string Nazev="TriŔko Chevak";

string Nazev="Tričko Chevak";

Encoding win = Encoding.GetEncoding(1250);
Encoding z = Encoding.Default;
byte[] zBytes = z.GetBytes(Nazev);
byte[] isoBytes = Encoding.Convert(z, win, zBytes);
Nazev = win.GetString(isoBytes);