Select file or folder from the same dialog

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FileFolderDialog

Introduction

This code demonstrates a way to use the managed FileOpenDialog control (available in .NET 2.0+) to open either a file or a folder from within the same dialog.

Background

For my Open-Source project, I was looking for a control that would allow users to select either a file or a folder from within the same dialog. Having searched the web, I came across a few solutions (one involving calling non-managed code, and one involving a custom-written control). Unfortunately, both solutions didn't work for me. The first one used the FolderSelect dialog (which is pretty inconvenient compared to the FileOpen dialog), and the second one did not provide 100% of the Windows dialog functionality.

I then decided to look into the source code of the WinMerge utility to see how they implemented similar functionality in C++ (and potentially used some native calls). It turned out that the solution was available right inside the .NET framework.

Using the code

The key to getting OpenFileDialog to select both files and folders is to set the ValidateNames and CheckFileExists properties to false (dialog.ValidateNames = false; dialog.CheckFileExists = false) and set FileName to some special keyword to make sure that folders get selected (dialog.FileName = "Folder Selection";).

// Set validate names and check file exists to false otherwise windows will
// not let you select "Folder Selection."
dialog.ValidateNames = false;
dialog.CheckFileExists = false;
dialog.CheckPathExists = true;

...

// Always default to Folder Selection.
dialog.FileName = "Folder Selection.";

For convenience, I have wrapped OpenFileDialog inside a custom class, FileFolderDialog, and have also added a few helper properties to parse the returned file name.