Remove duplicate from string function

Function rduplicatestring(ByVal str As String) As String
        rduplicatestring = ""
        Dim myarr() As String = Split(str, Space(1))
        myarr = myarr.Distinct().ToArray
        myarr = myarr.DefaultIfEmpty().ToArray
        rduplicatestring = Replace(Join(myarr, Space(1)), Space(2), Space(1))
        Return rduplicatestring
    End Function