C# Definition:

[Flags()]
private enum RedrawWindowFlags : uint
{
    /// <summary>
    /// Invalidates the rectangle or region that you specify in lprcUpdate or hrgnUpdate.
    /// You can set only one of these parameters to a non-NULL value. If both are NULL, RDW_INVALIDATE invalidates the entire window.
    /// </summary>
    Invalidate = 0x1,

    /// <summary>Causes the OS to post a WM_PAINT message to the window regardless of whether a portion of the window is invalid.</summary>
    InternalPaint = 0x2,

    /// <summary>
    /// Causes the window to receive a WM_ERASEBKGND message when the window is repainted.
    /// Specify this value in combination with the RDW_INVALIDATE value; otherwise, RDW_ERASE has no effect.
    /// </summary>
    Erase = 0x4,

    /// <summary>
    /// Validates the rectangle or region that you specify in lprcUpdate or hrgnUpdate.
    /// You can set only one of these parameters to a non-NULL value. If both are NULL, RDW_VALIDATE validates the entire window.
    /// This value does not affect internal WM_PAINT messages.
    /// </summary>
    Validate = 0x8,

    /// <summary>
    /// Suppresses any pending internal WM_PAINT messages.
    /// This flag does not affect WM_PAINT messages resulting from a non-NULL update area.
    /// </summary>
    NoInternalPaint = 0x10,

    /// <summary>Suppresses any pending WM_ERASEBKGND messages.</summary>
    NoErase = 0x20,

    /// <summary>Excludes child windows, if any, from the repainting operation.</summary>
    NoChildren = 0x40,

    /// <summary>Includes child windows, if any, in the repainting operation.</summary>
    AllChildren = 0x80,

    /// <summary>Causes the affected windows, which you specify by setting the RDW_ALLCHILDREN and RDW_NOCHILDREN values, to receive WM_ERASEBKGND and WM_PAINT messages before the RedrawWindow returns, if necessary.</summary>
    UpdateNow = 0x100,

    /// <summary>
    /// Causes the affected windows, which you specify by setting the RDW_ALLCHILDREN and RDW_NOCHILDREN values, to receive WM_ERASEBKGND messages before RedrawWindow returns, if necessary.
    /// The affected windows receive WM_PAINT messages at the ordinary time.
    /// </summary>
    EraseNow = 0x200,

    /// <summary>
    /// Causes any part of the nonclient area of the window that intersects the update region to receive a WM_NCPAINT message.
    /// The RDW_INVALIDATE flag must also be specified; otherwise, RDW_FRAME has no effect.
    /// The WM_NCPAINT message is typically not sent during the execution of RedrawWindow unless either RDW_UPDATENOW or RDW_ERASENOW is specified.
    /// </summary>
    Frame = 0x400,

    /// <summary>
    /// Suppresses any pending WM_NCPAINT messages.
    /// This flag must be used with RDW_VALIDATE and is typically used with RDW_NOCHILDREN.
    /// RDW_NOFRAME should be used with care, as it could cause parts of a window to be painted improperly.
    /// </summary>
    NoFrame = 0x800
}

VB.NET Definition:

<Flags()> _
Private Enum RedrawWindowFlags As UInteger
    ''' <summary>
    ''' Invalidates the rectangle or region that you specify in lprcUpdate or hrgnUpdate.
    ''' You can set only one of these parameters to a non-NULL value. If both are NULL, RDW_INVALIDATE invalidates the entire window.
    ''' </summary>
    Invalidate = &H1

    ''' <summary>Causes the OS to post a WM_PAINT message to the window regardless of whether a portion of the window is invalid.</summary>
    InternalPaint = &H2

    ''' <summary>
    ''' Causes the window to receive a WM_ERASEBKGND message when the window is repainted.
    ''' Specify this value in combination with the RDW_INVALIDATE value; otherwise, RDW_ERASE has no effect.
    ''' </summary>
    [Erase] = &H4

    ''' <summary>
    ''' Validates the rectangle or region that you specify in lprcUpdate or hrgnUpdate.
    ''' You can set only one of these parameters to a non-NULL value. If both are NULL, RDW_VALIDATE validates the entire window.
    ''' This value does not affect internal WM_PAINT messages.
    ''' </summary>
    Validate = &H8

    NoInternalPaint = &H10

    ''' <summary>Suppresses any pending WM_ERASEBKGND messages.</summary>
    NoErase = &H20

    ''' <summary>Excludes child windows, if any, from the repainting operation.</summary>
    NoChildren = &H40

    ''' <summary>Includes child windows, if any, in the repainting operation.</summary>
    AllChildren = &H80

    ''' <summary>Causes the affected windows, which you specify by setting the RDW_ALLCHILDREN and RDW_NOCHILDREN values, to receive WM_ERASEBKGND and WM_PAINT messages before the RedrawWindow returns, if necessary.</summary>
    UpdateNow = &H100

    ''' <summary>
    ''' Causes the affected windows, which you specify by setting the RDW_ALLCHILDREN and RDW_NOCHILDREN values, to receive WM_ERASEBKGND messages before RedrawWindow returns, if necessary.
    ''' The affected windows receive WM_PAINT messages at the ordinary time.
    ''' </summary>
    EraseNow = &H200

    Frame = &H400

    NoFrame = &H800
End Enum

Notes:

None.