C＃XML：System.InvalidOperationException

Question

我一直在用一个项目学习C＃的XML，但是我一直在学习InvalidOperationException。我把代码放在下面

        XmlTextWriter writer = new XmlTextWriter(path, System.Text.Encoding.UTF8);
        writer.WriteStartDocument(true);
        writer.Formatting = Formatting.Indented;
        writer.Indentation = 4;

        writer.WriteStartElement("User Info");
            writer.WriteStartElement("Name");
                writer.WriteString(userName);
            writer.WriteEndElement();
            writer.WriteStartElement("Tutor Name");
                writer.WriteString(tutorName);
            writer.WriteEndElement();
        writer.WriteEndElement();

        writer.WriteStartElement("Course Data"); /*This is where the exception points to*/
            foreach (UserCourse c in courses)
            {
                String cn = c.Name;
                writer.WriteStartElement(cn);

                foreach (UserUnit u in c.Units)
                {
                    writer.WriteStartElement(u.Name.ToString());

                    foreach (UserObjective o in u.Objectives)
                    {
                        writer.WriteStartElement(o.Name.ToString());
                        writer.WriteString(o.Score.ToString());
                        writer.WriteEndElement();
                    }
                    writer.WriteEndElement();
                }
                writer.WriteEndElement();
            }
        writer.WriteEndElement();

        writer.WriteEndDocument();
        writer.Close();

也许有人能看出我做错了什么。我感谢任何帮助！

Answer 1

XML元素名称不能包含空格。

请参阅XML Naming Rules。

你好像应该有一个根元素。与CourseData类似，应位于UserInfo内。

结帐Fiddle

Answer 2

“用户信息”和“课程数据”是不同的实体。如果是这样，我认为你可以将它们封装在一个实体中。

            XmlTextWriter writer = new XmlTextWriter(path, System.Text.Encoding.UTF8);
            writer.WriteStartDocument(true);
            writer.Formatting = Formatting.Indented;
            writer.Indentation = 4;

            writer.WriteStartElement("My Entity"); /* It is a biggest one*/
            writer.WriteStartElement("User Info");
            writer.WriteStartElement("Name");
            writer.WriteString(userName);
            writer.WriteEndElement();
            writer.WriteStartElement("Tutor Name");
            writer.WriteString(tutorName);
            writer.WriteEndElement();
            writer.WriteEndElement();

            writer.WriteStartElement("Course Data"); /*This is where the exception points to*/
            foreach (UserCourse c in courses)
            {
                String cn = c.Name;
                writer.WriteStartElement(cn);

                foreach (UserUnit u in c.Units)
                {
                    writer.WriteStartElement(u.Name.ToString());

                    foreach (UserObjective o in u.Objectives)
                    {
                        writer.WriteStartElement(o.Name.ToString());
                        writer.WriteString(o.Score.ToString());
                        writer.WriteEndElement();
                    }
                    writer.WriteEndElement();
                }
                writer.WriteEndElement();
            }
            writer.WriteEndElement();
            writer.WriteEndElement();

            writer.WriteEndDocument();
            writer.Close();