Use a JsonConverter with ElementRef

src/Components/Components/ref/Microsoft.AspNetCore.Components.netstandard2.0.cs

@@ -154,8 +154,6 @@ namespace Microsoft.AspNetCore.Components
     public readonly partial struct ElementReference
     {
         private readonly object _dummy;
-        [System.ComponentModel.EditorBrowsableAttribute(System.ComponentModel.EditorBrowsableState.Never)]
-        public string __internalId { [System.Runtime.CompilerServices.CompilerGeneratedAttribute]get { throw null; } }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
     public readonly partial struct EventCallback

src/Components/Components/src/ElementReference.cs

@@ -2,7 +2,9 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.ComponentModel;
+using System.Globalization;
+using System.Text.Json;
+using System.Text.Json.Serialization;
 using System.Threading;
 
 namespace Microsoft.AspNetCore.Components
@@ -10,25 +12,23 @@ namespace Microsoft.AspNetCore.Components
     /// <summary>
     /// Represents a reference to a rendered element.
     /// </summary>
+    [JsonConverter(typeof(ElementReferenceConverter))]
     public readonly struct ElementReference
     {
         private static long _nextIdForWebAssemblyOnly = 1;
 
         /// <summary>
-        /// Gets a unique identifier for <see cref="ElementRef" />.
+        /// Gets a unique identifier for <see cref="ElementReference" />.
         /// </summary>
         /// <remarks>
         /// The Id is unique at least within the scope of a given user/circuit.
         /// This property is public to support Json serialization and should not be used by user code.
         /// </remarks>
-        [EditorBrowsable(EditorBrowsableState.Never)]
+        internal string Id { get; }
-        public string __internalId { get; }
-
-        internal string Id => __internalId;
 
         private ElementReference(string id)
         {
-            __internalId = id;
+            Id = id;
         }
 
         internal static ElementReference CreateWithUniqueId()
@@ -45,13 +45,45 @@ namespace Microsoft.AspNetCore.Components
                 // fields for ElementRefCaptureId, of which only one would be in use depending
                 // on the platform.
                 var id = Interlocked.Increment(ref _nextIdForWebAssemblyOnly);
-                return id.ToString();
+                return id.ToString(CultureInfo.InvariantCulture);
             }
             else
             {
                 // For remote rendering, it's important not to disclose any cross-user state,
                 // such as the number of IDs that have been assigned.
-                return Guid.NewGuid().ToString("D");
+                return Guid.NewGuid().ToString("D", CultureInfo.InvariantCulture);
+            }
+        }
+
+        private sealed class ElementReferenceConverter : JsonConverter<ElementReference>
+        {
+            private static readonly JsonEncodedText IdProperty = JsonEncodedText.Encode("__internalId");
+
+            public override ElementReference Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+            {
+                string id = null;
+                while (reader.Read() && reader.TokenType != JsonTokenType.EndObject)
+                {
+                    if (reader.ValueTextEquals(IdProperty.EncodedUtf8Bytes))
+                    {
+                        reader.Read();
+                        id = reader.GetString();
+                    }
+                }
+
+                if (id is null)
+                {
+                    throw new JsonException("__internalId is required.");
+                }
+
+                return new ElementReference(id);
+            }
+
+            public override void Write(Utf8JsonWriter writer, ElementReference value, JsonSerializerOptions options)
+            {
+                writer.WriteStartObject();
+                writer.WriteString(IdProperty, value.Id);
+                writer.WriteEndObject();
             }
         }
     }

src/Components/Components/test/ElementReferenceTest.cs

@@ -0,0 +1,70 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Text.Json;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Components
+{
+    public class ElementReferenceTest
+    {
+        [Fact]
+        public void Serializing_Works()
+        {
+            // Arrange
+            var elementReference = ElementReference.CreateWithUniqueId();
+            var expected = $"{{\"__internalId\":\"{elementReference.Id}\"}}";
+
+            // Act
+            var json = JsonSerializer.Serialize(elementReference, JsonSerializerOptionsProvider.Options);
+
+            // Assert
+            Assert.Equal(expected, json);
+        }
+
+        [Fact]
+        public void Deserializing_Works()
+        {
+            // Arrange
+            var id = ElementReference.CreateWithUniqueId().Id;
+            var json = $"{{\"__internalId\":\"{id}\"}}";
+
+            // Act
+            var elementReference = JsonSerializer.Deserialize<ElementReference>(json, JsonSerializerOptionsProvider.Options);
+
+            // Assert
+            Assert.Equal(id, elementReference.Id);
+        }
+
+        [Fact]
+        public void Deserializing_WithFormatting_Works()
+        {
+            // Arrange
+            var id = ElementReference.CreateWithUniqueId().Id;
+            var json =
+@$"{{
+    ""__internalId"": ""{id}""
+}}";
+
+            // Act
+            var elementReference = JsonSerializer.Deserialize<ElementReference>(json, JsonSerializerOptionsProvider.Options);
+
+            // Assert
+            Assert.Equal(id, elementReference.Id);
+        }
+
+        [Fact]
+        public void Deserializing_Throws_IfIdIsNotSpecified()
+        {
+            // Arrange
+            var json = "{\"id\":\"some-value\"}";
+
+            // Act
+            var ex = Assert.Throws<JsonException>(() => JsonSerializer.Deserialize<ElementReference>(json, JsonSerializerOptionsProvider.Options));
+
+            // Assert
+            Assert.Equal("__internalId is required.", ex.Message);
+        }
+    }
+}