Linq Query to display string from XML in a TextBox

I'm trying to make a Linq query that will retrieve a string value from an XML file and place it in a TextBox. I think I need to use FirstorDefault(), but I can't figure out how to use it properly. Here is what I have at the moment:

var comm = from comment in xdoc.Descendants("string")                   
           where comment.Attribute("id").Value == tagBox.Text
           select comment.Element("comment").Value;

textBox.Text = comm; //Essentially

Basically, my XML file 开发者_StackOverflow社区looks like this:

<root>
    <string id = "STRING_ID1">
        <element1 />
        <comment> Some string </comment>
        ...
    </string>
</root>

In the first code snippet, tagBox refers to another TextBox that has a string in it which was originally pulled from the id attribute of my string element. The idea is to scan the XML for the matching ID, and simply put the value of the comment element in the textBox.

---

Just change

textBox.Text = comm;

to

textBox.Text = comm.FirstOrDefault();

---

Usage of FirstOrDefault would be as follows

var str = (from str in xdoc.Descendants("string")                   
           where str.Attribute("id").Value == tagBox.Text
           select str).FirstOrDefault();

if(str != null)
{
    textBox.Text = str.Element("comment").Value;
}
else
{
    textBox.Text = "";
}