无法读取DataSet的xml？ [英] Can't read xml for DataSet?
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问题描述
首先我创建DataSet对象
DataSet ds = new DataSet（）;
然后我加载xmlscheme。
ds.ReadXmlSchema（ C：/ Users / Levan / Dcuments / Visual Studio 2012 / Projects / Crashop / CarLibrary / CarDataSet.xsd）; 它加载很好。我使用数据集可视化器进行调试.Xmlscheme具有以下结构表
汽车（carname（字符串），carnumber（字符串），cardiscription（字符串），CarID（int））。比我尝试loadxml
ds.ReadXml（ C：/ Users / Levan / Documents / Visual Studio 2012 / Projects / Crashop / CarLibrary / CarPark.xml）;
xml文件具有以下结构
<？ xml version = 1.0 standalone = 是 ？ >
< NewDataSet >
< 汽车 >
< carname > BMW < / carname >
< carnumber > AA2935IO < / carnumber >
< cardiscription > 汽车< / cardiscription >
< ; CarID > 1 < / CarID >
< ; / Cars >
< 汽车 >
< carname > Mersedes < / carname >
< carnumber > AA2235IO < / carnumber >
< cardiscription > 好车< / cardiscription >
& CarID > 2 < / CarID >
< / Cars >
< / NewDataSet >
结果没有错误，但空表。
ds.Tables [ 汽车]。行。添加（ BMW， AA2935IO， 好车， 1 ）;
工作正常。但我想知道如何从XML文件中读取。在我使用一切都很好的例子中，我找不到合适的解决方案。
解决方案
至少有几种读取/写入xml数据的方法，例如：
1. Linq to XML [ ^ ]
2. Xml序列化/反序列化 [ ^ ]
基于这个 [ ^ ]我建议创建c ustom类集合如下：
汽车类用于存储单车数据。
public class Car
{
private string sCarName = string .Empty;
private string sCarNumber = string .Empty;
private string sCarDescription = string .Empty;
private int iCarId = 0 ;
// contructor
public Car（ string _CarName， string _CarNumber， string _CarDescription， int _CarId）
{
sCarName = _CarName;
sCarNumber = _CarNumber;
sCarDescription = _CarDescription;
iCarId = _CarId;
}
public string CarName
{
get { return sCarName;}
set {sCarName = value ;}
}
public string CarNumber
{
get { return sCarNumber;}
set {sCarNumber = value ;}
}
public string CarDescription
{
get { return sCarDescription;}
设置 {sCarDescription = value ;}
}
public int CarID
{
get { return iCarId ;}
set {iCarId = value ;}
}
}
汽车类继承自CollectionBase并用于存储汽车列表（类型：汽车）：
public class 汽车：CollectionBase
{
public Car Item（ int index）
{
if （index< 0 || index> List.Count-1）
throw new IndexOutOfRangeException（）;
return （Car）List [index];
}
public Car Add（Car _car）
{
_car.CarID = List.Count + 1 ;
int index = List.Add（_car）;
return （Car）List [index];
}
void 删除（ int index）
{
if （index< 0 || index> List.Count-1）
throw new IndexOutOfRangeException（）;
List.Remove（index）;
}
}
用法：
XDocument xdoc = XDocument.Load（ @ D：\ CarPaark .XML）;
Cars CarPark = new Cars（）; // 汽车集合
// 从xml文档中获取数据
// 创建列表< Car>
var cars = xdoc.Descendants（ Car）
。选择（c = > new Car
（
（ string ）c.Element（ CarName），
（ string ）c。元素（ CarNumber），
（ string ）c。元素（ CarDescript ion），
（ int ）c。元素（ CarID）
））;
// 填充集合：从列表中添加汽车< Car>
foreach （Car c in cars）
{
CarPark.Add（c）;
}
// CarPark已准备就绪，可以访问单车使用Item方法。
Car cr = CarPark.Item（ 0 ）;
cr.CarName = Seat Toledo;
注意：您必须先对xml文件进行一些小的更改才能使用它：
<？ xml version = 1.0 编码 = utf-8 standalone = 是 ？ >
< 汽车 >
< < span class =code-leadattribute> Car >
< CarName > BMW < / CarName >
< CarNumber > AA2935IO < / CarNumber >
< CarDescription > 汽车< < span class =code-leadattribute> / CarDescription >
< CarID > 1 < / CarID >
< / Car >
< Car >
< CarName > Mersedes < / CarName >
< CarNumber > AA2235IO < / CarNumber >
< CarDescription > Nice car < / CarDescription >
< CarID > 2 < / CarID >
< / Car >
< / Cars >
如果要实现保存方法，将所有CarPark数据转储到xml文件中，则必须循环执行汽车收藏：
XDocument xdoc = new XDocumen吨（）;
XElement root = new XElement（ 汽车）;
foreach （Car c CarPark）
{
root。添加（ new XElement（ Car ，
new XElement（ CarName，c.CarName），
new XElement（ CarNumber，c.CarNumber），
new XElement（ CarDescription，c.CarDescription），
new XElement（ CarID，c.CarID）））;
}
xdoc.Add（root）;
xdoc.Save（ @ FullPathToXmlFile.xml）;
First I create DataSet object
DataSet ds = new DataSet();
Then I load xmlscheme.
