I've run into an issue where a third-party component appears to be interfering with Response.Write and causing any content within Response.Write("") to render before any of the other html. For example:
<html><head><title><% Response.Write("HELLO WORLD") %>
will render as
HELLO WORLD<html><head>...
However, any content rendered using <%= %> blocks will work correctly. The below code will work perfectly:
<html><head><title><%="HELLO WORLD"%>
I always assumed that <%= was simply shorthand for Response.Write. From what I've been able to find on MSDN I now understand that it <%= is eventually converted to Response.Write, but apparently there are a few steps inbetween.
Does anyone have a guess as to why the two would render differently or point me to some documentation/info that explains how <%= %> blocks are handled?
Update: The control that was causing the issue was the Telerik AjaxManager control from the 2009 Q1 release. Upgrading to the Q2 control resolved the problem.
Unfortunately I don't have access to the source so I haven't been able to figure out why the control was causing this behavior. The issue has been resolved but I am still very curious as to why it existed in the first place.
<%= "foo" %> is turned into Response.Write("foo"); once it is compiled. You can verify this by digging through the ASP.NET Temporary Files folder and using Reflector to decompile the dll's you find.
Related
Is it possible to do something like this inline in an ASPX page?
<%= Me.SomeExtensionMethod() %>
I can't seem to figure out how to get this to work properly. I'm receiving an error saying that "SomeExtensionMethod" is not a member of the current Page object. I've added the necessary <%# Import Namespace="..." %> directive at the top of my page. This Does work in code-behind.
This isn't vitally important, but it would be good to know how to do in the future.
Thanks!
Adding imports in the namespace works for me!
<%# Import Namespace="Foo.FooFoo" %>
Try closing the .aspx page and opening it up again as per this answer. If that improves things at all (e.g. enable intellisense) but doesn't solve it, please post any new errors you get.
You could also add the Public modifier to your Module or class definition. If you're using Modules, it really doesn't make sense to me that it would be required, but some discussion on this forum indicates that it might help.
If it's working in the codebehind, add the namespace to the function call:
<%=MyNamespace.ExtensionFcn("hello, world") %>
I'd do this before I'd modify the web.config.
I am working on an old Web Forms application with a lot of <%= %> bee sting code nuggets. I would like ReSharper to flag these and suggest replacement with the encoded version <%: %> (see here).
I have tried to create a custom pattern via this article, however I am not sure what to use as the placeholder between the opening and closing tags. The only placeholder types that seem available for ASPX pages are tag name, attribute, attribute value, and content placeholder. None of these seem to select (find) the value in the bee sting code nugget.
Since I only really need to find/replace the opening tag, I tried just using <%= as the pattern (eliminating the need for a placeholder), however ReSharper does not let me save it. It requires the closing tag to be in the pattern to save.
How can I configure ReSharper to suggest replacing <%= %> with <%: %>?
In ASP.NET, what functions are allowed inside the <%# %> tags? I frequently use Databinder.Eval(), and I know some basic things like CStr(), but where can I find a complete list with documentation? I would look myself, but honestly I don't even know what the name of the <%# %> tags are.
It's funny that nobody really knows what these are called - I think in the ASP.NET MVC team they call them Code Nuggets. Others call them Code Rendering Blocks.
Anyway, this is essential reading: http://quickstarts.asp.net/QuickstartV20/aspnet/doc/pages/syntax.aspx
Here is some specific info on the <%# Data Binding Syntax: http://msdn.microsoft.com/en-us/library/bda9bbfx%28v=VS.100%29.aspx
And this helped me understand the Eval voodoo: http://weblogs.asp.net/rajbk/archive/2004/07/20/what-s-the-deal-with-databinder-eval-and-container-dataitem.aspx
Anything that is in scope. E.g. public/protected methods on your page, public methods in some referenced namespace/class, etc. In addition to things that are related to the current NamingContainer you're within.
A simple question, I think:
I want to put a tag into an ASP.NET app I've been asked to maintain, so I'm coming at this from a newbie point of view just tinkering around the edges without knowing a lot.
I wrote an old ASP application back in 1998, so I am just running on memory...
How do I write some output to the webpage?
I know I can use an
<asp:label id="blah">
but then I need to define a Label blah; in my code behind and then assign it.
I believe that I can put in-place:
<% Response.Write("sometext"); %>
and that will write sometext in the location within the page. (Am I correct?)
Lastly, I remember there was a syntax to the effect of
<%= "some string" %>
but I can't find the documentation on it, to say either it is deprecated, unadvised, or the rationale for such a decision.
I have tried googling for "ASP.NET grammar" but I can't even find a good description that "<%=" even exists, though it is mentioned in a few blogs.
For something simple, like inject the global version number, or the current date, then I can't see anything particularly wrong with in-place composition - it would save me defining 15 labels and having to initialise them all - though perhaps the asp:label approach could reference one global instance of a label?
Just asking for opinions on good practices :)
<%= string %> is perfectly valid ASP.NET syntax. The reason you will often find references to problems with using that is people use <%= (equivalent to Response.Write) when they should use <%# (for databinding) or vice-versa.
