C# Signature:

    [DllImport("setupapi.dll", CharSet = CharSet.Auto)]
    static extern int CM_Request_Device_Eject(UInt32 devinst, out PNP_VETO_TYPE pVetoType, System.Text.StringBuilder pszVetoName, int ulNameLength, int ulFlags);
    static extern int CM_Request_Device_Eject(IntPtr devinst, out PNP_VETO_TYPE pVetoType, System.Text.StringBuilder pszVetoName, int ulNameLength, int ulFlags);

VB Signature:

Declare Function CM_Request_Device_Eject Lib "setupapi.dll" (TODO) As TODO

User-Defined Types:

    enum PNP_VETO_TYPE : int
    {
        PNP_VetoTypeUnknown = 0,
        PNP_VetoLegacyDevice = 1,
        PNP_VetoPendingClose = 2,
        PNP_VetoWindowsApp = 3,
        PNP_VetoWindowsService = 4,
        PNP_VetoOutstandingOpen = 5,
        PNP_VetoDevice = 6,
        PNP_VetoDriver = 7,
        PNP_VetoIllegalDeviceRequest = 8,
        PNP_VetoInsufficientPower = 9,
        PNP_VetoNonDisableable = 10,
        PNP_VetoLegacyDriver = 11,
        PNP_VetoInsufficientRights = 12
    }

Alternative Managed API:

Do you know one? Please contribute it!

Notes:

    CM_Query_And_Remove_SubTree has the same signature.
    CM_Request_Device_Eject_NoUi also can be used to eject a device. It has the same signature too.

    This is not the correct signature for 64-bit Windows...

Tips & Tricks:

Please add some!

Sample Code:

    // Assuming have IntPtr devinst already
    //
    // static readonly int CR_SUCCESS = 0x00000000; // cfgmgr32.h
    // static readonly int DN_REMOVABLE = 0x00004000; // cfg.h

    if (CR_SUCCESS == CM_Get_DevNode_Status(ref status, ref problem, devinst, 0) && (DN_REMOVABLE & status) > 0)
    {
        PNP_VETO_TYPE pnp_veto_type;
        System.Text.StringBuilder sb = new System.Text.StringBuilder(255);

        bool success = (CR_SUCCESS == CM_Request_Device_Eject(devinst, out pnp_veto_type, sb, sb.Capacity, 0));
    }

Sample Code:

       public string Eject(bool allowUI)
       {
       if (!allowUI)
       {

           CM_Request_Device_Eject_NoUi((int)USBData.DevInst, IntPtr.Zero, null, 0, 0); // USBData, a SP_DEVINFO_DATA structure.
       }
       else
       {
           StringBuilder sb = new StringBuilder(1024);

           PNP_VETO_TYPE veto; // PNP_VETO_TYPE enumeration is used to identify the reason for rejection
           int hr = CM_Request_Device_Eject((int)USBData.DevInst, out veto, sb, sb.Capacity, 0);

           if (hr != 0)
           throw new Win32Exception(hr);
           if (veto != PNP_VETO_TYPE.Ok)
           return veto.ToString();
       }
       return null;
       }

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