通过c的磁通量方向是向下还是向上,为什么?

发布网友 发布时间：2022-05-19 13:59

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懂视网 时间：2022-05-19 18:20

<?xml version="1.0" encoding="iso-8859-1"?> 
<bookstore> 

<book id="1" category="CHILDREN"> 
<title>Harry Potter</title> 
<author>J K. Rowling</author> 
<publishDate>2005-08-15</publishDate> 
<price>29.99</price> 
</book> 

<book id="2" category="WEB"> 
<title>Learning XML</title> 
<author>Erik T. Ray</author> 
<publishDate>2003-10-18</publishDate> 
<price>39.95</price> 
</book> 

</bookstore> 
 
方法1：使用StringBuilder拼接XML 
 代码如下:

/// <summary> 
/// 创建图书信息XML 
/// </summary> 
public void CreateBookXML(string fileName) 
{ 
StringBuilder xmlResult = new StringBuilder("<?xml version="1.0" encoding="utf-8"?>"); 
List<BookInfo> bookList = GetBookList(); //获取图书列表 
if (bookList != null && bookList.Count > 0) 
{ 
xmlResult.Append("<bookstore>"); 
foreach (BookInfo book in bookList) 
{ 
xmlResult.AppendFormat("<book id="{0}" category="{1}">", book.BookId, book.Category); 
xmlResult.AppendFormat("<title>{0}</title>", book.Title); 
xmlResult.AppendFormat("<author>{0}</author>", book.Author); 
xmlResult.AppendFormat("<publishDate>{0}</publishDate>", book.PublishDate.ToString("yyyy-MM-dd")); 
xmlResult.AppendFormat("<price>{0}</price>", book.Price); 
xmlResult.Append("</book>"); 
} 
xmlResult.Append("</bookstore>"); 
} 

//写入文件 
try 
{ 
//1.创建文件流 
FileStream fileStream = new FileStream(fileName, FileMode.Create); 
//2.创建写入器 
StreamWriter streamWriter = new StreamWriter(fileStream); 
//3.将内容写入文件 
streamWriter.WriteLine(xmlResult); 
//4.关闭写入器 
streamWriter.Close(); 
//5.关闭文件流 
fileStream.Close(); 
} 
catch (Exception e) 
{ } 
} 
 
方法2：使用XmlTextWriter类创建XML 
 代码如下:

/// <summary> 
/// 创建图书信息XML 
/// </summary> 
/// <param name="fileName"></param> 
public void CreateBookXML(string fileName) 
{ 
try 
{ 
FileStream fileStream = new FileStream(fileName, FileMode.Create); 
XmlTextWriter writer = new XmlTextWriter(fileStream, Encoding.UTF8); 
List<BookInfo> bookList = GetBookList(); //获取图书列表 
if (bookList != null && bookList.Count > 0) 
{ 
writer.WriteStartDocument(); 
writer.WriteStartElement("bookstore"); //创建父节点 
foreach (BookInfo book in bookList) 
{ 
writer.WriteStartElement("book"); //创建子节点 
writer.WriteAttributeString("id", book.BookId.ToString()); //添加属性 
writer.WriteAttributeString("category", book.Category); 
//图书名称节点 
writer.WriteStartElement("title"); 
writer.WriteValue(book.Title); //节点赋值 
writer.WriteEndElement(); 
//图书作者节点 
writer.WriteStartElement("author"); 
writer.WriteValue(book.Author); 
writer.WriteEndElement(); 
//出版时间节点 
writer.WriteStartElement("publishDate"); 
writer.WriteValue(book.PublishDate.ToString("yyyy-MM-dd")); 
writer.WriteEndElement(); 
//销售价格节点 
writer.WriteStartElement("price"); 
writer.WriteValue(book.Price); 
writer.WriteEndElement(); 

writer.WriteEndElement(); //子节点结束 
} 
writer.WriteEndElement(); //父节点结束 
} 
writer.WriteEndDocument(); 
writer.Close(); 
fileStream.Close(); 
} 
catch (Exception e) 
{ } 
} 
 
XmlTextWriter类：表示提供快速、非缓存、只进方法的编写器，该方法生成包含 XML 数据的流或文件。 
WriteStartDocument()方法：编写XML的声明。 
WriteEndDocument()方法：关闭任何打开的元素或属性并将编写器重新设置为 Start 状态。 
WriteStartElement(string localName)方法：创建一个节点的开始。 
WriteAttributeString(string localName, string value)方法：给节点添加属性。 
WriteValue(value)方法：给节点赋值。 

3、其他代码 

3.1 获取图书列表 
 代码如下:

/// <summary> 
/// 获取图书列表 
/// </summary> 
/// <returns></returns> 
public List<BookInfo> GetBookList() 
{ 
List<BookInfo> bookList = new List<BookInfo>(); 
BookInfo book1 = new BookInfo() { 
BookId = 1, 
Category = "CHILDREN", 
Title = "Harry Potter", 
Author = "J K. Rowling", 
PublishDate = new DateTime(2005,08,15), 
Price = 29.99 
}; 
bookList.Add(book1); 
BookInfo book2 = new BookInfo() 
{ 
BookId = 2, 
Category = "WEB", 
Title = "Learning XML", 
Author = "Erik T. Ray", 
PublishDate = new DateTime(2003,10,18), 
Price = 39.95 
}; 
bookList.Add(book2); 
return bookList; 
} 
 
3.2 图书信息实体类 
 代码如下:

/// <summary> 
/// 图书信息实体类 
/// </summary> 
public class BookInfo 
{ 
public int BookId { set; get; } //图书ID 
public string Title { set; get; } //图书名称 
public string Category { set; get; } //图书分类 
public string Author { set; get; } //图书作者 
public DateTime PublishDate { set; get; } //出版时间 
public Double Price { set; get; } //销售价格 
} 

  
  




                                        

                        
                        热心网友
                        时间：2022-05-19 15:28
                    
                    解析：右边开关闭合后，通过左边线圈C的磁通量方向向下！
说明：磁通量方向也就是穿过闭合线圈C的磁感线方向！