I am building a set of asp.net server controls and in one of them, essentially a container control, I want to add a form control, a script manager and an update panel. Is this possible or will I have to create these in a Page base class that I have for the web project for page/control life cycle reasons?
I am not using master pages.
Regards,
Andrew
ASP.NET allows only one form on the page. When you create controls, they are used on a page. You need a Page object to add controls to. This is why controls like the form and ScriptManager (who can only have one instance on a page) are put on the Page itself, or on the masterpage (if you have one). Putting them in a control would provide the opportunity to have two instances on the page, which would not work.
Related
I'm working on a .NET WebForm app which has a master page. The .NET can not recognize many elements in the aspx file. For example it say Label is not a valid asp element and then says most likely reason is a malformed web.config file.
I double check my web.config and all looks good. The other webpages do not have same issue. The interesting thing is I do not have this issue inside the MasterPage.
I also tried recreate the page from scratch but still having same issue.
I'm using VS2019. Framework 4.6
You have to provide some sample code and markup. Also, if you have a master page, then that is a huge deal also. As a general rule, asp.net controls you drop on the page are able to be used from code behind. However, the code for the standard page(s) that we use as a "child" of a master pages means that code behind for the master page can easy use controls in master page. And code behind for the page being displayed in that master page ALSO can freely use its own controls. But controls between the master page and the working child page is VERY different matter.
And of course controls dropped into a repeater, or say listview (or even gridview) means that the one label or text box control is automatic repeated over and over. As such, you have to pull/get/use the one row out of that data bound repeating control, and then from that one repeating row grab the control in question.
So, saying I can't start my car, or I can't use or get a control?
We need more information as to the context of what control, where it is (in the master or child), and is the control perhaps nested inside of a data bound repeater, listview, gridview etc.
so, edit your question - add some details as to the markup, where it is (master or the child page), and we can help.
So, as a general rule, code behind in master page is free to use controls in the master page.
And in the web page you created, once again code behind is free to use controls in that page.
It can be more difficult to say have code in master page, and have it reference controls in the child page that is being displayed. But, then again, it is VERY rare that code in master page would need to reference or play with controls in the child page, since a master page will (usually) just be your main navigation bar - and it will be the same for many if not all pages you display - hence you master page really can't know what controls will exist in the current child page being displayed.
I am trying to use existing functionality which is embedded in a asp.net aspx page. So I have controls on this page and code behind for it. What is the best way to reuse this functionality in a new ascx control? Or do I just have to copy everyting into the control?
Can you not just take the controls you want to use from the aspx page and turn those into a control? Then you can use that control wherever you like.
To access the page parent just written this.Page in your control. But for access to these methods, you must apply an interface to the aspx page.
I am studying ASP.net webforms and i am confused where to placed Datagridview and other Controls
from webpage.aspx or in a Control.ascx .
//Which Validation and CRUD operations was performed
Which is the Best Practice.
Thanks in Regards
ascx
- fragment
- re-usable you can place it anytime in your webpages(aspx)
- Need to attached to aspx to make it works
aspx - the actual page it self which you call on your browser which your ascx are placed
have a look at this same post:
Post 1
post 2
Building User Controls
Regards
You can put the thing in both but its depends on your requirement
aspx - is asp.net page so when you put control on it , it get utilize with in that page only i.e not resuable.
ascx - is user control , i.e usable control with in your application . once you design it you can use it in any page of by registering it on page.
so go for ascx when its resuable and going to use in no pages. go for aspx when its page specific.
If you want your DataGridView (maybe including some search form, button) appear on every page. Then use ascx. Else aspx. Ascx is a page fragment, not page!
I have a certain page and depending on an administrator role a lot of extra validation controls have to be inserted. However I don't want to take the risk that a validator gets turned on for other users.
What I was thinking is to use some form of "Visual inheritance" but I don't know which path to choose. Perhaps have separate .aspx pages which inherit from the same class (which inherits from Page)?
Side note: this has to be done in webforms, not mvc.
Extra information: The problem I'm trying to solve is the separation of roles and the impact on the page without having to duplicate the page and having to maintain any changes in both. There are clients who get to see the vanilla page and admins can see the same information but with added validation controls. However these validation controls should not be seen by the clients. Also some more information can be seen but that could be handled by using rolebased viewing of certain user control.
Anyone has an idea about this?
Why don't you want to use master pages? Master pages do exactly what you want to do - they can even "inherit" from each other (in a manner of speaking).
I would suggest that you use master pages to do what you want.
ASP.NET master pages allow you to
create a consistent layout for the
pages in your application. A single
master page defines the look and feel
and standard behavior that you want
for all of the pages (or a group of
pages) in your application. You can
then create individual content pages
that contain the content you want to
display. When users request the
content pages, they merge with the
master page to produce output that
combines the layout of the master page
with the content from the content
page.
If the problem you are trying to solve is role based viewing of controls and you are using the builtin asp.net membership/roles providers, you could use the LoginView control to manage the visibilty of the admin stuff:
<asp:LoginView runat="server" ID="LoginView">
<RoleGroups>
<asp:RoleGroup Roles="Admin">
<ContentTemplate>
Special Admin content
<asp:RequiredFieldValidator></asp:RequiredFieldValidator>
</ContentTemplate>
</asp:RoleGroup>
</RoleGroups>
</asp:LoginView>
Often such problems can be solved by splitting the page into user controls (.ascx). It can become a bit messy, but gets the job done.
Inheritance of pages is difficult, although possible. What you must realize, is that one .aspx page cannot inherit from another .aspx page. This is because of how the ASP.NET compiler works: your .aspx XML markup is compiled into a class that derives from your code-behind class. Since this only happens at runtime, you cannot have another .aspx page inherit from it, because the class is simply not there when the code-behind is being compiled.
What you can do is to create another class that inherits from Page and make your .aspx code-behind classes inherit from that. That is possible, but note that this class will not have an .aspx XML part - you will have to instantiate all the controls yourself, as well as assign their properties. In most cases this will be quite messy.
If they are different, under what circumstances should we decide to use either approach?
Also, what is the advantage of ascx over aspx?
user controls are a form of custom control, that gives you a visual designer. They are ideal for use when you want a reusable control within the same web site. (It is possible to create and package user controls as seperate assemblies but that is beyond the scope of this question and I know has been asked on SO).
A custom control is typically used to refer to a Web Control, or a Composite Control which is specialized form of a web control. These controls have no designer and are usually implemented in seperate projects from your web allowing them to be reused accross many sites.
Now your second question, ASCX and ASPX are two different things. ASCX is the extension for a User Control, where as ASPX is an ASP.Net Page. You cannot use an ASCX by itself it must be placed onto an ASPX or Master page.
One way I like to use user controls is I have for example a very complex page which have 7 tabs, 5 of those have grids, of those grids three of them are identicle. Well what I can do is create a seperate user control for the content of the tabs, this now reduces the code I need down significantly (Since three grids are identicle except for the data).
Further more it allows multiple to work on various parts of the page, and it helps me keep everything straight since I am reducing the complexity of the page. You do not use User Controls instead of Pages, you use them in conjuction with a page.
Edit
You do not use ascx over aspx. You use ascx to complement. For example on my site every page has the same footer, but I don't want every page to derive from a single master page. I can create my footer as an acsx control and put it in each of my master pages.
Another example, I have a form that lets a user enter three different date ranges. (And we have other forms). So I put the logic to enable a calender button, and a text box that when clicked on opens up the calender, in a user control. I can then reuse that user control in all my aspx pages.
Custom controls are control build entirely in code. The pro is that you can put them in libreries, add an icon to the toolbox and other fine control.
User controls are more easy to do, and in general is a way to encapsulate things to simplify other pages or when you need to use the same markup in several pages.
The advantage of controls over regular aspx pages is that you only need to do some part of the markup (not the whole page)
User Controls/Composite controls
User controls that are made up of other ASP.Net or custom controls. They are usually quite straight forward and can be created quite quickly. They Are generally not shared across projects however there are some tricks that can allow you to do this.
Custom controls
Custom controls are controls that you implement the UI by creating everything from the HTML output to design time support. Custom controls take much longer to make. You must use either Web.UI.Control or inherit from a sub control (Textbox for example). Custom controls are compiled to binary format to allow them to be distributed more easily. Since they are compiled they can be referenced from the toolbox in visual studio.
There are 2 main advantages to using a control in an aspx page. Encapsulation of logic and reuseability.