Archivos con extensión específica

Dim ext() As String = {".txt", ".XML"}
Dim dinfo As DirectoryInfo = New DirectoryInfo("C:\carpeta")
Dim xfiles() As FileInfo = dinfo.GetFiles.Where(Function(f) ext.Contains(f.Extension.ToLower)).ToArray

Ejemplo1:

Dim files() As String = Directory.GetFiles("C:\carpeta").Where(Function(f) f.EndsWith(".txt")).ToArray

Ejemplo2:
Dim xfiles() As FileInfo = New DirectoryInfo("C:\carpeta").GetFiles.Where(Function(f) Regex.IsMatch(f.Name, "\.(txt|mp3|xml)$")).ToArray


fuente
fuente2

Obtener el nombre de la base de datos

Public Function returndb(ByVal conex As String) As String
        Dim data() As String = conex.Split(";")
        Dim db As String = ""
        For Each rd As String In data
            If rd.Contains("atalog") Then
                db = rd.Split("=")(1)
                Exit For
            End If
        Next
        Return db
    End Function

Obtener dato de un nodo xml

Public Function nodo(ByVal archivo As String, ByVal tag As String, ByVal deep As Integer) As String
        Dim sr As New StreamReader(Directory.GetCurrentDirectory & "\" & Form1.sdp & archivo, Encoding.UTF8)
        Dim i As Integer = 0
        Dim dato As String = ""
        Dim linea As String = sr.ReadLine()
        While linea IsNot Nothing
            If linea.Contains(tag) Then
                i += 1
            End If
            If i = deep Then
                dato = linea.Substring(tag.Length, linea.Length - 2 * tag.Length - 1)
                Exit While
            End If
            linea = sr.ReadLine().Trim
        End While
        sr.Close()
        sr.Dispose()
        Return dato
    End Function