Forbid the disposal of unowned objects and simplified the generated code.

Signed-off-by: Dimitar Dobrev <dpldobrev@yahoo.com>

src/Generator/Generators/CSharp/CSharpTextTemplate.cs

@@ -1475,7 +1475,7 @@ namespace CppSharp.Generators.CSharp
         {
             if (method.IsDestructor)
             {
-                WriteLine("{0}.DestroyNativeInstance();", Helpers.TargetIdentifier);
+                WriteLine("{0}.Dispose(false);", Helpers.TargetIdentifier);
                 return;
             }
 
@@ -1784,11 +1784,14 @@ namespace CppSharp.Generators.CSharp
             if (@class.IsRefType)
             {
                 GenerateClassFinalizer(@class);
+
+                // Only root bases need a Dispose
+                if (ShouldGenerateClassNativeField(@class))
                     GenerateDisposeMethods(@class);
             }
         }
 
-        private void GenerateClassFinalizer(Class @class)
+        private void GenerateClassFinalizer(INamedDecl @class)
         {
             if (!Options.GenerateFinalizers)
                 return;
@@ -1836,21 +1839,9 @@ namespace CppSharp.Generators.CSharp
 
             WriteLine("void Dispose(bool disposing)");
             WriteStartBraceIndent();
-            const string destroyNativeInstance = "DestroyNativeInstance";
+            WriteLine("if (!{0} && disposing)", Helpers.OwnsNativeInstanceIdentifier);
-            WriteLine("{0}(false);", destroyNativeInstance);
+            WriteLineIndent("throw new global::System.InvalidOperationException" +
-            if (hasBaseClass)
+                "(\"Managed instances owned by native code cannot be disposed of.\");");
-                WriteLine("base.Dispose(disposing);");
-            WriteCloseBraceIndent();
-            NewLine();
-
-            WriteLine("public {0} void {1}()", hasBaseClass ? "override" : "virtual", destroyNativeInstance);
-            WriteStartBraceIndent();
-            WriteLine("{0}(true);", destroyNativeInstance);
-            WriteCloseBraceIndent();
-            NewLine();
-
-            WriteLine("private void {0}(bool force)", destroyNativeInstance);
-            WriteStartBraceIndent();
 
             if (@class.IsRefType)
             {
@@ -1878,8 +1869,6 @@ namespace CppSharp.Generators.CSharp
             }
 
             var dtor = @class.Destructors.FirstOrDefault();
-            if (ShouldGenerateClassNativeField(@class))
-            {
             if (dtor != null && dtor.Access != AccessSpecifier.Private &&
                 @class.HasNonTrivialDestructor && !dtor.IsPure)
             {
@@ -1887,24 +1876,14 @@ namespace CppSharp.Generators.CSharp
                 if (!Options.CheckSymbols ||
                     Driver.Symbols.FindLibraryBySymbol(dtor.Mangled, out library))
                 {
-                        WriteLine("if ({0} || force)", Helpers.OwnsNativeInstanceIdentifier);
-
                     if (dtor.IsVirtual)
-                        {
-                            WriteStartBraceIndent();
                         GenerateVirtualFunctionCall(dtor, @class);
-                            WriteCloseBraceIndent();
-                        }
                     else
-                        {
                         GenerateInternalFunctionCall(dtor);
                 }
             }
-                }
 
-                WriteLine("if ({0})", Helpers.OwnsNativeInstanceIdentifier);
+            WriteLine("Marshal.FreeHGlobal({0});", Helpers.InstanceIdentifier);
-                WriteLineIndent("Marshal.FreeHGlobal({0});", Helpers.InstanceIdentifier);
-            }
 
             WriteCloseBraceIndent();
             PopBlock(NewLineKind.BeforeNextBlock);

tests/CSharp/CSharp.Tests.cs

@@ -311,11 +311,10 @@ public class CSharpTests : GeneratorTestFixture
         using (var testNativeToManagedMap = new TestNativeToManagedMap())
         {
             var hasVirtualDtor2 = testNativeToManagedMap.HasVirtualDtor2;
-            hasVirtualDtor2.Dispose();
+            Assert.Catch<InvalidOperationException>(hasVirtualDtor2.Dispose);
-            using (var hasVirtualDtor1 = hasVirtualDtor2.HasVirtualDtor1)
+            var hasVirtualDtor1 = hasVirtualDtor2.HasVirtualDtor1;
-            {
             Assert.AreEqual(5, hasVirtualDtor1.TestField);
-            }
+            Assert.Catch<InvalidOperationException>(hasVirtualDtor1.Dispose);
         }
     }