Question

I got this XML file:

<Msg UserText="start 0">
</Msg>
<Msg UserText="A">
</Msg>
<Msg UserText="A">
</Msg>
<Msg UserText="start 1">
</Msg>
<Msg UserText="A">
</Msg>
<Msg UserText="start 2">
</Msg>
<Msg UserText="A">
</Msg>
<Msg UserText="A">
</Msg>
<Msg UserText="A">
</Msg>

I need to count How many ‘A’s are between each “start x”

i.e. for the above i would output:

start 0 : 2 
start 1 : 1 
start 2 : 3

How should i go about this in C# ? i had a few directions but I’m sure there are easier ones out there (e.g. using linq)

Answer 1

Here is a grouping sample:

XDocument doc = XDocument.Load("../../XMLFile1.xml");

var groups = from msg in doc.Root.Elements("Msg")
             where !((string)msg.Attribute("UserText")).StartsWith("start")
             group msg by 
             msg.ElementsBeforeSelf("Msg").Where(m => 
                 ((string)m.Attribute("UserText")).StartsWith("start")).Last();

foreach (var group in groups)
{
    Console.WriteLine("Group starting with {0} has {1} member(s).", 
        group.Key.Attribute("UserText"), group.Count());
}

With the XML input sample XMLFile1.xml being

<Root>
  <Msg UserText="start 0">
  </Msg>
  <Msg UserText="A">
  </Msg>
  <Msg UserText="A">
  </Msg>
  <Msg UserText="start 1">
  </Msg>
  <Msg UserText="A">
  </Msg>
  <Msg UserText="start 2">
  </Msg>
  <Msg UserText="A">
  </Msg>
  <Msg UserText="A">
  </Msg>
  <Msg UserText="A">
  </Msg>
</Root>

I get the output

Group starting with UserText="start 0" has 2 member(s).
Group starting with UserText="start 1" has 1 member(s).
Group starting with UserText="start 2" has 3 member(s).