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SharpDevelop - Broken link between .aspx and .aspx.cs files

I have just started using SharpDevelop and I am trying to convert a Visual Studio Express website project into a SharpDevelop one. I managed to create the solution fine and the project within it. This is a C# ASP.NET webforms project by the way. Just simple aspx pages with C# codebehinds and an .asmx webservice in there. Nothing special and in fact quite old fashioned stuff, which worked fine in Visual Studio.
I am liking the SharpDevelop environment so please don't answer with "why not use Visual Studio instead" (I have reasons). But here is my problem:
SharpDevelop is not linking the .aspx files with their .aspx.cs counterparts. So instead of the solution explorer showing MyPage.aspx which you then expand to see MyPage.aspx.cs under it, you see them as two distinct separate files next to each other and unrelated.
And when I compile the solution I get an error because the codebehind can't tie itself to the aspx page and doesn't recognise the control names. (Example below is from my Contact.aspx page but it happens on every page where I have any server-side asp.net control).
The name 'EmailAddress' does not exist in the current context (CS0103) - Contact.aspx.cs:52,100
Now keep in mind this never used to happen in Visual Studio, so something has gone wrong in my SharpDevelop solution. The error occurs anywhere in the codebehind (.aspx.cs file) which refers to:
EmailComments.Text
Things I have already checked:
1) The #Page directive is correct and the Inherits name matches the class name.
2) The .cs and .aspx filenames and class names all match.
3) The .net framework version is 4.5 (does this make a difference?)
4) I have tried explicity declaring the asp.net controls in the codebehind and yes this prevents the error however the link between files remains broken and why should I have to declare the control in the codebehind anyway? Never used to in Visual Studio and it worked fine there.
Wierdly there is one file in my entire solution which does not have this problem (the aspx and aspx.cs files are linked fine) and this is the default.aspx page. There is nothing different about it. The only thing I can see is that it's a lowercase filename whereas the others are mixed case. (Surely that's not relevant?)
I would really appreciate help from anyone familiar with SharpDevelop or if it's a more general .net issue then please tell me. I feel as if there is some basic thing I am forgetting that will make this work.
Thank you very much for any help.
UPDATE: I have managed to link the .aspx and .aspx.cs files by doing the following: Drag and drop the .aspx.cs file on to the .aspx file in the solution explorer. Do this for every pair of files. Then save and close the solution and re-open and they remain linked. BUT, the error remains as per above because the codebehind does not recognise the controls referred to in it.

You may have a website or a "web application" project. There are differences in how code-behind is wired up between the two. Most importantly you may need CodeBehind instead of CodeFile attribute in your page directive. See http://msdn.microsoft.com/en-us/library/vstudio/dd547590(v=vs.100).aspx#summary_of_differences
Hope this helps.

Designer.cs gets corrupt after making changes to the webpage in Visual Studio 2010

Visual Studio isn't behaving normally when I make a change in an aspx file. It makes changes to the designer.cs file. These changes mean that I cannot access any of my controls by their ID in my code behind file.
When I revert the changes (using SVN), that have been made behind my back, in the designer.cs file, my build succeeds again and everything works fine.
I see that Visual Studio deletes a lot of lines in the designer file.
I've read some similar issues on the web but I can't find a good solution for this.
Has anyone of you experienced the same problems with Visual Studio and can help me solving this?
Update: I found that Visual Studio adds this line to the designer.cs:
protected global::System.Web.UI.WebControls.UpdatePanel UpdatePanel1;
But this should be:
protected global::System.Web.UI.UpdatePanel UpdatePanel1;
When I make this change manually in the designer.cs file, it works. But every time I make a change to the aspx file, Visual Studio creates again the wrong reference.

im having the same issue. my workaround is moving the definition from the designer file to the code behind file and defining it properly as:
Protected WithEvents UpdatePanel1 As Global.System.Web.UI.UpdatePanel
instead of letting designer keep overwriting it improperly as
Protected WithEvents UpdatePanel1 As Global.System.Web.UI.WebControls.UpdatePanel
im using vs2013 vb.net asp web forms application.
i've also seen suggestions to change the target framework in the web.config file to 4.0 (did not work for me, im targeting 4.5, was getting the problem with both targets)
and i also saw a suggestion to use the Register tag like:
<%# Register TagPrefix="asp" Namespace="System.Web.UI" Assembly="System.Web"%>
at the top of the page. this did resolve the 'error' that was being thrown when i tested it, however it caused numerous 'warnings' to appear for all of my asp tags.

