I have a simple XML file:
<?xml version="1.0" encoding="utf-8"?>
<ConvenioValidacao>
<convenio ven_codigo="1" tipoValidacao="CPF"></convenio>
<convenio ven_codigo="1" tipoValidacao="MATRICULA"></convenio>
<convenio ven_codigo="3" tipoValidacao="CPF"></convenio>
<convenio ven_codigo="4" tipoValidacao="CPF"></convenio>
</ConvenioValidacao>
I'm trying to do a simple query against this xml file using Linq to XML , here is what i'm doing:
var myXmlDoc = XElement.Load(filePath);
var result = from convenio in myXmlDoc.Element("ConvenioValidacao").Elements("convenio")
where (string)convenio.Attribute("ven_codigo") == "1" &&
(string)convenio.Attribute("tipoValidacao") == "CPF"
select convenio;
It is not working, I'm getting null reference exception.
What I'm doing wrong?
Use this instead:
var result = from convenio in myXmlDoc.Elements("convenio")
where (string)convenio.Attribute("ven_codigo") == "1" &&
(string)convenio.Attribute("tipoValidacao") == "CPF"
select convenio;
Since myXmlDoc
is of type XElement
there is no "document element" and as such the root of the element is the root node ( <ConveioValidacao>
). Since this is the root node you don't need to specify it in an Elements
method since that is current position in document.
As a side note, I recommend that you rename myXmlDoc
to myXmlElement
to reduce confusion.
.Element方法获取给定元素的第一个子元素,在这里ConveioValidacao不是子元素,它是父元素,当你通过XEelemnt.Load()方法加载时,它获取ConveioValidacao及其子元素,所以你应该使用Andrew的码。
Try Descendants instead of Elements
var result = from convenio in myXmlDoc.Descendants("ConveioValidacao").Descendants("convenio")
where (string)convenio.Attribute("ven_codigo") == "1" &&
(string)convenio.Attribute("tipoValidacao") == "CPF"
select convenio;
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