向此LINQ to XML代码添加条件/过滤器 [英] Adding a condition/filter to this LINQ to XML code
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问题描述
我有这个XML字符串"booms":
I have this XML string of "booms":
<booms>
<boom>
<name>John</name>
<address>New York City</address>
</boom>
<boom>
<name>Daniel</name>
<address>Los Angeles</address>
</boom>
<boom>
<name>Joe</name>
<address>Chicago</address>
</boom>
</booms>
我也有这个LINQ C#代码
I also have this LINQ C# code
//string xmlString = ...;
XDocument document = XDocument.Load(new StringReader(xmlString));
var booms = from boomElement in document.Descendants("boom")
let boolChildren = (from boomElementChild in boomElement.Elements()
select String.Format("{0}: {1}",
boomElementChild.Name.LocalName,
boomElementChild.Value))
select String.Join(Environment.NewLine, boolChildren);
var result = String.Join(Environment.NewLine + Environment.NewLine, booms);
将XML转换为以下字符串:
that turns the XML into this string:
name: John
address: New York City
name: Daniel
address: Los Angeles
name: Joe
address: Chicago
问题:
如何更改LINQ以过滤出满足某些条件的动臂?例如,如何过滤出地址包含"New"的动臂?在这种情况下,将给出字符串:
How can I change the LINQ to filter out booms that satisfy some condition? For example, how can I filter out booms that have an address containing "New"? In this case, this would give the string:
name: John
address: New York City
尽管如此,该代码不应仅限于包含"过滤器.
The code should not be limited to only a "contains" filter though.
推荐答案
如果条件限制为相等.
Dictionary<string, string> conditions = new Dictionary<string, string> { { "name", "John" } };
XDocument document = XDocument.Load(new StringReader(xmlString));
var booms = from boomElement in document.Descendants("boom")
where conditions.All(condition => (string)boomElement.Element(condition.Key) == condition.Value) // Where is used to filter the result
let boomChildren = (from boomElementChild in boomElement.Elements()
select String.Format("{0}: {1}",
boomElementChild.Name.LocalName,
boomElementChild.Value))
select String.Join(Environment.NewLine, boomChildren);
var result = String.Join(Environment.NewLine + Environment.NewLine, booms);
如果不限于等于(包含,等于,<,>),则必须创建一个表示条件的结构.
If it is not limited to equal (contain, equal, <, >) you have to create a structure that will represent the condition.
// I've made Condition an abstract class to super any kind of condition.
// Just derive this class with the condition you want (And, Or, Equal, <=, IsNumber, ...)
public abstract class Condition
{
// A condition is defined by this method. Because a condition is basically: "Does the specified value satisfy the condition?"
public abstract bool Satisfy(string valueToTest);
}
// This is the first example of condition.
// I wanted to make the condition immutable (readonly) not to be able to change them.
// So, all parameters of the condition are set during the construction.
public sealed class EqualCondition : Condition
{
private readonly string value;
public string Value { get { return value; } }
public EqualCondition(string value)
{
this.value = value;
}
public override bool Satisfy(string valueToTest)
{
return value == valueToTest; // Equals condition...
}
}
public sealed class ContainCondition : Condition
{
private readonly string value;
public string Value { get { return value; } }
public ContainCondition(string value)
{
this.value = value;
}
public override bool Satisfy(string valueToTest)
{
return valueToTest.Contains(valueToTest); // Contains condition
}
}
// The dictionary is used to list the conditions applied to each element.
Dictionary<string, Condition> conditions = new Dictionary<string, Condition> { { "name", new EqualCondition("John") } };
XDocument document = XDocument.Load("test.xml");
var booms = from boomElement in document.Descendants("boom")
// The next line check where all conditions are satisfied for the corresponding elements
where conditions.All(condition => condition.Value.Satisfy((string)boomElement.Element(condition.Key)))
let boomChildren = (from boomElementChild in boomElement.Elements()
select String.Format("{0}: {1}",
boomElementChild.Name.LocalName,
boomElementChild.Value))
select String.Join(Environment.NewLine, boomChildren);
var result = String.Join(Environment.NewLine + Environment.NewLine, booms);
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