split text- c# (kelimeleri ayır)

private string KelimeleriAyir(char ayrac,string txt)
{
string[] Kelimeler = txt.Split(ayrac);
StringBuilder sb = new StringBuilder();
foreach (String kelime in Kelimeler)
{
sb.Append(kelime);
}
//MessageBox.Show(sb.ToString() );
return sb.ToString();
}