ASP.NET MVC - Pass Json String to View using ViewData
The Json() controller method returns a JsonResult, which isn't the same as a JSON string. The JsonResult holds data, but the data is actually written directly to the response when the View Engine calls JsonResult.ExecuteResult(). That's all probably more information than you want there - the point is that calling Json() in a controller won't give you a string of JSON.
If you just want to turn your data into a JSON string, you can use the JavaScriptSerializer, which is what the Json() method uses internally:
JavaScriptSerializer serializer = new JavaScriptSerializer();ViewData["JsonRegionList"] = serializer.Serialize(jsonRegionList);