C# Signature:

[DllImport("user32.dll")]
static extern void mouse_event(uint dwFlags, int dx, int dy, uint dwData,
UIntPtr dwExtraInfo);

[DllImport("user32.dll")]
static extern void mouse_event(uint dwFlags, int dx, int dy, uint dwData,
int dwExtraInfo);

VB.NET Signature:

<DllImport("user32.dll")> _
Private Shared Sub mouse_event(dwFlags As UInteger, dx As UInteger, dy As UInteger, dwData As UInteger, dwExtraInfo As Integer)
End Sub

VB Signature

Public Declare Sub mouse_event Lib "user32" (ByVal dwFlags As Long, ByVal dx As Long, ByVal dy As Long, ByVal dwData As Long, ByVal dwExtraInfo As Long)

Note that for non-relative mouse movement (i.e. if MOUSEEVENTF_ABSOLUTE is not specified as part of dwFlags), negative values for dx and dy are desirable. As such, the "uint" type specification for C# can be safely replaced with Int32.

User-Defined Constants:

C#:

const uint MOUSEEVENTF_ABSOLUTE = 0x8000;
const uint MOUSEEVENTF_LEFTDOWN = 0x0002;
const uint MOUSEEVENTF_LEFTUP = 0x0004;
const uint MOUSEEVENTF_MIDDLEDOWN = 0x0020;
const uint MOUSEEVENTF_MIDDLEUP = 0x0040;
const uint MOUSEEVENTF_MOVE = 0x0001;
const uint MOUSEEVENTF_RIGHTDOWN = 0x0008;
const uint MOUSEEVENTF_RIGHTUP = 0x0010;
const uint MOUSEEVENTF_XDOWN = 0x0080;
const uint MOUSEEVENTF_XUP = 0x0100;
const uint MOUSEEVENTF_WHEEL = 0x0800;
const uint MOUSEEVENTF_HWHEEL = 0x01000;

VB.NET:

<Flags()> _
Public Enum MouseEventFlags As UInteger
     MOUSEEVENTF_ABSOLUTE = &H8000
     MOUSEEVENTF_LEFTDOWN = &H2
     MOUSEEVENTF_LEFTUP = &H4
     MOUSEEVENTF_MIDDLEDOWN = &H20
     MOUSEEVENTF_MIDDLEUP = &H40
     MOUSEEVENTF_MOVE = &H1
     MOUSEEVENTF_RIGHTDOWN = &H8
     MOUSEEVENTF_RIGHTUP = &H10
     MOUSEEVENTF_XDOWN = &H80
     MOUSEEVENTF_XUP = &H100
     MOUSEEVENTF_WHEEL = &H800
     MOUSEEVENTF_HWHEEL = &H1000
End Enum

User-Defined Types:

  [Flags]
  public enum MouseEventFlags : uint
  {
    LEFTDOWN   = 0x00000002,
    LEFTUP     = 0x00000004,
    MIDDLEDOWN = 0x00000020,
    MIDDLEUP   = 0x00000040,
    MOVE       = 0x00000001,
    ABSOLUTE   = 0x00008000,
    RIGHTDOWN  = 0x00000008,
    RIGHTUP    = 0x00000010,
    WHEEL      = 0x00000800,
    XDOWN      = 0x00000080,
    XUP    = 0x00000100
  }

  //Use the values of this enum for the 'dwData' parameter
  //to specify an X button when using MouseEventFlags.XDOWN or
  //MouseEventFlags.XUP for the dwFlags parameter.
  public enum MouseEventDataXButtons : uint
  {
    XBUTTON1   = 0x00000001,
    XBUTTON2   = 0x00000002
  }

VB.Net Signature:

This function does indeed return a value, just as the keybd_event API does.

If there is a real error, it will in fact return a value of false, or zero.

The dwExtraInfo appears to be a ULONG_PTR in C++ (IntPtr in VB.NET)

Declare Function apimouse_event Lib "user32.dll" Alias "mouse_event" (ByVal dwFlags As Int32, ByVal dX As Int32, ByVal dY As Int32, ByVal cButtons As Int32, ByVal dwExtraInfo As Int32) As Boolean

Notes:

FYI, Microsoft tells us for "Windows NT/2000/XP: This function has been superseded. Use SendInput instead."

The C# code below works fine. However you have to keep in mind to add the namespace "System.Runtime.InteropServices" and keep in mind to write the code into a class.

Original contributor tells us:aa

I wanted to emulate the scroll. Searching for this information wasn't easy ... but here is how you do the mouse scroll button

dim ScrollValue as Integer

ScrollValue = 120 'or -120 for up or down scrolling

mouse_event(&H800, 0, 0, ScrollValue, 0)

Tips & Tricks:

Another contributor tells us:

The scroll value can actually be any value larger than 1, if used within a loop.

