Constrained Textbox Element Form Element for EPiserver

ConstrainedTextbox.css

.epi-forms-icon.epi-forms-constrainedtextboxelementblock__icon {
    background-image: url(constrainedtextboxelementblock16x16.png);
}

ConstrainedTextboxElementBlock.ascx

<%@ import namespace="System.Web.Mvc" %>
<%@ import namespace="EPiServer.Web.Mvc.Html" %>
<%@ import namespace="EPiServer.Forms.Core.Models" %>
<%@ import namespace="EPiServer.Forms.Implementation.Elements" %>
<%@ control language="C#" inherits="ViewUserControl<$rootnamespace$.Business.Forms.ConstrainedTextbox.Block.ConstrainedTextboxElementBlock>" %>

<%  var formElement = Model.FormElement; 
    var labelText = Model.Label;
    var maxLength = Model.MaxLength;
%>

<div class="Form__Element FormTextbox" data-epiforms-element-name="<%: formElement.Code %>" >
    <label for="<%: formElement.Guid %>" class="Form__Element__Caption"><%: labelText %></label>
    <input name="<%: formElement.Code %>" id="<%: formElement.Guid %>" type="text" class="FormTextbox__Input" 
        placeholder="<%: Model.PlaceHolder %>" value="<%: Model.PredefinedValue %>"  <%: Html.Raw(formElement.AttributesString) %>
        maxlength="<%: maxLength %>" />

    <span data-epiforms-linked-name="<%: formElement.Code %>" class="Form__Element__ValidationError" style="display: none;">*</span>
</div>

ConstrainedTextboxElementBlock.cs

using System.ComponentModel.DataAnnotations;
using EPiServer.DataAbstraction;
using EPiServer.DataAnnotations;
using EPiServer.Forms.Implementation.Elements;

namespace $rootnamespace$.Business.Forms.ConstrainedTextbox.Block
{
    [ContentType(
        DisplayName = "Constrained Textbox",
        GroupName = "Form Elements",
        GUID = "5445D5A7-965F-45FF-BF49-5633B83F2ECF")]
    public class ConstrainedTextboxElementBlock : TextboxElementBlock
    {
        [Display(
            GroupName = "Forms authoring",
            Order = 1,
            Name = "Max field length",
            Description = "The maximum length of the input field"),
         CultureSpecific]
        public virtual int MaxLength { get; set; }

        public override void SetDefaultValues(ContentType contentType)
        {
            base.SetDefaultValues(contentType);
            MaxLength = 10;
        }
    } 
}

ConstrainedTextboxElementBlockDescriptor.cs

using EPiServer.Forms.EditView;
using EPiServer.Shell;
using $rootnamespace$.Business.Forms.ConstrainedTextbox.Block;

namespace $rootnamespace$.Business.Forms.ConstrainedTextbox.UIDescriptor
{
    [UIDescriptorRegistration]
    public class ConstrainedTextboxElementBlockDescriptor : FormElementBlockDescriptor<ConstrainedTextboxElementBlock>
    {
    }
}

Form-ConstrainedTextBox_EN.xml

<?xml version="1.0" encoding="utf-8" ?>
<languages>
  <language name="English" id="en">
    <contenttypes>
      <constrainedtextboxelementblock>
        <name>Constrained Textbox</name>
      </constrainedtextboxelementblock>
    </contenttypes>
  </language>
</languages>

module.config.transform

<?xml version="1.0" encoding="utf-8"?>
<module>
  <clientResources>
    <add name="Forms" path="~/Business/Forms/ConstrainedTextbox/ClientResources/ConstrainedTextbox.css" resourceType="Style" />
  </clientResources>
</module>

This is the icon that is associated