Adds <our-fallback>

From last weeks Umbraco Discord MOB programming Hacktoberfest session

Author: Warren Buckley

Our.Umbraco.TagHelpers/OurFallbackTagHelper.cs

@@ -0,0 +1,63 @@
+using Microsoft.AspNetCore.Mvc.Rendering;
+using Microsoft.AspNetCore.Mvc.ViewFeatures;
+using Microsoft.AspNetCore.Razor.TagHelpers;
+using Umbraco.Cms.Core.Models.PublishedContent;
+using Umbraco.Extensions;
+
+namespace Our.Umbraco.TagHelpers
+{
+    /// <summary>
+    /// Use to fallback simple properties 
+    /// </summary>
+    [HtmlTargetElement("our-fallback")]
+    public class OurFallbackTagHelper : TagHelper
+    {
+        [HtmlAttributeName("property")]
+        public ModelExpression ModelProperty { get; set; }
+
+        [HtmlAttributeName("mode")]
+        public Fallback Mode { get; set; }
+
+        [HtmlAttributeName("culture")]
+        public string CultureCode { get; set; } = null;
+
+        [HtmlAttributeNotBound]
+        [ViewContext]
+        public ViewContext ViewContext { get; set; }
+
+        public override void Process(TagHelperContext context, TagHelperOutput output)
+        {
+            // Check to see that the Model Property is NOT a complex type or a collection of things
+            var isComplexType = ModelProperty.ModelExplorer.Metadata.IsComplexType;
+            var isEnumerableType = ModelProperty.ModelExplorer.Metadata.IsEnumerableType;
+
+            // Only can support simpler things such as strings (as if collection)
+            // We have no way of knowing how they want to iterate and display that HTML etc
+            if(isComplexType || isEnumerableType)
+            {
+                output.SuppressOutput();
+                return;
+            }
+
+            // Attempt to fetch/cast the Model as IPublishedContent
+            var contentNode = ViewContext.ViewData.Model as IPublishedContent;
+            if(contentNode == null)
+            {
+                output.SuppressOutput();
+                return;
+            }
+
+            output.TagName = ""; // Remove the outer <our-fallback>
+
+            // Get the Model property with fallback mode
+            var result = contentNode.Value(ModelProperty.Name, fallback: Mode, culture: CultureCode);
+
+            // If we have a value that can be
+            if (string.IsNullOrWhiteSpace($"{result}") == false)
+            {
+                output.Content.SetHtmlContent($"{result}");
+                return;
+            }
+        }
+    }
+}