With this code when the problem can be solved, at least in my case:

 private void Reemplazar_Punto_Coma_ParaExcel(string Fichero)
        {
            using (StreamWriter fileWrite = new StreamWriter(Fichero + "1"))
            {
                using (StreamReader fielRead = new StreamReader(Fichero))
                {
                    String line;
       
                    while ((line = fielRead.ReadLine()) != null)
                    {
                         if(line.Contains(","))
                         {
                             line = line.Replace(",",".");
                         }
                         fileWrite.WriteLine(line);
                    }
                }
            }

            //aqui se renombrea el archivo temporal
            File.Delete(Fichero);
            File.Move(Fichero + "1", Fichero);
        }