My office is plagued by this issue in Visual Studio 2013. We were using the following workaround:
Right-click on the project and select Properties.
On the Application tab, change the Target framework version and save the project.
Repeat steps 1 and 2 to set the target framework back to the one you want.
Save the .aspx file again.
This would work 100% of the time, but we discovered that it messed up some of our web.config settings.
We are now using the following workaround, which also seems to work and does not make any breaking changes to the project config files:
Right-click on the project and select Unload Project.
Right-click on the project and select Reload Project.
Save the .aspx file again.

Make sure that the class name of the cs file is the same as the designer.cs and check the Inherits attribute of the page in the aspx file is the same. Also check if there is any class in your project with the same name as your page class name, also i would like to know the error that appear when you make any updates in the aspx page.

Designer.cs not updating when new controls added to .aspx

I've added a new control to my aspx files and noticed that not only was the new control not added to the designer file but that it was also missing quite a few other controls that were added by other members of the team. I've tried deleting the designer.cs file and using "Convert to Web Application" with no success. Some other things i've tried have been excluding the aspx from the project, building, and then re-including with no success. I've also manually entered in a control that was missing in the designer into the designer. When I run after do so an error appears saying the control isn't defined, even though it actually is, and that I should check if I'm missing a directive.
The first control I added was copy and paste from a similar control and made necessary changes. But, i've also tried manually creating the control with the same results.
Any ideas?

Try this
1.- Change CodeBehind="Name.aspx.cs" to CodeFile ="Name.aspx.cs"
2.- Build
3.- Change CodeFile ="Name.aspx.cs" to CodeBehind ="Name.aspx.cs"

I've been suffered this problem in my work.
The surest thing is you regenerate your .designer.cs file, and here is the solution:
Locate the corrupted aspx.designer.cs file through the Solution Explorer
Delete only the designer.cs file from your project
Rightclick your main aspx file and select “Convert to Web Application“.

For me the solution was to:
Put your page in design view and right click / refresh. It will sync
the controls with the designer.cs. Make sure designer.cs is close
before doing this.
Source

Close Visual Studio, then delete Temporary ASP.NET Files from C:\Windows\Microsoft.Net\Framework\Your_.Net_Version\ProjectName Delete the folder ProjectName and re-start Visual Studio. I had a similar issue some time ago and it was solved by these actions.
If you use IIS, you may need to stop the server/site to be able to delete the temp files.

To replace the designer file in VS 2013:
Delete the old *.designer.cs file
select the *.aspx file
Select “Convert to Web Application“ from the Project top drop-down bar

I did this in VS2012:
Open the page.aspx.designer.cs Find a control declaration of the
same type of control (ie LinkButton)
Copy it to the end of the file (before the end of class curly bracket)
Rename the control variable to match the name of your control.
That's it.

In my case, I had to add the runat="server" attribute then to rebuild the solution. The missing elements were automatically added to the generated aspx.designer.cs and become available for use in code
<button runat="server" id="Button01" type="button" class="Button" onclick="location.href='http://http://www.example.com/';">
<asp:Label runat="server" Text='<%# GetText("Button01")%>'></asp:Label>
</button>

One simple/stupid mistake that also results in similar symptoms is if you copy aspx and aspx.cs files and rename them, but neglect to update the references inside the file.
I came across this question trying to find the temp asp.net directory, but clearing that didn't help. I then realized that I did not update CodeFile="Page.ascx.cs" after I had copied the files to create a new modified version of the page. Then i was trying to add a control and reference it in PageModified.ascx.cs but kept saying it didn't exist.

This also seems to happen when you have a usercontrol that references another usercontrol in the same namespace.
if you move the referenced user control to a different namespace the problem goes away

Sometimes there might be errors in html like two controls having the same Id. Also be careful with div and span tags. These stops the designer from getting updated. For all of these, check the warnings in Error List and fix them. You are ready to go. This solved my issue.

I was able to solve the problem only manually adding the control declaration inside the code behind file. Every time I tried to regenerate the design.cs file, VS 2013 would write the same lines without the missing control.
The declaration needs to be added in the code behind, NOT in the design.cs, because it would be deleted each time the .aspx is changed.
Just add the declaration like you would do for any other variable, something like this:
protected MyNameSpace.MyControl ControlName;

Just to add to the list of possible solutions: These lines in my markup file, although seemingly valid, were apparently causing a disconnect with the designer file:
<%: Styles.Render("/my-file.css") %>
<%: Scripts.Render("/my-file.js") %>
I simply commented them out, saved, and the designed file began working correctly. I then uncommented both lines, saved, and was able to add new controls to the page without issue. I found this strange, and it's still unclear to me what the initial cause of the problem was. I can only speculate that it's a Visual Studio bug.
Point being, there may be perfectly valid code that's causing an issue, in which case, a possible solution would be to go through commenting HTML sections out in your markup file until the designer file resolves itself, and then you can undo all your commenting and resume working as normal.

