private void toPowerPointToolStripMenuItem_Click(object sender, EventArgs e) { OpenFileDialog filePicker = new OpenFileDialog(); filePicker.Multiselect = true; DialogResult result = filePicker.ShowDialog(); if (result == DialogResult.OK) // Test result. { List <string> images = filePicker.FileNames.ToList(); // List<string> test = new List<string>( PowerpointExporter test = new PowerpointExporter(); test.ExportToPowerpoint(images); } }