To print the active Windows form in Visual Basic .NET, you must do the following:
Create a PrintDocument object to send output to the printer.
Create a class that contains the Windows GDI structures and the DllImport statements that are required to call the Windows GDI functions.
Associate the PrintDocument.PrintPage event with an event handler that is named OnPrintPage. To do this, use the AddHandler statement.
In the OnPrintPage event handler, print the current Windows device context as a graphics image to the PrintDocument object when the PrintDocument.Print method is called.
To do this, follow these steps:
In Microsoft Visual Studio .NET 2003, create a new Visual Basic Windows Application.
Add two or tree Windows Forms controls to Form1.vb. For example, add a TextBox control, a CheckBox control, and a Button control to the form.
Click the Button1 control, and change the Text property to Print in the Properties window.
In Solution Explorer, right-click Form1.vb, and then click View Code.
Add the following Imports statements to the top of the Form1.vb source code:
Note This step adds the required references to call the printing, graphic, imaging and InteropServices functions and methods.
Add the following Win32APICall class to Form1.vb after the Form1 class:
Public Class Win32APICall
Public Const DIB_RGB_COLORS = 0
Public Const BI_RGB = 0
Public Const WHITENESS = 16711778
<DllImport("user32.dll", EntryPoint:="PrintWindow", _
SetLastError:=True, CharSet:=CharSet.Unicode, _
ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function PrintWindow(ByVal hWnd As IntPtr, ByVal hDC As IntPtr, ByVal dwFlags As Integer) As UInt32
End Function
<StructLayout(LayoutKind.Sequential, pack:=8, CharSet:=CharSet.Auto)> _
Structure BITMAPINFOHEADER
Dim biSize As Int32
Dim biWidth As Int32
Dim biHeight As Int32
Dim biPlanes As Int16
Dim biBitCount As Int16
Dim biCompression As Int32
Dim biSizeImage As Int32
Dim biXPelsPerMeter As Int32
Dim biYPelsPerMeter As Int32
Dim biClrUsed As Int32
Dim biClrImportant As Int32
End Structure
<DllImport("gdi32.dll", EntryPoint:="CreateDIBSection", _
SetLastError:=True, CharSet:=CharSet.Unicode, _
ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function CreateDIBSection(ByVal hdc As IntPtr, ByRef pbmi As BITMAPINFOHEADER, _
ByVal iUsage As Int32, ByVal ppvBits As IntPtr, ByVal hSection As IntPtr, _
ByVal dwOffset As Int32) As IntPtr
End Function
<DllImport("gdi32.dll", EntryPoint:="PatBlt", _
SetLastError:=True, CharSet:=CharSet.Unicode, _
ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function PatBlt(ByVal hDC As IntPtr, ByVal nXLeft As Int32, _
ByVal nYLeft As Int32, ByVal nWidth As Int32, ByVal nHeight As Int32, _
ByVal dwRop As Int32) As Boolean
End Function
<DllImport("gdi32.dll", EntryPoint:="SelectObject", _
SetLastError:=True, CharSet:=CharSet.Unicode, _
ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function SelectObject(ByVal hDC As IntPtr, ByVal hObj As IntPtr) As IntPtr
End Function
<DllImport("GDI32.dll", EntryPoint:="CreateCompatibleDC", SetLastError:=True, CharSet:=CharSet.Unicode, _
ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function CreateCompatibleDC(ByVal hRefDC As IntPtr) As IntPtr
End Function
<DllImport("GDI32.dll", EntryPoint:="DeleteDC", SetLastError:=True, CharSet:=CharSet.Unicode, _
ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function DeleteDC(ByVal hDC As IntPtr) As Boolean
End Function
<DllImport("GDI32.dll", EntryPoint:="DeleteObject", SetLastError:=True, CharSet:=CharSet.Unicode, _
ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function DeleteObject(ByVal hObj As IntPtr) As Boolean
End Function
<DllImport("User32.dll", EntryPoint:="ReleaseDC", SetLastError:=True, CharSet:=CharSet.Unicode, _
ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function ReleaseDC(ByVal hWnd As IntPtr, ByVal hDC As IntPtr) As Boolean
End Function
<DllImport("User32.dll", EntryPoint:="GetDC", SetLastError:=True, CharSet:=CharSet.Unicode, _
ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function GetDC(ByVal hWnd As IntPtr) As IntPtr
End Function
End Class
Note This step adds the variables, the structures, and the DllImport statements that are required to call unmanaged Windows GDI API functions.
Add the following OnPrintPage event handler procedure to the Form1.vb source code in the Form1 class:
Private Sub OnPrintPage(ByVal sender As System.Object, ByVal e As System.Drawing.Printing.PrintPageEventArgs)
Dim hwndForm As IntPtr
hwndForm = Me.Handle
Dim hdcDIBSection As IntPtr
Dim hdcRef As IntPtr
Dim hbmDIBSection As IntPtr
Dim hbmDIBSectionOld As IntPtr
Dim BMPheader As Win32APICall.BITMAPINFOHEADER
hdcRef = Win32APICall.GetDC(IntPtr.Zero)
hdcDIBSection = Win32APICall.CreateCompatibleDC(hdcRef)
Win32APICall.ReleaseDC(IntPtr.Zero, hdcRef)
BMPheader.biBitCount = 24
BMPheader.biClrImportant = 0
BMPheader.biClrUsed = 0
BMPheader.biCompression = Win32APICall.BI_RGB
BMPheader.biSize = 40
BMPheader.biHeight = Me.Height
BMPheader.biPlanes = 1
BMPheader.biSizeImage = 0
BMPheader.biWidth = Me.Width
BMPheader.biXPelsPerMeter = 0
BMPheader.biYPelsPerMeter = 0
hbmDIBSection = Win32APICall.CreateDIBSection(hdcDIBSection, BMPheader, Win32APICall.DIB_RGB_COLORS, _
IntPtr.Zero, IntPtr.Zero, 0)
hbmDIBSectionOld = Win32APICall.SelectObject(hdcDIBSection, hbmDIBSection)
Win32APICall.PatBlt(hdcDIBSection, 0, 0, Me.Width, Me.Height, Win32APICall.WHITENESS)
Win32APICall.PrintWindow(hwndForm, hdcDIBSection, 0)
Win32APICall.SelectObject(hdcDIBSection, hbmDIBSectionOld)
Dim imageFrm As Bitmap
imageFrm = Image.FromHbitmap(hbmDIBSection)
e.Graphics.DrawImage(imageFrm, 0, 0)
Win32APICall.DeleteDC(hdcDIBSection)
Win32APICall.DeleteObject(hbmDIBSection)
End Sub
End Class
Note This event handler will run when the PrintDocument.Print method is executed.
Add the following code to the Click event for the Print button that you created in step 2 in the Form1 class:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim prd As PrintDocument
prd = New PrintDocument
AddHandler prd.PrintPage, AddressOf OnPrintPage
prd.Print()
End Sub
Note This step adds the code that runs when you click the Print button. The code first declares a PrintDocument object. Then, the code adds an event handler by using the AddHandler statement. This event handler runs when the PrintDocument.Print method is called.
Press CTRL-F5 to run the solution, and then click Print to print the current Windows form.
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