This allows you to smoothly increment the scrollbar, instead of relying on the inconsistent wheel delta,

which is a variable limited by the user, for mouse wheel. Start-Control Panel-Mouse-Wheel-Scrolling

C# Sample Code 1:

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

using System.Runtime.InteropServices;
using System.Threading;

namespace PInvoke_DllImport_Cs
{
     public partial class Form1 : Form
     {
     public Form1()
     {
         InitializeComponent();
     }

     const uint MOUSEEVENTF_LEFTDOWN = 0x0002;
     const uint MOUSEEVENTF_LEFTUP = 0x0004;

     [DllImport("user32.dll")]
     private static extern void mouse_event(uint dwFlags, uint dx, uint dy, uint dwData, int dwExtraInfo);

     private void timer1_Tick(System.Object sender, System.EventArgs e)
     {
         mouse_event(MOUSEEVENTF_LEFTDOWN, 0, 0, 0, 0);
         Thread.Sleep(100);
         mouse_event(MOUSEEVENTF_LEFTUP, 0, 0, 0, 0);
     }
     }
}

C# Sample Code 2:

    [DllImport("user32.dll")]
    static extern void mouse_event(int dwFlags, int dx, int dy, int dwData, int dwExtraInfo);

    [Flags]
    public enum MouseEventFlags
    {
        LEFTDOWN = 0x00000002,
        LEFTUP = 0x00000004,
        MIDDLEDOWN = 0x00000020,
        MIDDLEUP = 0x00000040,
        MOVE = 0x00000001,
        ABSOLUTE = 0x00008000,
        RIGHTDOWN = 0x00000008,
        RIGHTUP = 0x00000010
    }

    public static void LeftClick(int x, int y)
    {
        Cursor.Position = new System.Drawing.Point(x, y);
        mouse_event((int)(MouseEventFlags.LEFTDOWN), 0, 0, 0, 0);
        mouse_event((int)(MouseEventFlags.LEFTUP), 0, 0, 0, 0);
    }

VB.NET Sample Code 1:

' Clicks left mouse button in current coordinates

Imports System.Runtime.InteropServices
Imports System.Threading

Public Class Form1

     Const MOUSEEVENTF_LEFTDOWN As UInteger = &H2 '0x0002
     Const MOUSEEVENTF_LEFTUP As UInteger = &H4 '0x0004

     <DllImport("user32.dll")> _
     Private Shared Sub mouse_event(ByVal dwFlags As UInteger, ByVal dx As UInteger, ByVal dy As UInteger, ByVal dwData As UInteger, ByVal dwExtraInfo As Integer)
     End Sub

     'Public Declare Sub mouse_event Lib "user32" (ByVal dwFlags As Long, ByVal dx As Long, ByVal dy As Long, ByVal dwData As Long, ByVal dwExtraInfo As Long)

     Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
     mouse_event(MOUSEEVENTF_LEFTDOWN, 0, 0, 0, 0)
     Thread.Sleep(100)
     mouse_event(MOUSEEVENTF_LEFTUP, 0, 0, 0, 0)
     End Sub

End Class

VB.NET Sample Code 2:

    Const MOUSEEVENTF_WHEEL As Int32 = 2048
    Const MOUSEEVENTF_WHEEL_DELTA As Int32 = 120

    Private Declare Function apimouse_event Lib "user32" Alias "mouse_event" (ByVal dwFlags As Int32, ByVal dX As Int32, ByVal dY As Int32, ByVal cButtons As Int32, ByVal dwExtraInfo As Int32) As Boolean
    Private Declare Function apiGetMessageExtraInfo Lib "user32" Alias "GetMessageExtraInfo" () As Int32

    Private Sub PlayScroll(ByVal number As Int32, Optional ByVal increment As Int32 = 2)
    On Error Resume Next
    For i As Int32 = 1 To number
        apimouse_event(MOUSEEVENTF_WHEEL, 0, 0, increment, apiGetMessageExtraInfo)
    Next
    End Sub

VB.NET 2005 Sample Code:

Based on http://vb-helper.com/howto_move_click_mouse.html

This code assumes a form called frmMain with a command button called cmdClick a picture box called picClicker and a text box called txtResults

Note Twips are no more. Also, I stripped the FOR loop of delta moves from the command button click to the middle of the picture box.

