private void button1_Click(object sender, EventArgs e) { String strFileName; //Find the Office document. openFileDialog1.FileName = ""; openFileDialog1.ShowDialog(); strFileName = openFileDialog1.FileName; //If the user does not cancel, open the document. if (strFileName.Length != 0) { Preview preview = new Preview(); FileType ft = new FileType("Ppt Files", "*.Ppt", typeof(PowerPointPreview), null); preview.DoAction(strFileName, ft, this); } }