Create Blocklist JSON programmatically in Umbraco

BlockListCreatorService.cs

    /// <summary>
    /// Helper service for creating JSON necessary for creating block list items programatically using Umbraco <see cref="ContentService"/>
    /// </summary>
    /// <remarks>
    /// Based of this: https://github.com/umbraco/UmbracoDocs/blob/e64ec0e5b28b4e5a37b7865691621e45dd82701f/Getting-Started/Backoffice/Property-Editors/Built-in-Property-Editors/Block-List-Editor/index.md
    /// It's intended for simple content
    /// </remarks>
    public class BlockListCreatorService
    {
        /// <summary>
        /// Creates the Block List JSON from the passed in collection of items. Each item needs to have the <see cref="JsonPropertyAttribute"/> that corresponds to the property alias of the element doc type it is based on
        /// </summary>
        /// <typeparam name="T">The type of your item</typeparam>
        /// <param name="items">The collection of items to create</param>
        /// <param name="contentTypeKey">The GUID for the element type (tip: you can look this up in God Mode!)</param>
        /// <param name="settingsData">Optional settings data - defaults to empty settings</param>
        /// <returns>JSON suitable for Block List</returns>
        /// <exception cref="ArgumentNullException">Raised if items are null</exception>
        public string GetBlockListJsonFor<T>(IEnumerable<T> items, Guid contentTypeKey, List<Dictionary<string, string>> settingsData = null) where T : class
        {
            if (items == null)
            {
                throw new ArgumentNullException(nameof(items));
            }

            Blocklist blocklistNew = new Blocklist();  //initialize our new empty model to mimic proper JSON structure
            var contentList = new List<Dictionary<string, string>>();  //initialize empty list where we will add our content items
            var dictionaryUdi = new List<Dictionary<string, string>>(); // this contains content UDIs

            foreach (var item in items)
            {
                var udi = new GuidUdi("element", Guid.NewGuid()).ToString();

                PropertyInfo[] props = item.GetType().GetProperties();

                var propertyValues = new Dictionary<string, string>()
                {
                    { "contentTypeKey", contentTypeKey.ToString() },
                    { "udi", udi.ToString() }
                };

                foreach (PropertyInfo prop in props)
                {
                    object[] attrs = prop.GetCustomAttributes(true);
                    foreach (object attr in attrs)
                    {
                        if (attr is JsonPropertyAttribute attribute)
                        {
                            propertyValues.Add(attribute.PropertyName, prop.GetValue(item)?.ToString() ?? string.Empty);
                        }
                    }
                }

                contentList.Add(propertyValues);

                dictionaryUdi.Add(new Dictionary<string, string> { { "contentUdi", udi } });
            }

            blocklistNew.Layout = new BlockListUdi(dictionaryUdi);
            blocklistNew.ContentData = contentList;  //contentData is a list of our object
            blocklistNew.SettingsData = settingsData ?? new List<Dictionary<string, string>>();

            return JsonConvert.SerializeObject(blocklistNew);
        }

        internal class Blocklist //this class is to mock the correct JSON structure when the object is serialized
        {
            [JsonProperty("layout")]
            public BlockListUdi Layout { get; set; }

            [JsonProperty("contentData")]
            public List<Dictionary<string, string>> ContentData { get; set; }

            [JsonProperty("settingsData")]
            public List<Dictionary<string, string>> SettingsData { get; set; }
        }

        internal class BlockListUdi //this is a subclass which corresponds to the "Umbraco.BlockList" section in JSON
        {
            [JsonProperty("Umbraco.BlockList")]  //we mock the Umbraco.BlockList name with JsonPropertyAttribute to match the requested JSON structure
            public List<Dictionary<string, string>> ContentUdi { get; set; }

            public BlockListUdi(List<Dictionary<string, string>> items)
            {
                this.ContentUdi = items;
            }
        }
    }
    
    // Below is an example class that represents a Block List item. It's for a block list of Location items. 
    // The [JsonProperty] for each item should correspond to your property alias of the corresponding element you are creating.

    public class Location
    {
        [JsonProperty("displayName")]
        public string Name { get; set; }

        [JsonProperty("country")]
        public string Country { get; set; }

        [JsonProperty("address1")]
        public string Address1 { get; set; }

        [JsonProperty("address2")]
        public string Address2 { get; set; }

        [JsonProperty("city")]
        public string City { get; set; }

        [JsonProperty("postCode")]
        public string PostCode { get; set; }
    }
    
    // You would then create a List of Locations ie. List<Location> locations = new List<Location>() and populate the data. You would then get your JSON back as:

   var json = blockListCreatorService.GetBlockListJsonFor(locations, new Guid("07cc06f6-8f16-4a7f-90b9-b04c59bcdf97"));
   
   // The GUID corresponds to the GUID of your block list element in Umbraco. Tip: You can use my God Mode package to find out the Guid easily - https://www.nuget.org/packages/Diplo.GodMode/