1var of = new OpenFileDialog();
2
3of.InitialDirectory = cbLaufwerke.Text;
4of.Filter = "all files (*.*)|*.*|txt files (*.txt)|*.txt|html files (*.htm,*.html)|*.htm;*.html";
5of.FilterIndex = 1;
6of.RestoreDirectory = true;
7
8if (of.ShowDialog() == DialogResult.OK)
9{
10    txtBox2.Text = of.FileName;
11}