Make it possible to add Razor HTML content to the shape as a property

src/OrchardCore.Modules/OrchardCore.Demo/Controllers/HomeController.cs

@@ -104,13 +104,13 @@ public async Task<ActionResult> DisplayShape(string contentItemId)
                 return NotFound();
             }
 
-            var shape = Shape
-                .Foo()
-                .Line(contentItem.As<TestContentPartA>().Line);
+            var shape = await Shape.Foo(Line: contentItem.As<TestContentPartA>().Line);
 
             return View(shape);
         }
 
+        public IActionResult AddProperty() => View();
+
         public ActionResult Raw()
         {
             return View();

src/OrchardCore.Modules/OrchardCore.Demo/Views/EmbedContentInShape.cshtml

@@ -0,0 +1,21 @@
+@using Microsoft.AspNetCore.Html
+
+<div class="border">
+    <p>The content is inserted below this line.</p>
+    <p>@Model.HtmlContent</p>
+    <p>The content is inserted above this line.</p>
+
+    @if (Model.SomeProperty != null)
+    {
+        <p>And here is another property: @Model.SomeProperty.</p>
+    }
+
+    @if (Model.OtherContent is IHtmlContent otherContent)
+    {
+        <div class="border">
+            <p>Another property called "OtherContent" starts here.</p>
+            <p>@otherContent</p>
+            <p>Another property called "OtherContent" ends here.</p>
+        </div>
+    }
+</div>

src/OrchardCore.Modules/OrchardCore.Demo/Views/Home/AddProperty.cshtml

@@ -0,0 +1,23 @@
+@using Microsoft.AspNetCore.Html
+
+<shape type="EmbedContentInShape">
+    <add-property name="HtmlContent">
+        The inner HTML of the <code>&lt;add-property name="propertyName"&gt;</code> tag helper (which is a direct child
+        of the <code>&lt;shape&gt;</code> tag helper) is converted into HTML and then passed to the shape as a model
+        property. The property's name is the string passed into the <code>name</code> attribute.
+        <shape type="TestContentPartA" Line="Sample Data" Creating="Now" Processing="Later"/>
+        Even other shapes can be included!
+    </add-property>
+    <add-property name="OtherContent">
+        You can have multiple, they are just <code>@nameof(IHtmlContent)</code> type shape properties.
+    </add-property>
+    <add-property name="SomeProperty" value="Some value passed to the attribute." />
+</shape>
+
+<shape type="EmbedContentInShape" HtmlContent="This property is ignored.">
+    <add-property name="HtmlContent">
+        If a <code>&lt;add-property&gt;</code> tag helper exists, it takes precedence over any matching attribute of the
+        <code>&lt;shape&gt;</code> tag helper. This is because child tag helpers are evaluated after the shape is
+        created, right before it's displayed.
+    </add-property>
+</shape>

src/OrchardCore/OrchardCore.DisplayManagement/TagHelpers/AddPropertyTagHelper.cs

@@ -0,0 +1,28 @@
+using Microsoft.AspNetCore.Html;
+using Microsoft.AspNetCore.Razor.TagHelpers;
+using System.Threading.Tasks;
+
+namespace OrchardCore.DisplayManagement.TagHelpers;
+
+[HtmlTargetElement("add-property", Attributes = "name", TagStructure = TagStructure.NormalOrSelfClosing)]
+public class AddPropertyTagHelper : TagHelper
+{
+    [HtmlAttributeName("name")]
+    public string Name { get; set; }
+
+    public override async Task ProcessAsync(TagHelperContext context, TagHelperOutput output)
+    {
+        if (string.IsNullOrWhiteSpace(Name))
+        {
+            return;
+        }
+
+        var content = await output.GetChildContentAsync(useCachedResult: false);
+        var shape = (IShape)context.Items[typeof(IShape)];
+        shape.Properties[Name.Trim()] = output.Attributes.ContainsName("value")
+            ? output.Attributes["value"].Value
+            : new HtmlString(content.GetContent());
+
+        output.SuppressOutput();
+    }
+}

src/OrchardCore/OrchardCore.DisplayManagement/TagHelpers/BaseShapeTagHelper.cs

@@ -133,7 +133,7 @@ public override async Task ProcessAsync(TagHelperContext tagHelperContext, TagHe
                 shape.Metadata.Wrappers.Add(Convert.ToString(output.Attributes["wrapper"].Value));
             }
 
-            tagHelperContext.Items.Add(typeof(IShape), shape);
+            tagHelperContext.Items[typeof(IShape)] = shape;
 
             if (!string.IsNullOrWhiteSpace(Cache))
             {

src/docs/reference/core/Placement/README.md

@@ -175,6 +175,26 @@ Metadata tag helper example:
 </menu>
 ```
 
+#### Adding properties with additional tag helpers
+
+Properties can be passed to a shape by adding attributes to the shape tag helper, as mentioned above. But you can also use the `<add-property>` tag helper inside `<shape>`. This even lets you pass Razor code as properties with the `IHtmlContent` value, if you omit the `value` attribute. Something that can't be easily done otherwise.
+
+```xml
+<shape type="MyShape">
+    <add-property name="foo" value="1" />
+    <add-property name="bar" value="a" />
+    <add-property name="content">
+        <h2>Some complicated HTML</h2>
+        <div>
+            You can even include shapes:
+            <shape type="AnotherShape" prop-count="10" />
+        </div>
+    </add-property>
+</shape>
+```
+
+This is the same as `<shape type="MyShape" pro-foo="1" prop-bar="a" prop-content="@someHtmlContentVariable" />` where you'd have to construct `someHtmlContentVariable` separately. Of course, you can mix and match the different formats, for example, to only use `<add-property>` when you want to pass HTML content as property.
+
 ### Date Time shapes
 
 #### `DateTime`

src/docs/releases/2.0.0.md

@@ -620,6 +620,10 @@ A new filter named `supported_cultures` was added to allow you to get a list of
 </ul>
 ```
 
+### Adding properties with additional tag helpers
+
+The new `<add-property>` tag helper can be placed inside the `<shape>` tag helpers to add properties to the shape. This is similar to `prop-*` attributes, but you can also include Razor code as the `IHtmlContent` property value, which was impossible before. See more details [here](../reference/core/Placement/README.md#adding-properties-with-additional-tag-helpers).
+
 ### Sealing Types
 
 Many type commonly used by modules can be `sealed`, which improves runtime performance. While it's not mandatory, we recommend that you consider applying this improvement to your own extensions as well. We've implemented this enhancement in the following pull-requests: