Added NativeDataSize property to the ICppMarshal interface.

src/Generator/Generators/CSharp/CSharpTextTemplate.cs

@@ -361,6 +361,12 @@ namespace CppSharp.Generators.CSharp
 
         private void GenerateClassMarshals(Class @class)
         {
+            WriteLine("int CppSharp.Runtime.ICppMarshal.NativeDataSize");
+            WriteStartBraceIndent();
+            WriteLine("get {{ return {0}; }}", @class.Layout.DataSize);
+            WriteCloseBraceIndent();
+            NewLine();
+
             WriteLine("void CppSharp.Runtime.ICppMarshal.MarshalManagedToNative(global::System.IntPtr instance)");
             WriteStartBraceIndent();
             WriteCloseBraceIndent();

src/Runtime/Interfaces.cs

@@ -25,6 +25,11 @@ namespace CppSharp.Runtime
 {
     public interface ICppMarshal
     {
+        /// <summary>
+        /// Gets the native data size for the object.
+        /// </summary>
+        int NativeDataSize { get; }
+
         /// <summary>
         /// Converts the managed data to unmanaged data.
         /// </summary>///