diff --git a/Capnp.Net.Runtime/TypeIdAttribute.cs b/Capnp.Net.Runtime/TypeIdAttribute.cs
new file mode 100644
index 0000000..098dd03
--- /dev/null
+++ b/Capnp.Net.Runtime/TypeIdAttribute.cs
@@ -0,0 +1,27 @@
+using System;
+
+namespace Capnp
+{
+    /// <summary>
+    /// Annotates an enum, class or interface with its schema type identifier.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Enum | AttributeTargets.Class |AttributeTargets.Interface, AllowMultiple = false, Inherited = false)]
+    public class TypeIdAttribute : Attribute
+    {
+        /// <summary>
+        /// Constructs this attribute.
+        /// </summary>
+        /// <param name="typeId">The 64-bit type identifier from the schema file.</param>
+        /// <exception cref="ArgumentOutOfRangeException"><paramref name="typeId"/> is zero.</exception>
+        public TypeIdAttribute(ulong typeId)
+        {
+            if (typeId == 0) throw new ArgumentOutOfRangeException(nameof(typeId), "The value cannot be zero.");
+            Id = typeId;
+        }
+
+        /// <summary>
+        /// The schema type identifier.
+        /// </summary>
+        public ulong Id { get; }
+    }
+}
diff --git a/capnpc-csharp/Generator/CommonSnippetGen.cs b/capnpc-csharp/Generator/CommonSnippetGen.cs
index 56d974e..40a4fa9 100644
--- a/capnpc-csharp/Generator/CommonSnippetGen.cs
+++ b/capnpc-csharp/Generator/CommonSnippetGen.cs
@@ -108,5 +108,19 @@ namespace CapnpC.Generator
                         new[]{
                             Token(SyntaxKind.PublicKeyword),
                             Token(SyntaxKind.ConstKeyword)}));
+
+        public static AttributeSyntax MakeTypeIdAttribute(ulong id) =>
+            Attribute(
+                IdentifierName("TypeId"))
+            .WithArgumentList(
+                AttributeArgumentList(
+                    SingletonSeparatedList<AttributeArgumentSyntax>(
+                        AttributeArgument(HexLiteral(id)))));
+
+        public static SyntaxList<AttributeListSyntax> MakeTypeIdAttributeLists(ulong id) =>
+            SingletonList<AttributeListSyntax>(
+                AttributeList(
+                    SingletonSeparatedList<AttributeSyntax>(
+                        CommonSnippetGen.MakeTypeIdAttribute(id))));
     }
 }