Option Explicit On

Friend Class frmMain

    Inherits System.Windows.Forms.Form

    Declare Auto Sub mouse_event Lib "user32" (ByVal dwFlags As Int32, ByVal dx As Int32, ByVal dy As Int32, ByVal cButtons As Int32, ByVal dwExtraInfo As IntPtr)

    Const MOUSEEVENTF_MOVE As Int32 = &H1 '  mouse move
    Const MOUSEEVENTF_LEFTDOWN As Int32 = &H2 '  left button down
    Const MOUSEEVENTF_LEFTUP As Int32 = &H4 '  left button up
    Const MOUSEEVENTF_RIGHTDOWN As Int32 = &H8 '  right button down
    Const MOUSEEVENTF_RIGHTUP As Int32 = &H10 '  right button up
    Const MOUSEEVENTF_MIDDLEDOWN As Int32 = &H20 '  middle button down
    Const MOUSEEVENTF_MIDDLEUP As Int32 = &H40 '  middle button up
    Const MOUSEEVENTF_ABSOLUTE As Int32 = &H8000 '  absolute move
    Const MOUSEEVENTF_WHEEL As Int32 = &H800 ' wheel button rolled

    ' Simulate moving the mouse to the center of the
    ' PictureBox and clicking.
    Private Sub cmdClick_Click(ByVal eventSender As System.Object, ByVal eventArgs As System.EventArgs) Handles cmdClick.Click
    Dim cur_x As Single
    Dim cur_y As Single
    Dim dest_x As Single
    Dim dest_y As Single

    ' mouse_event moves in a coordinate system where
    ' (0, 0) is in the upper left corner and
    ' (65535,65535) is in the lower right corner.

    ' Get the current mouse coordinates and convert
    ' them into this new system.
    cur_x = System.Windows.Forms.Cursor.Position.X * 65535 / System.Windows.Forms.Screen.PrimaryScreen.Bounds.Width
    cur_y = System.Windows.Forms.Cursor.Position.Y * 65535 / System.Windows.Forms.Screen.PrimaryScreen.Bounds.Height

    ' Convert the coordinates of the center of the
    ' picClicker PictureBox into this new system.
    Dim pt As Point = picClicker.PointToScreen(New Point(picClicker.ClientRectangle.Width / 2, picClicker.ClientRectangle.Height / 2))

    dest_x = pt.X * 65535 / System.Windows.Forms.Screen.PrimaryScreen.Bounds.Width
    dest_y = pt.Y * 65535 / System.Windows.Forms.Screen.PrimaryScreen.Bounds.Height

    txtResults.Text = txtResults.Text & "From " & System.Windows.Forms.Cursor.Position.X & " " & System.Windows.Forms.Cursor.Position.Y & " to " & pt.X & " " & pt.Y & vbCrLf
    txtResults.Text = txtResults.Text & "From " & cur_x & " " & cur_y & " to " & dest_x & " " & dest_y & vbCrLf

    ' Move the mouse to its final destination and click it.
    mouse_event(MOUSEEVENTF_ABSOLUTE + MOUSEEVENTF_MOVE + MOUSEEVENTF_LEFTDOWN + MOUSEEVENTF_LEFTUP, dest_x, dest_y, 0, 0)
    End Sub

    Private Sub picClicker_Click(ByVal eventSender As System.Object, ByVal eventArgs As System.EventArgs) Handles picClicker.Click
    txtResults.Text = txtResults.Text & "MouseClick" & vbCrLf
    End Sub

    Private Sub picClicker_MouseDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles picClicker.MouseDown
    txtResults.Text = txtResults.Text & "MouseDown (" & e.X & ", " & e.Y & ")" & vbCrLf
    End Sub

    Private Sub picClicker_MouseUp(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles picClicker.MouseUp
    txtResults.Text = txtResults.Text & "MouseUp (" & e.X & ", " & e.Y & ")" & vbCrLf
    End Sub

End Class

Alternative Managed API:

Per http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dndotnet/html/win32map.asp , mouse_event is supposed to be replaced by .NET Framework API System.Windows.Forms.MouseEventArgs but this is not the case. MouseEventArgs is just a data structure w/out event capability. I tried to get:

Dim eMouse As New System.Windows.Forms.MouseEventArgs(Windows.Forms.MouseButtons.Left, 1, pt.X, pt.Y, 0)

Me.OnMouseDown(eMouse)

Me.OnMouseMove(eMouse)

Me.OnMouseUp(eMouse)

to work as desired. Although it did trigger mouse events in the form showing the movement and click action desired, it didn't move the mouse pointer on the screen nor did it trigger events in the picture box located at pt.X, pt.Y

Thus I have resigned myself to unmanaged code for now. I will post the SendInput version shortly as mouse_event has been deprecated by Bill in favor of SendInput.

As the original contributor noted:

You can use the System.Windows.Forms.Cursor.Position property to set the position of the mouse, if you would like.

You will note I have replaced the GetCursorPos calls in the original VB source with this as suggested in the MSDN URL I mention above.

Documentation

mouse_event on MSDN

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