view-data-* attribute for partial tag helper

src/Mvc/Mvc.TagHelpers/src/PartialTagHelper.cs

@@ -28,6 +28,7 @@ public class PartialTagHelper : TagHelper
 
     private readonly ICompositeViewEngine _viewEngine;
     private readonly IViewBufferScope _viewBufferScope;
+    private ViewDataDictionary _viewData;
 
     /// <summary>
     /// Creates a new <see cref="PartialTagHelper"/>.
@@ -91,7 +92,19 @@ public object Model
     /// <summary>
     /// A <see cref="ViewDataDictionary"/> to pass into the partial view.
     /// </summary>
-    public ViewDataDictionary ViewData { get; set; }
+    [HtmlAttributeName("view-data", DictionaryAttributePrefix = "view-data-")]
+    public ViewDataDictionary ViewData
+    {
+        get
+        {
+            if (_viewData == null)
+            {
+                _viewData = new ViewDataDictionary(ViewContext.ViewData);
+            }
+            return _viewData;
+        }
+        set => _viewData = value;
+    }
 
     /// <summary>
     /// Gets the <see cref="Rendering.ViewContext"/> of the executing view.

src/Mvc/test/WebSites/HtmlGenerationWebSite/Areas/Customer/Pages/PartialWithViewData.cshtml

@@ -0,0 +1,13 @@
+@page
+
+@{
+  ViewData["Title"] = "PartialWithViewData";
+}
+
+<div>
+  <partial name="_PrintViewData" view-data-id="123" view-data-returnUrl='"/dashboard"' />
+</div>
+
+<div>
+  <partial name="_PrintViewData" view-data-id="456" view-data-name='"John Doe"' />
+</div>

src/Mvc/test/WebSites/HtmlGenerationWebSite/Areas/Customer/Pages/_PrintViewData.cshtml

@@ -0,0 +1,8 @@
+<h4>ViewData Values</h4>
+<dl>
+  @foreach (var key in ViewData.Keys)
+  {
+    <dt>@key</dt>
+    <dd>@ViewData[key]</dd>
+  }
+</dl>