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Telerik mvc combobox: Prevent write value different from the list

I have a telerik combobox in mvc3 application and I want to prevent the user writing a value different from the list being loaded from the controller.
A thing that partial helped is to set the textbox input to be readonly but then:
1. The user can filter the list by the textbox.
2. The user can erase his selection.
Another thing that I thought about is: What the user types in the select is the value not the description, so I need it to prevent writing text different from the description while the value remains encapsulated.

Are you still looking to have the user be able to input custom text? If not you can use the DropDownList functionality as seen on this demo page.
If you still want the user to be able to type into the component but somehow have it aware of when they either misspell something, or type one character more than necessary, this can be extremely difficult. You would essentially have to have some clever JavaScript to be triggered with every key press and check the current value against a list. With users being pretty quick with typing, or their browsers being old, this can be very unreliable. Plus, a user can easily disable JavaScript at any time making this functionality obsolete.
I think your best options is to have it as is, where the user can type whatever they want. You can always have validation on the item they have typed and upon blur() or a POST (whatever fits your application) have a message appear to warn them of an invalid entry.

Detecting default button on a control

This seems very simple, but I can find nothing on a web concerning the behaviour I want to add to my custom control.
My custom control is a textBox with a list of choices. When the text entered by the user is not part of the list, a popup will appear with the list allowing the user to select a correct choice.
Sometimes, there may be a default button on the container in wich the custom control has been added. If so, when the enter key has been pressed, if the text is wrong, The popup must been displayed. If there is no default button, on enter, nothing must happen even if the text is wrong.
To be able to create this behaviour, I must be able to detect the presence of a defaultbutton in the container, and it must be done inside the c# code of the cutom control.
I hope the description is clear enough.
Thanks in advance

Have you thought about implementing an MVVM approach and the Command pattern? So long as your view model knows what the choices are, you can bind the default button to a command. So long as the commands CanExecute handler returns false, i.e., an appropriate choice has not been entered/selected, the button will be disabled and won't respond to the user pressing enter.

Since I was unable to know what other controls I had from the custom control I chose to go like this:
I made a recursive function to find the first parent using FrameworkElement.Parent
Having the parent, I could take a look at every controls it contains.
As soon as I saw a button, I had to verify if IsDefault.
For this one, I used the VisualTreeHelper GetChildrenCount(DependencyObject obj_Parent) and GetChild(DependencyObject obj_Parent, int childIndex). Recursivity once again...
It works very well even though it means more code to execute.

Is there a way to NOT load a specific control in ASP.NET/C#?

I've a container (RadDockZone - Telerik), and inside it, a textbox field with an "Asp:RequiredFieldValidator", which makes it mandatory. Every time that I work with AJAX operations, the entire container is "reloaded", including the RequiredFieldValidator. This makes the ValidationSummary show the same error message twice, until the page is completely reloaded (I'm using RadAjaxManager to solve the AJAX operations).
So, how can I "don't reload" a specific control (in this case, the RequiredFieldValidator) using C#?
Regards!

If you place the following in page load if(page.Isvalid) the required field validator will be fired once after submitting that form. The message will not be displayed twice.

If you do not include the textbox (or its wrapping containers) in the list of controls updated by the ajax manager, the textbox and the respective required validator should not be updated on ajax requests and the error message should not be visualized.

You should use validation groups. This lets you group all of your validation controls into a group. Then put this same validation group on your submit button and those validation controls will only validate when that particular button is clicked.
Property is assigned on the validation control and button using the ValidationGroup property.
Thomasvdb's suggestion of setting CausesValidation to false also might be a good way to do it.

Client side event handler on validation for asp.net validator controls

I have an asp.net form with bunch of sections that can be expanded/collapsed and are normally collapsed. Now, most controls on the form have RequiredFieldValidator or some other validators attached. If the user tries to submit the form with required fields not filled out, for m is not submitted but because most sections are normally collapsed, the user doesn't see the validator text (like exclamation mark on the right of a text box) prompting to fix the error.
What I want to do is for the controls that fail validation, to expand their parent containers so user could see those failed controls, but for that I need to hook up some client sode javascript that woudl execute when client side validation failed. I haven't foudn any way of doing it - validators naturally dont' expose those "validation events" to hookup to. Of course I can create my custom validators but that would mean rewriting (and duplicating functionality) completely all existing asp.net validators which sounds a big chunk of work.
Any ideas?
Thank you in advance!
Andrey

Here is how I solved a similar issue. For every validator that is added to the accordion, I store the validator id in an array, along with the accordion panel that it is contained in. I then pass this list to the client. I also hook into the OnSubmit event by calling Page.ClientScript.RegisterOnSubmitStatement. The javascript function that executes during the onSubmit first checks to see if the page is valid, if so then it just exits, if not then it loops through the list of validators looking for ones that are not valid, when it finds one, it expands the section associated with that validator.

Triggering multiple validation groups with a single button?

Let's say the page TestPage.aspx has two controls. The first control is an address control that has a validation group called "AddressGroup". This group contains several validation controls which are colated in the validation summary on that control. The second control is a credit card control and has a validation group called "CreditCardGroup". It also has several validators and a summary to display the results. To add to the problem, there are some random controls on the page that also have validators which are tied to a third ValidatorSummary control.
When the user presses the "Do it all" button, I would like the page to trigger all three validation groups. The button itself can be tied to a single group or an unlabeled group. It can not be tied to multiple groups as far as I can tell.
The solution is not to extract the validation from the controls as that would deminish the value of having them in seperate controls. Thanks for your thoughts.

Call the Validate method for each validation group individually inside the button's click handler:
bool isValidTest = false;
Validate("AddressGroup");
isValidTest = IsValid;
Validate("CreditCardGroup");
isValidTest &= IsValid;
// etc.
if (!isValidTest) return;
The next problem you may encounter is that the ValidationSummary control is linked to a single validation group. The only way that I've found to display all the error messages for multiple groups (without walking the control tree) is use multiple ValidationSummary controls.
With user controls, you may want to have its Validate method perform validation for all the controls it contains and display its own summary.
Edited to add: The isValidTest variable is not needed. According to the docs:
Note that when you call the Validate
method, the IsValid property reflects
the validity of all groups validated
so far.

Are you talking client side or server side validation? Jamie's answer is spot on for server side, but for client side validation you will probably need to write your own JS function that will trigger validation on all three groups in concert.

Call Page.Validate() on server side it will validate all the validators..