Umbraco Forms functionality can be extended in different ways. In this section we focus on techniques available to a back-end/C# developer.

For front-end extensions, specifically via theming, see the Themes section.

Developing Custom Providers

Although the Forms package comes with many fields, workflows and other built-in types, you can still create and develop your own if needed.

Many features of Forms use a provider model, which makes it quicker to add new parts to the application.

The model uses the notion that everything must have a type to exist. The type defines the capabilities of the item. For instance a Textfield on a form has a FieldType, this particular field type enables it to render an input field and save text strings. The same goes for workflows, which have a workflow type, datasources which have a datasource type and so on. Using the model you can seamlessly add new types and thereby extend the application.

It is possible to add new Field types, Data Source Types, Prevalue Source Types, Export Types, and Workflow Types.

A field type handles rendering of the UI for a field in a form. It renders a standard ASP.NET webcontrol and is able to return a list of values when the form is saved.

The concept of provider settings, common to the field and other types, is also discussed in this section.

Data Source Types

A data source type enables Umbraco Forms to connect to a custom source of data. A data source consists of any kind of storage if it is possible to return a list of fields Umbraco Forms can map values to. For example: a Database data source can return a list of columns Forms can send data to. This enables Umbraco Forms to map a form to a data source. A data source type is responsible for connecting Forms to external storage.

A prevalue source type connects to 3rd party storage to retrieve values. These values are used on fields supporting prevalues. The source fetches the collection of values.

A workflow can be executed each time a form changes state (when it is submitted for instance). A workflow is responsible for executing logic which can modify the record or notify 3rd party systems.

Export types are responsible for turning form records into any other data format, which is then returned as a file.

Custom magic string format functions to add to the ones shipped with Umbraco Forms can be created in code.

When creating a text field in Umbraco Forms, a validation pattern in the form of a regular expression can be applied. Default patterns can be removed or re-ordered, and custom ones created and added.

Handling Forms Events

Another option for extension via custom code is to hook into one of the many events available.

Form events are raised during the submission life cycle and can be handled for executing custom logic.

When a new form is created, the default behavior is to add a single workflow. This workflow will send a copy of the form to the current backoffice user's email address.

A single "data consent" field will also be added unless it has been disabled via configuration.

It's possible to amend this behavior and change it to fit your needs.

Responding to State Values

In the course of submitting a form, Umbraco Forms will set values in TempData and/or HttpContext.Items, that you can use to customize the website functionality.

Customizing Post-Submission Behavior

Whether displaying a message or redirecting, a developer can customize the page viewed after the form is submitted based on the presence of TempData variables.

One variable with a key of UmbracoFormSubmitted has a value containing the Guid identifier for the submitted form.

A second variable contains the Guid identifier of the record created from the form submission. You can find this using the Forms_Current_Record_id key.

In order to redirect to an external URL rather than a selected page on the Umbraco website, you will need to use a custom workflow. Within this workflow you can set the required redirect URL on the HttpContext.Items dictionary using the key FormsRedirectAfterFormSubmitUrl (defined in the constant Umbraco.Forms.Core.Constants.ItemKeys.RedirectAfterFormSubmitUrl).

For example, using an injected instance of IHttpContextAccessor:

_httpContextAccessor.HttpContext.Items[Constants.ItemKeys.RedirectAfterFormSubmitUrl] = "https://www.umbraco.com";

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