
    }
}

You need to use binding like this:

ASPX

<a runat="server" visible='<%# IsVisible() %>' href="~/" >Home</a>

ASPX.CS (Code-behind)

protected void Page_Load(object sender, EventArgs e)
{
    // do something

    Page.DataBind();
}

NB: This trick apply for either methods or properties which returns bool.

Update 1:

Since a tag doesn't set any id attribute, you can remove runat="server":

<a visible='<%# IsVisible() %>' href="~/" >Home</a>

Or use CSS with display: none or visibility: hidden:

<a visible='<%# IsVisible() %>' href="~/" style="visibility:hidden; display:none;">Home</a>

Reference:

Is code rendering block <%=%> useful for boolean type?