C# Definition:

//[StructLayout(LayoutKind.Sequential, CharSet=CharSet.Unicode)]
//If you use the above you may encounter an invalid memory access exception (when using ANSI
//or see nothing (when using unicode) when you use FOF_SIMPLEPROGRESS flag.
[StructLayout(LayoutKind.Sequential, CharSet=CharSet.Unicode)]
struct SHFILEOPSTRUCT
{
    public IntPtr hwnd;
    public FILEOP_FLAGS wFunc;
    [MarshalAs(UnmanagedType.LPWStr)]
    public string pFrom;
    [MarshalAs(UnmanagedType.LPWStr)]
    public string pTo;
    public ushort fFlags;
    //typedef int BOOL; (in platform SDK)
    //BOOL fAnyOperationsAborted; (in platform SDK)
    //public bool fAnyOperationsAborted;
    public Int32 fAnyOperationsAborted;
    public IntPtr hNameMappings;
    [MarshalAs(UnmanagedType.LPWStr)]
    public string lpszProgressTitle;
}

VB Definition:

<StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Unicode)> _
Public Structure SHFILEOPSTRUCT
    Public hwnd As IntPtr
    Public wFunc As FO_Func
    <MarshalAs(UnmanagedType.LPWStr)> _
    Public pFrom As String
    <MarshalAs(UnmanagedType.LPWStr)> _
    Public pTo As String
    Public fFlags As FILEOP_FLAGS
    Public fAnyOperationsAborted As Boolean
    Public hNameMappings As IntPtr
    <MarshalAs(UnmanagedType.LPWStr)> _
    Public lpszProgressTitle As String '  only used if FOF_SIMPLEPROGRESS
End Structure

User-Defined Field Types:

FILEOP_FLAGS

Notes:

I tried to use this to send files to the recycle bin. It failed (Marshal.GetLastWin32Error was 6, invalid handle) and sometimes threw a NullReferenceException. To make it work I did the following;

• Change from LPWStr to IntPtr for pFrom and pTo

    public IntPtr pFrom;
    public IntPtr pTo;

• Always set hwnd to my main app window (I was using IntPtr.Zero, this might not be required)
• Correctly treat pTo and pFrom as zero delimited double zero terminated.

In my case I only needed pTo so I just added a null byte to the end and used Marshal.StringToHGlobalUni() to set the value

Failure on 64 bit OS

Under x64, the SHFILEOPSTRUCT must be declared without the Pack = 1 parameter, or it will fail. This is a real pain if you want your code to be platform independent, as you have to declare two separate structures, one with Pack = 1, and one without. You then have to declare two different SHFileOperation calls, one for each of the structures. Then you have to decide which one to call depending on whether you are running on 32 or 64 bit.

Update on 64-bit Issue

Don't declare a value for the Pack size. If you omit it, the correct value is used when marshaling and a single SHFILEOPSTRUCT can be used for both 32-bit and 64-bit operation.

64 bit proof alternative

You may use the functionality of the Microsoft.VisualBasic.dll(.NET framework) instead. They handle the 64 bit call well.

using Microsoft.VisualBasic.FileIO;

FileSystem.DeleteFile(path, UIOption.OnlyErrorDialogs, RecycleOption.SendToRecycleBin);