我怎样才能从LINQ中对XAttribute值进行子串

Question

I have some ugly xml(if I could change I would) coming to me that I need to be able to process. I wanted to group by a specific attribute in the XML for further processing. The problem is that some of the attributes have a type="A" and some have type="A1", type="A2", etc. I want all of the elements that have an attribute type value that starts with "A" be grouped together.

This is not working and I don't know what to change to get it to work:

    var result = from ele in xdoc.Descendants(Namespace + "item")
                 let item= ele.Attribute("type").Value.Substring(1,1)
                 group ele by item into grp
                 select grp;

When I take off the substring it works fine, but obviously doesn't group how I want.

Error:

Error has been thrown by the target of an invocation

Example XML:

<items>
 <item type="A" position="0">
   <itemvalue>10</itemvalue>
 </item>
  <item type="A1" position="1">
    <itemvalue>20</itemvalue>
 </item>
  <item type="A2" position="2">
    <itemvalue>30</itemvalue>
 </item>
  <item type="B" position="0">
    <itemvalue>10</itemvalue>
  </item>
   <item type="B1" position="1">
     <itemvalue>20</itemvalue>
  </item>
   <item type="B2" position="2">
     <itemvalue>30</itemvalue>
 </item>
</items>

Answer 1

如果没有我自己编写的编译器并在我的手机上输入，我会说你应该将0作为第一个参数传递给Substring ，即Substring(0,1) 。