Código:
private void leer_clientes()
{
string buffer;
char[] x={';'};
string[] arr;
string fileName = "clientes.txt";
FileStream stream = new FileStream(fileName, FileMode.Open, FileAccess.Read);
StreamReader reader = new StreamReader(stream);
buffer = reader.ReadLine();
arr = buffer.Split(x);
textBox1.Text = arr[0];
reader.Close();
}
Desde ya gracias.