LINQ to Entities无法识别方法'Int32 Int32（System.String）'方法，并且该方法无法转换为商店表达式

public IEnumerable<CourseNames> GetCourseName(){    var courses = from o in entities.UniversityCourses       select new { o.CourseID, o.CourseName };    return courses.ToList() // now we have in-memory query       .Select(c => new CourseNames()       {          CourseID = Convert.ToInt32(c.CourseID), // OK          CourseName = c.CourseName       });}