Using a dynamic data source with selector components

In some instances, selector form components may benefit from a dynamic source of data. For example, if you need to enable selection from a list of objects, pages, custom table items, or other volatile data.

Connecting a drop-down list to a dynamic data source

The following example demonstrates how to connect a drop-down list form component to a dynamic data source:

  1. Open your project in Visual Studio.

  2. Create a new form component, and register it in the system.

  3. In the model class:

    1. Inherit from SelectorFormComponent<TProperties>.
    2. Override the IEnumerable<HtmlOptionItem> GetHtmlOptions method and implement your data retrieval logic.
    3. (Optional) Cache the results of the operation.
     using System.Linq;
     using System.Collections.Generic;
     using CMS.DocumentEngine;
     using Kentico.Forms.Web.Mvc;
     using Kentico.Web.Mvc;
     using LearningKit.FormBuilder.FormComponents;
     using LearningKit.FormBuilder.FormComponentProperties;
     [assembly: RegisterFormComponent(CustomDropDownComponent.IDENTIFIER, typeof(CustomDropDownComponent), "Drop-down with custom data", IconClass = "icon-menu")]
     namespace LearningKit.FormBuilder.FormComponents
         public class CustomDropDownComponent : SelectorFormComponent<CustomDropDownComponentProperties>
             public const string IDENTIFIER = "CustomDropDownComponent";
             // Retrieves data to be displayed in the selector
             protected override IEnumerable<HtmlOptionItem> GetHtmlOptions()
                 // Perform data retrieval operations here
                 // The following example retrieves all pages of the 'DancingGoatMvc.Article' page type 
                 // located under the 'Articles' section of the Dancing Goat sample website
                 DocumentQuery query = DocumentHelper.GetDocuments("DancingGoatMvc.Article")
                                     .Path("/Articles/", PathTypeEnum.Children)
                                     .Columns("DocumentName", "DocumentGUID")
                 var sampleData = query.ToList().Select(x => new { Name = x.DocumentName,
                                                                     Guid = x.DocumentGUID.ToString() });
                 // Iterates over retrieved data and transforms it into SelectListItems
                 foreach (var item in sampleData)
                     var listItem = new HtmlOptionItem()
                         Value = item.Guid,
                         Text = item.Name
                     yield return listItem;
  4. In the properties class, inherit from SelectorProperties. Optionally, you can implement additional properties required for further customization.

     using Kentico.Forms.Web.Mvc;
     namespace LearningKit.FormBuilder.FormComponentProperties
         public class CustomDropDownComponentProperties : SelectorProperties
             // Implement any required custom properties here
  5. Create a new _CustomDropDownComponent view under ~/Views/Shared/FormComponents that renders a drop-down list populated with the retrieved data. Use the ToSelectListItems extension method (Kentico.Forms.Web.Mvc namespace) to transform the collection of HtmlOptionItems into SelectListItems.

     @using Kentico.Web.Mvc
     @using Kentico.Forms.Web.Mvc
     @using LearningKit.FormBuilder.FormComponents
     @model CustomDropDownComponent
         var htmlAttributes = ViewData.Kentico().GetEditorHtmlAttributes();
     @* Invoking a Get operation on the component's 'Items' property executes the GetItems method. *@
     @Html.DropDownListFor(x => x.SelectedValue, Model.HtmlOptions.ToSelectListItems(), null, htmlAttributes)

    The SelectedValue and HtmlOptions properties, inherited from SelectorFormComponent<TProperties>, respectively hold the value selected by a user, and the list of items to be displayed in the drop-down list.

The form component dynamically retrieves the specified data when instantiated and populates the corresponding drop-down selector.