Prevented Dispose from destroying unmanaged objects we didn't create.

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

src/Generator/Generators/CSharp/CSharpTextTemplate.cs

@@ -1766,6 +1766,21 @@ namespace CppSharp.Generators.CSharp
 
             WriteLine("void Dispose(bool disposing)");
             WriteStartBraceIndent();
+            const string destroyNativeInstance = "DestroyNativeInstance";
+            WriteLine("{0}(false);", destroyNativeInstance);
+            if (hasBaseClass)
+                WriteLine("base.Dispose(disposing);");
+            WriteCloseBraceIndent();
+            NewLine();
+
+            WriteLine("public void {0}()", destroyNativeInstance);
+            WriteStartBraceIndent();
+            WriteLine("{0}(true);", destroyNativeInstance);
+            WriteCloseBraceIndent();
+            NewLine();
+
+            WriteLine("private void {0}(bool force)", destroyNativeInstance);
+            WriteStartBraceIndent();
 
             if (@class.IsRefType)
             {
@@ -1790,7 +1805,8 @@ namespace CppSharp.Generators.CSharp
                     if (!Options.CheckSymbols ||
                         Driver.Symbols.FindLibraryBySymbol(dtor.Mangled, out library))
                     {
-                        WriteLine("Internal.{0}({1});", GetFunctionNativeIdentifier(dtor),
+                        WriteLine("if ({0} || force)", Helpers.OwnsNativeInstanceIdentifier);
+                        WriteLineIndent("Internal.{0}({1});", GetFunctionNativeIdentifier(dtor),
                             Helpers.InstanceIdentifier);
                     }
                 }
@@ -1799,14 +1815,9 @@ namespace CppSharp.Generators.CSharp
             if (@class.IsRefType)
             {
                 WriteLine("if ({0})", Helpers.OwnsNativeInstanceIdentifier);
-                WriteStartBraceIndent();
-                WriteLine("Marshal.FreeHGlobal({0});", Helpers.InstanceIdentifier);
-                WriteCloseBraceIndent();
+                WriteLineIndent("Marshal.FreeHGlobal({0});", Helpers.InstanceIdentifier);
             }
 
-            if (hasBaseClass)
-                WriteLine("base.Dispose(disposing);");
-
             WriteCloseBraceIndent();
             PopBlock(NewLineKind.BeforeNextBlock);
         }

tests/CSharpTemp/CSharpTemp.Tests.cs

@@ -239,4 +239,18 @@ public class CSharpTempTests : GeneratorTestFixture
             Assert.IsFalse(Bar.NativeToManagedMap.ContainsKey(bar.__Instance));
         }
     }
+
+    [Test]
+    public void TestNotDestroyingForeignObjects()
+    {
+        using (var testNativeToManagedMap = new TestNativeToManagedMap())
+        {
+            var hasVirtualDtor2 = testNativeToManagedMap.HasVirtualDtor2;
+            hasVirtualDtor2.Dispose();
+            using (var hasVirtualDtor1 = hasVirtualDtor2.HasVirtualDtor1)
+            {
+                Assert.AreEqual(5, hasVirtualDtor1.TestField);
+            }
+        }
+    }
 }

tests/CSharpTemp/CSharpTemp.cpp

@@ -401,6 +401,11 @@ Foo StructWithPrivateFields::getComplexPrivateField()
     return complexPrivateField;
 }
 
+HasVirtualDtor1::HasVirtualDtor1()
+{
+    testField = 5;
+}
+
 HasVirtualDtor1::~HasVirtualDtor1()
 {
 }

tests/CSharpTemp/CSharpTemp.h

@@ -427,7 +427,9 @@ void TestPointers::TestTripleCharPointers(const char*** names)
 class DLL_API HasVirtualDtor1
 {
 public:
+    HasVirtualDtor1();
     virtual ~HasVirtualDtor1();
+    int testField;
 };
 
 class DLL_API HasVirtualDtor2