利用API函数

 Private Declare Function CreateCompatibleDC Lib "GDI32" (ByVal hDC As Integer) As Integer
    Private Declare Function CreateCompatibleBitmap Lib "GDI32" (ByVal hDC As Integer,ByVal nWidth As Integer,ByVal nHeight As Integer) As Integer
    Private Declare Function SelectObject Lib "GDI32" (ByVal hDC As Integer,ByVal hObject As Integer) As Integer
    Private Declare Function BitBlt Lib "GDI32" (ByVal srchDC As Integer,ByVal srcX As Integer,ByVal srcY As Integer,ByVal srcW As Integer,ByVal srcH As Integer,ByVal desthDC As Integer,ByVal destX As Integer,ByVal destY As Integer,ByVal op As Integer) As Integer
    Private Declare Function DeleteDC Lib "GDI32" (ByVal hDC As Integer) As Integer
    Private Declare Function DeleteObject Lib "GDI32" (ByVal hObj As Integer) As Integer
    Declare Function GetDC Lib "user32" Alias "GetDC" (ByVal hwnd As Integer) As Integer
    Const SRCCOPY As Integer = &HCC0020

非API函数：

  Dim img As New Bitmap(Screen.PrimaryScreen.Bounds.Width,Screen.PrimaryScreen.Bounds.Height)
         
        Using g As Graphics = Graphics.FromImage(img)
            g.CopyFromScreen(New Point(0,0),New Point(0,img.Size)
            'g.Clear(Color.LightBlue);
            g.Save()
        End Using

使用以上代码可能需要导入：

Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Data
Imports System.Text
Imports System.Windows.Forms
Imports System.Drawing