XML query - retrieving values

Question

To my great frustration, I spent half a day to build some queries for an XML document and I don't know anything more than I knew before I started. So, I'm taking the easy way out and ask again for help.

The XML code is like this:

<?xml version="1.0" ?>
<Main>
<alpha Id = "AlphaId_1">
    <beta>AlphaId1_Beta</beta>
    <gamma>AlphaId1_Gama</gamma>
    <delta Type = "A">AlphaId1_DeltaTypeA</delta>
    <delta Type = "B">AlphaId1_DeltaTypeB</delta>
    <kapa Id="01">
        <description>AlphaId1_KapaId1_Descr</description>
        <name>AlphaId1KapaId1_Name</name>
        <teta>AlphaId1KapaId1_Teta</teta>
    </kapa>
    <kapa Id="02">
        <description>AlphaId1KapaId2_Descr</description>
        <name>AlphaId1KapaId2_Name</name>
        <teta>AlhaId1KapaId2_Teta</teta>
    </kapa>
</alpha>
<alpha Id = "AlphaId_2">
    <beta>AlphaId2_Beta</beta>
    <gamma>AlphaId2_Gama</gamma>
    <delta Type = "A">AlphaId2_DeltaTypeA</delta>
    <delta Type = "B">AlphaId2_DeltaTypeB</delta>
    <kapa Id="01">
        <description>AlphaId2_KapaId1_Descr</description>
        <name>AlphaId2KapaId2_Name</name>
        <teta>AlphaId2KapaId2_Teta</teta>
    </kapa>
    <kapa Id="02">
        <description>AlphaId1KapaId2_Descr</description>
        <name>AlphaId2KapaId2_Name</name>
        <teta>AlhaId2KapaId2_Teta</teta>
    </kapa>
</alpha>
</Main>

I am looking for a query to retrieve for example the value "AlphaId2_DeltaTypeA". The second query should retrieve all the description values from every KapaId for a selected AlphaId.

The only code I could come up with is

XDocument xdoc = XDocument.Load(@"doc.xml");

IEnumerable<XElement> list1 = xdoc.Root.Descendants("delta");

  var cifmi = 
    from el in list1 
    where   (string)el.Attribute("Type") == "A" 
    select el;

    foreach (XElement el in cifmi)
    {
      textBox1.AppendText(el.Value + System.Environment.NewLine);
    }

The code finds two values instead of one.

Answer 1

var xDoc = XDocument.Load("Input.txt");

var alpha = (from a in xDoc.Root.Elements("alpha")
             let deltas = a.Elements("delta")
             let deltaA = deltas.First(x => (string)x.Attribute("Type") == "A")
             where (string)deltaA == "AlphaId2_DeltaTypeA"
             select a).First();

var descriptions = alpha.Elements("kapa")
                        .Select(x => (string)x.Element("description")).ToList();

It will only look for <delta> which has both Type="A" and value of AlphaId2_DeltaTypeA. If you only care about value try that one:

var alpha = (from a in xDoc.Root.Elements("alpha")
             let deltas = a.Elements("delta")
             where deltas.Any(x => (string)x == "AlphaId2_DeltaTypeA")
             select a).First();

Update

*alpha Id == "AlphaId_1" and delta Type = "A" and the answer is AlphaId1_DeltaTypeA*

var alpha = (string)xDoc.Root
                        .Elements("alpha")
                        .First(x => (string)x.Attribute("Id") == "AlphaId_1")
                        .Elements("delta")
                        .First(x => (string)x.Attribute("Type") == "A");