I tried all of the above in VS2019.
I deleted the designer file, clicked on the Project Menu / Convert to Web Application which rebuilt the designer file, however, it still wouldn't auto regenerate.
What worked - excluded the file from the project, then reincluded it.
The file now keeps auto regenerating.

For creating a code-behind C# file with Visual Studio 2019 from inline ASPX code, I had success with the following procedure:
Create CS file with the same base name and '.cs' extension, using Project/AddClass from the main menu.
Move all C# code from the ASPX file into this new file. Add the following code to this new class:
namespace <<your_namespace>> {
public partial class <<your_class_name>> : System.Web.UI.Page {
Add / modify the 1st line of the ASPX file:
<%# Page Language="C#" AutoEventWireup="true" CodeBehind="<<your_class_name>>.aspx.cs" Inherits="EVV.pages_sqlserver.<<your_class_name>>" %>
Create CS file with the same base name and '.designer.cs' extension, using Project/AddClass from the main menu.
Copy the contents of any other .designer file. Remove the complete contents of the class, only curly brackets remain.
Open the form designer for the basic ASPX file. Right-keep any empty area and select Refresh. Sometimes, this is sufficient. If not:
In Solution Explorer right-click the same ASPX file and select Publish.
Sometimes it only worked after closing Visual Studio, deleting all temporary files and reopening the solution.
** Update: in Visual Studio: 16.6.3 this seems to be broken: it sometimes works, sometimes not. Even for completely new WebForms, there is no update on the Designer file. **
** Update 2: This does not work reliably. I switched to Redesigner (https://github.com/seanofw/Redesigner/tree/branches/net40) which is working like a charm.

My designer.vb code file was not updating because of an error in Telerik web controls - I had an incorrect value in the DataKeyNames attribute of a MasterTableView. The aspx editor did not pick this up at design time as it's simply a string value, but it was causing the autogeneration of the designer.vb file to fail.

In my case it helps just to change "ID" attribute of control in ascx file to some other value first, and then back to desired. It leads to refreshing of ascx.designer.cs file. Simple trick in case C# code is not generated for your control yet for some reason...

For me the solution was:
I deleted the designer file.
Recycle bin and restore the same file.
In visual studio solution explorer, click on show hidden items from top and include the same file to the ascx file.
Right click on ascx page and click on view designer. (optional)
On the designer, right click and refresh and save. (optional)

As a solution right clicked on the aspx.cs page and selected move... into and choose the

Make sure your control is in the page's scope. In my case, it was in a Repeater template.

Parser Error on all new aspx pages in IIS7

I have a web site where any new aspx pages throws a "Parser Error". It has existing pages, and I can change the html or the c# code in it, and the change will appear in the web page in the browser.
The error page gives a message of "Could not load type classname". I've tried adding several different pages in Visual Studio, and copying the pages to IIS, so the syntax of the page should be fine.
I;ve also made sure that the "Inherits" attribute has the correct class and the class exists. I'm completely stuck.

Have a look at the Directive at the top of the page. Does it have a CodeBehind attibute? If so change it to CodeFile, and try the page in the browser again.
If that doesn't work, compare the top part of a non-working page and a working page. Would be a little easier if you could post the top parts of the page here.

One thing that popped to mind immediately is to make sure that the target version of the .NET Framework for your web site is the same as the one specified for the application pool in IIS in which the site is running.
Right-click on the web site in Visual Studio and check the "Target framework" setting. Make sure this matches the ".Net Framework version" setting in IIS.

Are you using any usercontrols? Is your project set up as a web Application project or website?
If you are developing a web application project and you copy a new file or add a page without using the add new by right clicking you may have some page files that lack their designer files.
If that is the case then I suggest right clicking any page missing the designer file and click "Convert To Application" Then rebuild your solution

The name 'controlname' does not exist in the current context

I have a web application that I'm working on (ASP.NET 2.0 with C#, using Visual Studio 2005). Everything was working fine, and all of a sudden I get the error:
Error 1 The name 'Label1' does not exist in the current context
and 43 others of the sort for each time that I used a control in my code behind page.
This is only happening for one page. And it's as if the code behind page isn't recognizing the controls. Another interesting thing is that the IntelliSense isn't picking up any of the controls either..
I have tried to clean the solution file, delete the obj file, exclude the files from the project then re-add them, close Visual Studio and restart it, and even restart my computer, but none of these have worked.