ds.ReadXmlSchema("C:/Users/Levan/Dcuments/Visual Studio 2012/Projects/Crashop/CarLibrary/CarDataSet.xsd"); It load's fine.I use Dataset visualizer for debugging.Xmlscheme has following structure Table
Cars(carname(string),carnumber(string),cardiscription(string),CarID(int)).Than I try loadxml
ds.ReadXml("C:/Users/Levan/Documents/Visual Studio 2012/Projects/Crashop/CarLibrary/CarPark.xml");
xml file has following structure
<?xml version="1.0" standalone="yes"?>
<NewDataSet>
<Cars>
<carname>BMW</carname>
<carnumber>AA2935IO</carnumber>
<cardiscription>Nice car</cardiscription>
<CarID>1</CarID>
</Cars>
<Cars>
<carname>Mersedes</carname>
<carnumber>AA2235IO</carnumber>
<cardiscription>Nice car</cardiscription>
<CarID>2</CarID>
</Cars>
</NewDataSet>
In result no errors,but empty table.
ds.Tables["Cars"].Rows.Add("BMW","AA2935IO","Nice Car",1);
Works fine.But i want to figure out how to read from XML file.In example which i use everything good and i didn't find appropriate solution for me.
解决方案
There is - at least - few ways to read/write xml data, for example:
1. Linq to XML[^]
2. Xml Serialization/deserialization[^]
Based on this[^] i'd suggest to create custom class collection as follow:
Car class is used to store data about single car.
public class Car { private string sCarName = string.Empty; private string sCarNumber = string.Empty; private string sCarDescription = string.Empty; private int iCarId = 0; //contructor public Car(string _CarName, string _CarNumber, string _CarDescription, int _CarId) { sCarName = _CarName; sCarNumber = _CarNumber; sCarDescription = _CarDescription; iCarId = _CarId; } public string CarName { get{return sCarName;} set{sCarName = value;} } public string CarNumber { get{return sCarNumber;} set{sCarNumber = value;} } public string CarDescription { get{return sCarDescription;} set{sCarDescription = value;} } public int CarID { get{return iCarId;} set{iCarId = value;} } }
Cars class inherits fromCollectionBaseand is used to store list of cars (of type:Car):
public class Cars : CollectionBase { public Car Item(int index) { if(index<0 || index>List.Count-1) throw new IndexOutOfRangeException(); return (Car)List[index]; } public Car Add(Car _car) { _car.CarID = List.Count + 1; int index = List.Add(_car); return (Car)List[index]; } void Remove(int index) { if(index<0 || index>List.Count-1) throw new IndexOutOfRangeException(); List.Remove(index); } }
Usage:
XDocument xdoc = XDocument.Load(@"D:\CarPark.xml"); Cars CarPark = new Cars(); //collection of cars //fetch data from xml document //create List<Car> var cars = xdoc.Descendants("Car") .Select(c=> new Car ( (string)c.Element("CarName"), (string)c.Element("CarNumber"), (string)c.Element("CarDescription"), (int)c.Element("CarID") )); //fill collection: add cars from List<Car> foreach(Car c in cars) { CarPark.Add(c); } //CarPark is ready to use, you can access single car using Item method. Car cr = CarPark.Item(0); cr.CarName = "Seat Toledo";
Note: you have to make some minor changes in xml file before you'll be able to use it:
<?xml version="1.0" encoding="utf-8" standalone="yes"?> <Cars> <Car> <CarName>BMW</CarName> <CarNumber>AA2935IO</CarNumber> <CarDescription>Nice car</CarDescription> <CarID>1</CarID> </Car> <Car> <CarName>Mersedes</CarName> <CarNumber>AA2235IO</CarNumber> <CarDescription>Nice car</CarDescription> <CarID>2</CarID> </Car> </Cars>
If you want to implementSavemethod, which will dump allCarParkdata into xml file, you have to loop through the collection of Cars:
XDocument xdoc = new XDocument(); XElement root = new XElement("Cars"); foreach(Car c in CarPark) { root.Add(new XElement("Car", new XElement("CarName", c.CarName), new XElement("CarNumber", c.CarNumber), new XElement("CarDescription", c.CarDescription), new XElement("CarID", c.CarID))); } xdoc.Add(root); xdoc.Save(@"FullPathToXmlFile.xml");
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