diff --git a/src/Microsoft.AspNetCore.Razor.Language/DefaultRazorCSharpDocument.cs b/src/Microsoft.AspNetCore.Razor.Language/DefaultRazorCSharpDocument.cs
new file mode 100644
index 0000000000..299b22b96c
--- /dev/null
+++ b/src/Microsoft.AspNetCore.Razor.Language/DefaultRazorCSharpDocument.cs
@@ -0,0 +1,36 @@
+// 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.Collections.Generic;
+
+namespace Microsoft.AspNetCore.Razor.Language
+{
+    internal class DefaultRazorCSharpDocument : RazorCSharpDocument
+    {
+        private readonly string _generatedCode;
+        private readonly RazorDiagnostic[] _diagnostics;
+        private readonly LineMapping[] _lineMappings;
+
+        public DefaultRazorCSharpDocument(
+            string generatedCode,
+            RazorDiagnostic[] diagnostics,
+            LineMapping[] lineMappings)
+        {
+            if (generatedCode == null)
+            {
+                throw new ArgumentNullException(nameof(generatedCode));
+            }
+
+            _generatedCode = generatedCode;
+            _diagnostics = diagnostics ?? Array.Empty<RazorDiagnostic>();
+            _lineMappings = lineMappings ?? Array.Empty<LineMapping>();
+        }
+
+        public override IReadOnlyList<RazorDiagnostic> Diagnostics => _diagnostics;
+
+        public override string GeneratedCode => _generatedCode;
+
+        public override IReadOnlyList<LineMapping> LineMappings => _lineMappings;
+    }
+}
diff --git a/src/Microsoft.AspNetCore.Razor.Language/DefaultRazorCSharpLoweringPhase.cs b/src/Microsoft.AspNetCore.Razor.Language/DefaultRazorCSharpLoweringPhase.cs
index 95503f8fae..1634405947 100644
--- a/src/Microsoft.AspNetCore.Razor.Language/DefaultRazorCSharpLoweringPhase.cs
+++ b/src/Microsoft.AspNetCore.Razor.Language/DefaultRazorCSharpLoweringPhase.cs
@@ -68,13 +68,10 @@ namespace Microsoft.AspNetCore.Razor.Language
             }
             diagnostics.AddRange(renderingContext.Diagnostics);
 
-            var csharpDocument = new RazorCSharpDocument()
-            {
-                GeneratedCode = renderingContext.Writer.GenerateCode(),
-                LineMappings = renderingContext.LineMappings,
-                Diagnostics = diagnostics
-            };
-
+            var csharpDocument = RazorCSharpDocument.Create(
+                renderingContext.Writer.GenerateCode(),
+                diagnostics,
+                renderingContext.LineMappings);
             codeDocument.SetCSharpDocument(csharpDocument);
         }
     }
diff --git a/src/Microsoft.AspNetCore.Razor.Language/RazorCSharpDocument.cs b/src/Microsoft.AspNetCore.Razor.Language/RazorCSharpDocument.cs
index 37d973bc25..f2981dfae8 100644
--- a/src/Microsoft.AspNetCore.Razor.Language/RazorCSharpDocument.cs
+++ b/src/Microsoft.AspNetCore.Razor.Language/RazorCSharpDocument.cs
@@ -1,16 +1,56 @@
 // 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.Collections.Generic;
+using System.Linq;
 
 namespace Microsoft.AspNetCore.Razor.Language
 {
-    public class RazorCSharpDocument
+    public abstract class RazorCSharpDocument
     {
-        public string GeneratedCode { get; set; }
+        public abstract string GeneratedCode { get; }
 
-        public IReadOnlyList<LineMapping> LineMappings { get; set; }
+        public abstract IReadOnlyList<LineMapping> LineMappings { get; }
 
-        public IReadOnlyList<RazorDiagnostic> Diagnostics { get; set; }
+        public abstract IReadOnlyList<RazorDiagnostic> Diagnostics { get; }
+
+        public static RazorCSharpDocument Create(string generatedCode, IEnumerable<RazorDiagnostic> diagnostics)
+        {
+            if (generatedCode == null)
+            {
+                throw new ArgumentNullException(nameof(generatedCode));
+            }
+
+            if (diagnostics == null)
+            {
+                throw new ArgumentNullException(nameof(diagnostics));
+            }
+
+            return new DefaultRazorCSharpDocument(generatedCode, diagnostics.ToArray(), lineMappings: null);
+        }
+
+        public static RazorCSharpDocument Create(
+            string generatedCode,
+            IEnumerable<RazorDiagnostic> diagnostics,
+            IEnumerable<LineMapping> lineMappings)
+        {
+            if (generatedCode == null)
+            {
+                throw new ArgumentNullException(nameof(generatedCode));
+            }
+
+            if (diagnostics == null)
+            {
+                throw new ArgumentNullException(nameof(diagnostics));
+            }
+
+            if (lineMappings == null)
+            {
+                throw new ArgumentNullException(nameof(lineMappings));
+            }
+
+            return new DefaultRazorCSharpDocument(generatedCode, diagnostics.ToArray(), lineMappings.ToArray());
+        }
     }
 }
diff --git a/test/Microsoft.AspNetCore.Razor.Language.Test/RazorCodeDocumentExtensionsTest.cs b/test/Microsoft.AspNetCore.Razor.Language.Test/RazorCodeDocumentExtensionsTest.cs
index 886cb43e07..ce2576d37d 100644
--- a/test/Microsoft.AspNetCore.Razor.Language.Test/RazorCodeDocumentExtensionsTest.cs
+++ b/test/Microsoft.AspNetCore.Razor.Language.Test/RazorCodeDocumentExtensionsTest.cs
@@ -1,6 +1,7 @@
 // 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 Microsoft.AspNetCore.Razor.Language.Intermediate;
 using Xunit;
 
@@ -92,7 +93,7 @@ namespace Microsoft.AspNetCore.Razor.Language
             // Arrange
             var codeDocument = TestRazorCodeDocument.CreateEmpty();
 
-            var expected = new RazorCSharpDocument();
+            var expected = RazorCSharpDocument.Create("", Array.Empty<RazorDiagnostic>());
             codeDocument.Items[typeof(RazorCSharpDocument)] = expected;
 
             // Act
@@ -108,7 +109,7 @@ namespace Microsoft.AspNetCore.Razor.Language
             // Arrange
             var codeDocument = TestRazorCodeDocument.CreateEmpty();
 
-            var expected = new RazorCSharpDocument();
+            var expected = RazorCSharpDocument.Create("", Array.Empty<RazorDiagnostic>());
 
             // Act
             codeDocument.SetCSharpDocument(expected);