For example, we use it very extensively in our content managed site, where we pull in values from a global settings repository:
<%= SiteContext.Current.GetSetting("SiteTitle") %>
MSDN:
MSDN entry on <%= (this is under the JScript.NET section but still applies)
MSDN entry on <%#
Some others suggest <%= is not a "best practice" or a very good approach, but I strongly disagree with that sentiment. For an MVC-ish type site (especially a site that is template- or view-driven in some way), the most direct approach is frequently more effective than using server controls.
Just be mindful that when you use an <asp:Label /> it renders the .Text inside the <span> tag whereas an <asp:Literal /> adds no extraneous HTML to the string passed to it.
For example, if you were building a content management system and wanted to display user-driven HTML, a Label control would not correctly display the output from a WYSIWYG type rich textbox whereas a Literal control is the appropriate choice.
The <%= %> is the late-bound equivalent of the Literal's .Text property. The only difference here is when the value is placed in the page (aside from obvious syntax and separation of concerns paradigm) during the course of the page lifecycle.
Since the .Text property is on a control inherited from WebControl, it can be set/read/manipulated during any of the events following the control's Load event (wherever/whenever you load the control inside the page), but the <%= %> text cannot be directly read/used/manipulated by the code-behind without referencing some other control to get to it (like a containing div's InnerHtml property).
There are lots of options. You could use a single label, and string concatenate all the data you want displayed in that location.
You could create a user control with the layout you want and assign values that way.
You could inject it directly with response.write or the <%= %> syntax
You could create an HtmlGenericControl in your code behind (it's a div), add some text to it, and inject it into the pages controls collection.
Whatever you pick, try and go with the existing style of the coded page.
Look up the term "render blocks" for the <% %> syntax.
How about using
<asp:Literal id="z" text="goofy" runat="server" />?
Labels are usually used with forms.
You can also take full control of the rendering of your pages and controls and compose whatever you need to. You control the HTML, the order of rendering your controls, etc...
Go with the <asp:label /> (or a literal control if you want to customize some html in the content). Seriously. I'ts not that hard: when you put label in your markup visual studio will create it in the code-behind for you, so there's no extra work involved.
You could use the <%= "some string" %> syntax in web forms, but there can be issues when mixing that with the asp controls and there's a good reason new frameworks moved away from mixing logic like that in with your markup.
I have some code in my master page that sets up a a hyperlink with some context sensitive information
<%If Not IsNothing(Profile.ClientID) Then%>
<span class="menu-nav">
<a target="_blank"
href=
"http://b/x.aspx?ClientID=<%=Profile.ClientID.ToString()%>&Initials=<%=Session("Initials")%>"
>
Send
<br />
SMS
<br />
</a>
</span>
<%End If %>
<span class="menu-nav"> <!-- Name __o is not declared Error is flagged here-->
Now the issue seems to be in the href part. If I remove the dynamic code the error disappears. Can anyone tell me how to resolve this issue?
I've found the answer on the .net forums. It contains a good explanation of why ASP.Net is acting the way it is:
We have finally obtained reliable repro and identified the underlying issue. A trivial repro looks like this:
<% if (true) { %>
<%=1%>
<% } %>
<%=2%>
In order to provide intellisense in <%= %> blocks at design time, ASP.NET generates assignment to a temporary __o variable and language (VB or C#) then provide the intellisense for the variable. That is done when page compiler sees the first <%= ... %> block. But here, the block is inside the if, so after the if closes, the variable goes out of scope. We end up generating something like this:
if (true) {
object #__o;
#__o = 1;
}
#__o = 2;
The workaround is to add a dummy expression early in the page. E.g. <%="" %>. This will not render anything, and it will make sure that __o is declared top level in the Render method, before any potential ‘if’ (or other scoping) statement.
An alternative solution is to simply use
<% response.write(var) %>
instead of
<%= var %>
Yes, I have experienced the same bug occasionally in pages that use server side constructs on ASPX pages.
Overtime, I found a fix for it (I'm sorry, I just haven't been able to find out where I found this bit of info again.) and that fix is to put the following code above the errant <%...%> block:
<%-- For other devs: Do not remove below line. --%>
<%="" %>
<%-- For other devs: Do not remove above line. --%>
Apparently, where you put the above code makes all the difference to VS.NET, so it may take a few tries to get it right.
This is an odd solution, but for me I managed to fix this problem by simply closing the offending open files in Visual Studio.
With them open, i was erratically getting the __o problem.
As soon as I closed them, the __o problem disappeared.
After some hours of googling and analyzing bunch of aspx'ses in my current project seems I've found the solution, that is working for me. Would to advise strongly avoid html-style comments:
<!-- ... -->
inside aspx page. Instead of it use aspx-style comments
<%-- ... --%>
Additionally it helped me obtain that vs intellisense and code highlighting became working again and the mainly thing - this case had begun from it - vs can now hit the breakpoints inside embedded pieces of vb/cs code! And no any damn "This is not a valid location for a breakpoint" message.
When I've cleaned the solution, restarted IIS and it is still mysteriously playing up, I find this can sometimes be caused by pasting an ASPX source file's contents from another system into Visual Studio which "helpfully" updates the code, possibly changing some IDs and breaking the page.
Pasting it into another editor (Notepad++?) then saving it stops Visual Studio from "being helpful" and the page works again.