XML read write ('System.Xml.XmlException is thrown)
本文关键字：XmlException Xml is thrown System write read XML | 更新日期: 2023-09-27 18:28:39
class Customers
{
public int CustId { get; set; }
public string Name { get; set; }
public long MobileNo { get; set; }
public string Location { get; set; }
public string Address { get; set; }
StringWriter stringWriter = new StringWriter();
// UserInput
public void InsertCustomer()
{
Console.WriteLine("Enter Your Id");
CustId = int.Parse(Console.ReadLine());
Console.WriteLine("Enter Your Name");
Name = Console.ReadLine();
Console.WriteLine("Enter Your Mobile No");
MobileNo = long.Parse(Console.ReadLine());
Console.WriteLine("Enter Your Location");
Location = Console.ReadLine();
Console.WriteLine("Enter Your Address");
Address = Console.ReadLine();
try
{
XmlDocument doc = new XmlDocument();
doc.Load(@"CustomersDetail.xml");
if (doc.ChildNodes.Count == 0)
{
// It is empty
XDocument xDoc =
new XDocument(
new XDeclaration("1.0", "utf-8", "yes"),
new XComment("LINQ To XML Demo"),
new XElement("Customers",
new XElement("Customer",
new XElement("CustId", CustId),
new XElement("Name", Name),
new XElement("MobileNo", MobileNo),
new XElement("Location", Location),
new XElement("Address", Address))));
xDoc.Save(stringWriter);
xDoc.Save(@"CustomersDetail.xml");
Console.WriteLine("'n Created new XML 'n" + stringWriter);
}
else if (doc.ChildNodes.Count > 1)
{
//if (xDoc.ChildNodes.Count > 1)
// There are more children on the **root level** of the DOM
XDocument xdoc = XDocument.Load(@"CustomersDetail.xml");
xdoc.Element("Customers").Add(
new XElement("Customer",
new XElement("CustId", CustId),
new XElement("Name", Name),
new XElement("MobileNo", MobileNo),
new XElement("Location", Location),
new XElement("Address", Address)));
xdoc.Save(stringWriter);
xdoc.Save(@"CustomersDetail.xml");
Console.WriteLine("'n Added 'n" + stringWriter);
}
}
catch(XmlException exc)
{
//invalid file
Console.WriteLine("Sorry");
}
}
}
我正在尝试创建 XML 数据库
StringWriter stringWriter = new StringWriter();
XDocument xDoc =
new XDocument(
new XDeclaration("1.0", "utf-8", "yes"),
new XComment("LINQ To XML Demo"),
new XElement("Customers",
new XElement("Customer",
new XElement("CustId", CustId),
new XElement("Name", Name),
new XElement("MobileNo", MobileNo),
new XElement("Location", Location),
new XElement("Address", Address))));
xDoc.Save(stringWriter);
xDoc.Save(@"CustomersDetail.xml");
Console.WriteLine("'n Created new XML 'n" + stringWriter);
运行这段代码工作，但重新运行代码会丢失我以前的数据和新数据。
然后是用于在现有 XML 上添加新数据的新代码
XDocument xdoc = XDocument.Load(@"CustomersDetail.xml");
xdoc.Element("Customers").Add(
new XElement("Customer",
new XElement("CustId", CustId),
new XElement("Name", Name),
new XElement("MobileNo", MobileNo),
new XElement("Location", Location),
new XElement("Address", Address)));
xdoc.Save(stringWriter);
xdoc.Save(@"CustomersDetail.xml");
Console.WriteLine("'n Added 'n" + stringWriter);
但运行此代码
XDocument xdoc = XDocument.Load(@"CustomersDetail.xml"(;
System.XML 中发生了类型为"System.Xml.XmlException"的未处理异常.dll
其他信息：缺少根元素。
帮帮我
你在这里有几个问题：
-
您正在加载到
XmlDocument中，然后加载到XDocument中。 没有理由这样做。 选择一个，最好是后者。 -
您调用
doc.Load(@"CustomersDetail.xml");但没有捕获引发的任何异常。 如果该文件不存在，此方法将抛出FileNotFoundException。 (我注意到文档没有明确说明这一点。 这似乎是Microsoft的疏忽。 此外，如果在程序的早期运行中，向"CustomersDetail.xml"写入了无效的 XML，则对doc.Load()的后续调用将引发XmlException。 (例如，空文件是无效的 XML。 所以你可能也想抓住它。 -
在
XmlDocument中，要检查根节点是否已创建，请检查XmlDocument.DocumentElement是否null。 在XDocument中，检查XDocument.Root是否null。 -
您应该将用户界面方法与"保存"方法分开，并消除重复的内联硬编码字符串，如
@"CustomersDetail.xml"。 -
在
InsertCustomer()中，long.Parse()可以抛出各种错误的用户输入异常。 应考虑处理这些异常。
因此：
class Customers
{
public int CustId { get; set; }
public string Name { get; set; }
public long MobileNo { get; set; }
public string Location { get; set; }
public string Address { get; set; }
internal const string XmlFileName = @"CustomersDetail.xml";
private void AddToDB()
{
XDocument xdoc;
if (!XDocumentExtensions.TryLoad(XmlFileName, out xdoc))
// File does not exist. Create it.
xdoc = new XDocument(
new XDeclaration("1.0", "utf-8", "yes"),
new XComment("LINQ To XML Demo"));
if (xdoc.Root == null)
xdoc.Add(new XElement("Customers"));
xdoc.Root.Add(new XElement("Customer",
new XElement("CustId", CustId),
new XElement("Name", Name),
new XElement("MobileNo", MobileNo),
new XElement("Location", Location),
new XElement("Address", Address)));
try
{
xdoc.Save(XmlFileName);
Console.WriteLine("'n Added 'n" + xdoc.ToString());
}
catch (Exception ex)
{
// No documented specific exception types from XDocument.Save() either.
Debug.WriteLine(ex);
Console.WriteLine(string.Format("Failed to write to XML file {0}", XmlFileName));
}
}
// UserInput
public void InsertCustomer()
{
Console.WriteLine("Enter Your Id");
CustId = int.Parse(Console.ReadLine());
Console.WriteLine("Enter Your Name");
Name = Console.ReadLine();
Console.WriteLine("Enter Your Mobile No");
MobileNo = long.Parse(Console.ReadLine());
Console.WriteLine("Enter Your Location");
Location = Console.ReadLine();
Console.WriteLine("Enter Your Address");
Address = Console.ReadLine();
AddToDB();
}
}
用
public static class XDocumentExtensions
{
public static bool TryLoad(string fileName, out XDocument doc)
{
try
{
doc = XDocument.Load(fileName);
return true;
}
catch (FileNotFoundException)
{
// File does not exist yet, so we must create it.
doc = null;
}
catch (Exception ex)
{
// Some other internal error.
// XDocument.Load() has no documented specific exception types :(
// http://stackoverflow.com/questions/6904907/xdocument-loadxmlreader-possible-exceptions
// So we could either catch these or pass them upwards.
System.Diagnostics.Debug.WriteLine(ex);
doc = null;
}
return false;
}
}