c# - LINQ to XML equivalent of XPath -

i have code parses xml looks this:

<custom_fields>   <custom_field>       <column_name>foo</column_name>     <column_value>0</column_value>   <description>submitted</description>     <data_type>boolean</data_type>     <length>0</length>     <decimal>0</decimal>   </custom_field>   <custom_field>     <column_name>bar</column_name>     <column_value>0</column_value>     <description>validated</description>     <data_type>boolean</data_type>     <length>0</length>     <decimal>0</decimal>   </custom_field> </custom_fields> ... more <custom_field> elements... 

i want find element called custom_field has child element called column_name value (for example bar), , find child's sibling called column_value , value. right use xpath on xmldocument this:

string path = "//custom_fields/custom_field[column_name='" + key + "']"; xmlnode xnode = doc.selectsinglenode(path); if (xnode != null) {     xmlnode v = xnode.selectsinglenode("column_value");     val.setvalue(v.innertext); } 

where key name of field looking for.

but want using new linq xml syntax on xdocument. thinking move of old-style xpath parsing linq methods. maybe it's not idea, case if can work, believe have better understanding of linq in general, , able clean lot of complex code.

you can use xpath within linq xml. include system.xml.xpath namespace.

var xpath = string.format("//custom_fields/custom_field[column_name='{0}']/column_value", key); var custom_field = doc.xpathselectelement(xpath); if (custom_field != null) {     val.setvalue((int)custom_field); } 

otherwise equivalent linq xml query:

var custom_field = doc.descendants("custom_fields")                       .elements("custom_field")                       .where(cf => cf.element("column_name").value == key) // assuming `key` string                       .elements("column_value")                       .singleordefault();