How to select a TabItem based off of it's Header

Question

In my program I have a tabItem that gets selected when a TreeViewItem with an equivalent header is selected.

This is what I curre

Answer 1

Firstly, you have to get the parent node and the number contained in its header:

TreeViewItem parentItem = (TreeViewItem)selectedItem.Parent;
int curNumber = getNumber(parentItem.Header.ToString());

getNumber is a function to retrieve the number from its exact location in the parent node header. You have to tell more about that in order to write a proper function; for the time being, just the basics (it extracts all the numbers in the input string):

private int getNumber(string parentNodeHeader)
{
    int curNumber = 0;

    //Required string-analysis actions
    //Sample functionality: extract all the numbers in the given string
    string outString = "";
    int count = -1;
    do
    {
        count = count + 1;
        Char curChar = Convert.ToChar(parentNodeHeader.Substring(count, 1));
        if (Char.IsNumber(curChar))
        {
            outString = outString + parentNodeHeader.Substring(count, 1);
        }
    } while (count < parentNodeHeader.Length - 1);

    if (outString != "")
    {
        curNumber = Convert.ToInt32(outString);
    }

    return curNumber;
}

And then you have to update the query to account for the new information:

 .OfType<TabItem>().SingleOrDefault(n => n.Header.ToString() == selectedItem.Header.ToString() + curNumber.ToString());

UPDATE

The function above just shows the kind of code I usually rely on; but for simple situations (like the proposed one of getting all the numbers in a string), you might prefer to rely on Regex, as suggested by Viv. You might rely on something on the lines of:

private int getNumber(string parentNodeHeader)
{
    System.Text.RegularExpressions.Match m = System.Text.RegularExpressions.Regex.Match(parentNodeHeader, @"\d+");
    return Convert.ToInt32(m.Value);
}

This function only delivers the first set of consecutive numbers it finds; different result than the function above but enough as a proof of concept (intention of this answer).