相反,您需要使用DwmEnableBlurBehindWindow API,它可以在窗口上启用玻璃模糊效果,而不需要它具有框架/边框.它需要两个参数.第一个(hWnd)是您希望应用模糊效果的表单的句柄.第二个(pBlurBehind)是通过引用传递的结构,其包含效果的数据或参数.

因此,您还必须定义DWM_BLURBEHIND structure,它本身包含四个成员.第一个(dwFlags)是constant values的按位组合,表示该结构的哪些成员已被设置.第二个(fEnable)表示您是要启用还是禁用模糊效果.第三个(hRgnBlur)允许您指定客户区域中将应用模糊效果的特定区域;将此设置为Nothing表示整个客户区域将具有模糊效果.第四个(fTransitionOnMaximized)允许您指定表单的着色是否应该过渡以匹配最大化的窗口.

以下是您必须在代码中包含以使用此函数的最终API声明：

<StructLayout(LayoutKind.Sequential)> _
Private Structure DWM_BLURBEHIND
    Public dwFlags As Integer
    Public fEnable As Boolean
    Public hRgnBlur As IntPtr
    Public fTransitionOnMaximized As Boolean
End Structure

Private Const DWM_BB_ENABLE As Integer = &H1
Private Const DWM_BB_BLURREGION As Integer = &H2
Private Const DWM_BB_TRANSITIONONMAXIMIZED As Integer = &H4

<DllImport("dwmapi.dll",PreserveSig:=False)> _
Private Shared Sub DwmEnableBlurBehindWindow(ByVal hWnd As IntPtr,ByRef pBlurBehind As DWM_BLURBEHIND)
End Sub

然后,这是一个如何在特定表单上调用此函数的简单示例：

Protected Overrides Sub OnLoad(ByVal e As System.EventArgs)
    MyBase.OnLoad(e)

    ''#Set the form's border style to None
    Me.FormBorderStyle = FormBorderStyle.None

    ''#Whatever region that you fill with black will become the glassy region
    ''# (in this example,the entire form becomes transparent)
    Me.BackColor = Color.Black

    ''#Create and populate the blur-behind structure
    Dim bb As DWM_BLURBEHIND
    bb.dwFlags = DWM_BB_ENABLE
    bb.fEnable = True
    bb.hRgnBlur = Nothing

    ''#Enable the blur-behind effect
    DwmEnableBlurBehindWindow(Me.Handle,bb)
End Sub

相反,如果您只想将模糊效果应用于表单的特定子区域,则需要为hRgnBlur成员提供有效区域,并将DWM_BB_BLURREGION标志添加到dwFlags成员.

您可以使用Region.GetHrgn method获取要指定为hRgnBlur成员的区域的句柄.例如,您可以使用以下代码而不是上述代码：

Protected Overrides Sub OnLoad(ByVal e As System.EventArgs)
    MyBase.OnLoad(e)

    ''#Set the form's border style to None
    Me.FormBorderStyle = FormBorderStyle.None

    ''#Fill the entire form with black to make it appear transparent
    Me.BackColor = Color.Black

    ''#Create a region corresponding to the area of the form you want to render as glass
    Using g As Graphics = Me.CreateGraphics
        Dim glassRect As New Rectangle(0,100,150)
        Using rgn As New Region(glassRect)
            ''#Create and populate the blur-behind structure
            Dim bb As DWM_BLURBEHIND
            bb.dwFlags = DWM_BB_ENABLE Or DWM_BB_BLURREGION
            bb.fEnable = True
            bb.hRgnBlur = rgn.GetHrgn(g)

            ''#Enable blur-behind effect
            DwmEnableBlurBehindWindow(Me.Handle,bb)
        End Using
    End Using
End Sub

注意,即使指定一个特定的子区域来应用模糊效果,我仍然将整个表单的背景颜色设置为黑色？这将导致我们指定的区域呈现玻璃般的模糊效果,并且表单的其余部分显示为透明.当然,您可以将表单背景颜色的其余部分设置为您想要的任何颜色(尽管确保填充您想要显示为黑色的玻璃矩形,如前所述),但它将显示为部分透明,没有玻璃般的模糊效果. MSDN解释了为什么会这样：

When you apply the blur-behind effect
to a subregion of the window,the
alpha channel of the window is used
for the nonblurred area. This can
cause an unexpected transparency in
the nonblurred region of a window.
Therefore,be careful when you apply a
blur effect to a subregion.

就我而言,这使得将这种效果仅应用于窗体窗口的一个子区域相对毫无价值.在我看来它唯一可能有意义的是,如果你想将任意非矩形形状渲染为玻璃状,其余形状保持透明.