Developing with XForms

Introduction

XForms contains logic to store and present forms and data posted from forms. Together with the forms editor in EPiServer CMS 5 Edit mode, it enables editors to create and modify forms and to view form data. The XForms architecture enables customization, allowing developers to adapt the XForms functionality. This technical notes describes how the technology is built up and answers common questions concerning EPiServer XForms.

Table of Contents

• Basic XForms Concepts
  » Folders for Forms
• XForms Forms Management Structure
• EPiServer.XForms Namespace 
  » XForm Class
  » XFormData Class
  » DataTypes Class
• EPiServer.XForms.WebControls Namespace
  » XFormControl Class
  » XForms Web Controls
• Sending Form Data
• FAQ

Basic XForms Concepts

Editors that create forms in Edit mode work with javascript to create an HTML version of the form. When saved, the content of the form is transformed using regular expressions and stored as a mix of XHTML and XForms markup.

When the form is presented, it is loaded as Web controls and rendered as HTML to the client, so there is no need to install any additional software to support XForms to the client.

Folders for Forms

Form folders make it possible to organize a group of forms in a folder structure, which can be useful if the site contains many forms. It is also possible to set a default folder for forms for either the entire Web site or parts of the Web site, making it easier for editors to manage forms. This is done by adding a dynamic property named "DefaultFormFolder" and then setting the property value to the folder of your choice for the part(s) of the Web site you want to affect.

When creating a new form page and selecting a form, the default folder will be the starting point for the form selection. When creating new forms, the default folder will be suggested. This property is supported, but is not included in the sample site and is, therefore, not included in the language files.

XForms Forms Management Structure

1. A form is created in the Form Editor in EPiServer CMS.
2. Through EPiServer.XForms, the form is converted to an XForm regular expressions. Steps 1 and 2 can be repeated until the form has the desired look and functionality.
3. Through EPiServer.XForms, the form is sent to the client as XHTML. It’s possible to alter the form before it is presented to the client by attaching to events.
4. Data is posted and validated. If the input does not pass validation, error messages will be sent to the client. (It's also possible to have additional validation on the client before sending the form to the server. This is done by setting the property EnableClientScript to true on the XFormControl web control.)
5. Through EPiServer.XForms, form data is passed into the EPiServer CMS data warehouse. It is also possible to send the posted data as an e-mail or to a custom URL.
6. If the data has been saved to the database, it is possible to load and show the posted data on the Web site.

EPiServer.XForms Namespace

XForm Class

This class is a representation of the content and structure of the form. The content of the form is saved as XML. The XML contains the instance node, which contains the data for the form such as field validation, default values for fields etc. It also stores information about the structure of the form. This is stored as XHTML with controls from the XForms namespace. This class is responsible for creating a default XFormData object from its instance node.

The following code shows an example of how an XForms form is stored.

XFormData Class

The XFormData class contains information on the content of a posted form. Normally a new XFormData class instance is created when a form is posted, but it is also possible to define an old post when loading a form to be able to re-edit data. This is also the class representing existing data when loading form data for a form.

DataTypes Class

The DataTypes class contains information on all the data types available for form fields. These are contained in a public property, Types, which is basically a hash table. The hash table simply contains keys and values, where keys are the unique key for the data type and the value is a regular expression.

When posting form data, all input will be validated against the regular expression for the data type of the input control. If no data type has been specified for the control, the data will be validated against the public string property “InvalidDefaultInputRegex”. The reason for having a default validation is to prevent malicious data being posted from a form.

EPiServer.XForms.WebControls Namespace

XFormControl Class

This is probably the most important class when working with XForms. XFormControl is a Web control that is used to display an XForms form and makes sure that the input is validated.

The class exposes a public method, SubmitForm, to be able to submit form data. The form itself does not trigger the actual posting. This is handled by any existing submit Web controls in the form, which is also why it is possible to have several buttons on the same form that may trigger different actions. It is, of course, also possible to call this method from the code.

What happens when the form is loaded?

1. The BeforeLoadingFormsEvent is triggered. It's possible to alter the xform definition here by changing the formDefinition property of the LoadFormEventArgs that are sent to the event handler. (For instance you could replace the table structure with a div structure by applying regular expressions to the form content).
2. The XML from the FormDefinition.Document property is parsed by Page.ParseControl. The parsed controls are added as child controls. Basically these would be Literal controls for the HTML and form Web controls derived from XFormControlBase.
3. For fields that have validation, validation control(s) will be added and connected to the corresponding Web control.
4. ControlsCreated  – public event is triggered. It’s possible to alter the appearence and funtion of the form at this time.
5. Rendering of the form takes place. All Xform controls are rendered as xhtml.

What happens when data is submitted?

1. The SubmitForm event for a submit control is triggered. If defined on the submit control, the submit will set values for e-mail and/or custom URL to the forms data property for the XFormControl that it is contained in. The SubmitForm method is called with the channel options set on the submit control. See Sending Form Data for more information on available channels.
2. Validation will take place to ensure that rules about anonymous users and several postings from the same user are followed. If there are validation errors against these rules StaticValidators will be added to the Page.Validators collection to ensure that validation errors will be thrown. A StaticValidator is a validator that will always give a validation error.
3. BeforeReadingPostedData – public event is triggered. If the CancelSubmit property is set to true a StaticValidator is added for all strings in the ErrorMessages array.
4. Page.Validate is called which triggers all server side validators for the form fields. If the CancelSubmit for the BeforeReadingPostedData event is set to true or the page is not valid the posting is cancelled.
5. Posted data is read and validated.
6. BeforeSubmitPostedData – public event is triggered. If the CancelSubmit property is set to true a StaticValidator is added for all strings in the ErrorMessages array.
7. If the CancelSubmit for the BeforeReadingPostedData event is set to true or the page is not valid the posting is cancelled.
8. The form data is sent. If the user is anonymous a cookie will be set to indicate that the form has been posted.
9. AfterSubmitPostedData – public event is triggered.

XForms Web Controls