Question

I am trying to hide the button based on the user’s role using the following code:

 <asp:Button ID='btndisplayrole' Text='Admin Button' Visible='<%= WebApplication1.SiteHelper.IsUserInRole('Admin') %>' runat='server' OnClick='DisplayRoleClick' /> 

But when I run the above code I get the following error message:

Cannot create an object of type ‘System.Boolean’ from its string representation ‘<%= WebApplication1.SiteHelper.IsUserInRole(‘Admin’) %>’ for the ‘Visible’

Answer 1

Kind of an interesting issue.. But as the error message states, the string <%= WebApplication1.SiteHelper.IsUserInRole('Admin') %> cannot be converted to a boolean.

Unfortunately i cannot explain why the expression isn’t evaluated, but instead is treated like a string.

The reason why your <%# %> expression works as expected, is because it is treated much differently. When the Page is compiled into a class, then the compiler creates an event handler similar to this:

public void __DataBindingButton2(object sender, EventArgs e) {     Button button = (Button) sender;     Page bindingContainer = (Page) button.BindingContainer;     button.Visible = HttpContext.Current.User.IsInRole('admin'); } 

and hooks this method up to the Control.Databinding event on your control. As you can see, the <%# %> is this time properly treated as server code, and not just a random string.

So i guess the solution is either to use databinding, or go to the codebehind as AndreasKnudsen suggests.