Added new DEMO NullableTypesShowcase

samples/nullable_types_showcase/NullableTypesShowcase.dpr

@@ -0,0 +1,55 @@
+program NullableTypesShowcase;
+
+{$APPTYPE CONSOLE}
+
+{$R *.res}
+
+uses
+  System.SysUtils,
+  MVCFramework.Nullables;
+
+
+procedure Main;
+begin
+  var lNullableInt: NullableInt32;
+  Assert(lNullableInt.IsNull);
+  Assert(not lNullableInt.HasValue);
+  Assert(lNullableInt.ValueOrDefault = 0);
+  lNullableInt := 3; // compatible with base type
+  Assert(not lNullableInt.IsNull);
+  Assert(lNullableInt.HasValue);
+  Assert(lNullableInt.ValueOrDefault = 3);
+  Assert(lNullableInt.Value = 3);
+
+  var lVal: Integer;
+  if lNullableInt.TryHasValue(lVal) then
+  begin
+    // work with value...
+    {
+    TryHasValue is a shortcut for the following code:
+    if lNullableInt.HasValue then
+    begin
+      var lVal := lNullableInt.Value;
+      // work with value...
+    end;
+    }
+  end;
+
+  lVal := lNullableInt; // compatible with base type - equivalent to lNullableInt.Value
+  {
+    lNullableInt.Value raises exception if "lNullableInt.IsNull = True"
+  }
+end;
+
+begin
+  try
+    Main;
+  except
+    on E: Exception do
+    begin
+      Writeln(E.ClassName, ': ', E.Message);
+    end;
+  end;
+  Write('Press return to continue');
+  Readln;
+end.