I know this is an old question, but I had a similar problem and wanted to post my solution in case it could benefit someone else. I encountered the problem while learning to use:
ASP.NET 3.5
C#
VS2008
I was trying to create an AJAX-enabled page (look into a tutorial about using the ScriptManager object if you aren't familiar with this). I tried to access the HTML elements in the page via the C# code, and I was getting an error stating the the identifier for the HTML ID value "does not exist in the current context."
To solve it, I had to do the following:
1. Run at server
To access the HTML element as a variable in the C# code, the following value must be placed in the HTML element tag in the aspx file:
runat="server"
Some objects in the Toolbox in the Visual Studio IDE do not automatically include this value when added to the page.
2. Regenerate the auto-generated C# file:
In the Solution Explorer, under the aspx file there should be two files: *.aspx.cs and *.aspx.designer.cs. The designer file is auto-generated.
Delete the existing *.aspx.designer.cs file. Make sure you only delete the designer file. Do not delete the other one, because it contains your C# code for the page.
Right-click on the parent aspx file or Project menu. In the pop-up menu, select Convert to Web Application.
Now the element should be accessible in the C# code file.

Check your code behind file name and Inherits property on the #Page directive, make sure they both match.

exclude any other pages that reference the same code-behind file, for example an older page that you copied and pasted.

I had the same problem. It turns out that I had both "MyPage.aspx" and "Copy of MyPage.aspx" in my project.

Also, make sure you have no files that accidentally try to inherit or define the same (partial) class as other files. Note that these files can seem unrelated to the files where the error actually appeared!

I ran into this same error, except it was a WPF error. I was rearranging projects and had a control defined in like this:
<local:CustomControl Name="Custom" />
In my code behind I tried using Custom.Blah, but I got the error:
The name 'Custom' does not exist in the current context
What did the trick for me was changing my control in Xaml to this:
<local:CustomControl x:Name="Custom" />
Hope this helps someone out there!

I get the same error after i made changes with my data context. But i encounter something i am unfamiliar with. I get used to publish my files manually. Normally when i do that there is no App_Code folder appears in publishing folder. Bu i started to use VS 12 publishing which directly publishes with your assistance to the web server. And then i get the error about being precompiled application. Then i delete app_code folder it worked. But then it gave me the Data Context error that you are getting. So i just deleted all the files and run the publish again with no file restrictions (every folder & file will be published) then it worked like a charm.

I had the same issue, my problem was not having space between two attributes"
AutoGenerateColumns="False"DataKeyNames="ProductID"
instead of
AutoGenerateColumns="False" DataKeyNames="ProductID"

I fixed this in my project by backing up the current files (so I still had my code), deleting the current aspx (and child pages), making a new one, and copying the contents of the backup files into the new files.

this error often occurs when you miss runat="server" .

I had the same issue since i was tring to re produce the aspx file from a visual studio 2010 project so the controls had clientidmode="Static" property. When this is removed it was resolved.

I had a similar problem when tweaking with a Repeater after converting it from a DataList.
Problem was that I accidentally united 2 attributes when deleting an unneeded one.
<asp:Repeater runat="server" ID="ClientsRP"DataSourceID="ClientsDS">
.
.
.
</asp:Repeater>
And this prevented the generation of the repeater in the design file.

I had the same error message. My code was error-free and working perfectly, then I decided to go back and rename one of my buttons and suddenly it's giving me a compile error accompanied by that blue squiggly underline saying that the control doesn't exist in current context...
Turns out Visual Studio was being dumb, as the problem was related to the backup files I had made of my aspx.cs class. I deleted those and the errors went away.

In my case, when I created the web form, it was named as WebForm1.aspx and respective names (WebForm1). Letter, I renamed that to something else. I renamed manually at almost all the places, but one place in designer file was still showing it as 'WebForm1'.
I changed that too and got rid of this error.

1) Check the CodeFile property in <%#Page CodeFile="filename.aspx.cs" %> in "filename.aspx" page , your Code behind file name and this Property name should be same.
2)you may miss runat="server" in code

In my case I had to hunt through the 417 "controlname not found" errors to find an actual error: I had replaced a DLL but not updated the version number in the web.config. Fixed that and built successfully, 3 minutes after that all the other errors had resolved themselves.

Solution option #2 offered above works for windows forms applications and not web aspx application. I got similar error in web application, I resolved this by deleting a file where I had a user control by the same name, this aspx file was actually a backup file and was not referenced anywhere in the process, but still it caused the error because the name of user control registered on the backup file was named exactly same on the aspx file which was referenced in process flow. So I deleted the backup file and built solution, build succeeded.

I ran into this same issue. Apparently, you shouldn't call a class in the DLL the same name as one of the .aspx/.aspx.cs files. I thought they would not be in the same scope, etc. but it messed with Visual Studio's internal workings too much. I'm a bit surprised there isn't something to keep you from doing this if it is going to produce that type of error. Anyway, just delete the .aspx/.aspx.cs files and rebuild your project. Then bring them back in under another name. You can copy/paste your code into another editor if you don't want to retype it all back in.