Group data from text file

I have a routine where I'm reading a text file into a list in the code below.

I need to modify this so that data is "grouped" based on starting and ending tags.

What I want is to group each xml block into one line
So...
<org.m5.api.v1.Response....         >
    <ErrorCount>0</ErrorCount>
    blah...blah...blah..
</org.m5.api.v1.Response>

Becomes
<org.m5.api.v1.Response><ErrorCount>0</ErrorCount>  blah..</org.m5.api.v1.Response>

        Dim list As New List(Of String)

        ' Open file.txt with the Using statement.
        Using r As StreamReader = New StreamReader("C:\temp\Output.txt")
            ' Store contents in this String.
            Dim line As String

            ' Read first line.
            line = r.ReadLine

            ' Loop over each line in file, While list is Not Nothing.
            Do While (Not line Is Nothing)
                ' Add this line to list.
                list.Add(line)
                'Me.ListBox1.Items.Add(line)
                ' Display to console.
                'Console.WriteLine(line)
                ' Read in the next line.
                line = r.ReadLine
            Loop
        End Using

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