Follow this step: 1.You can download Windows® API Code Pack for Microsoft® .NET Framework 2.See how the "\Windows API Code Pack 1.1\source\WindowsAPICodePack\Shell\CommonFileDialogs\CommonFileDialog.cs" make use of IFileDialogCustomize from com. 3.If you want to add a stuff to the "Open" dropdownlist, you can write code below

customize.EnableOpenDropDown(0);

customize.AddControlItem(0, 0, "Open as XXX");

customize.AddControlItem(0, 1, "Open in YYY");

Note: 0 is the Open Button ID After user selected, you can get the selectedIndex through

this.customize.GetSelectedControlItem(0, out openindex);

Note again: 0 is the Open Button ID And then you can do something imply with filename and this openindex. Wish to help you~