mouse_event not firing on a specific application (C#)

Question

I am trying to programatically simulate a left button mouse click:

        [DllImport("user32.dll")]
        static extern bool SetCursorPos(int x, int y);

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

        public const int MOUSEEVENTF_LEFTDOWN = 0x02;
        public const int MOUSEEVENTF_LEFTUP = 0x04;    

        public static void LeftMouseClick(int xpos, int ypos)
        {
            SetCursorPos(xpos, ypos);
            mouse_event(MOUSEEVENTF_LEFTDOWN, xpos, ypos, 0, 0);
            System.Threading.Thread.Sleep(1000);
            mouse_event(MOUSEEVENTF_LEFTUP, xpos, ypos, 0, 0);
        }

The cursor moves to the appropriate position on the screen, but the click is not firing there. Any thoughts?

EDIT: I did a couple of tests. The method i use does not seem to be the issue (it clicks on applications like steam, skype successfully). When calling the click method when the cursor is above the application that i specifically want to click on (an android emulator) nothing happens. The mouse cursor moves to the spot but wont click... Going to test another emulator now.

Answer 1

I wrote a helper class for another project I was working on which wrapped up the mouse event:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;

class MouseHelper
{
    internal struct INPUT
    {
        public UInt32 Type;
        public MOUSEKEYBDHARDWAREINPUT Data;
    }
    [StructLayout(LayoutKind.Explicit)]
    internal struct MOUSEKEYBDHARDWAREINPUT
    {
        [FieldOffset(0)]
        public MOUSEINPUT Mouse;
    }

    internal struct MOUSEINPUT
    {
        public Int32 X;
        public Int32 Y;
        public UInt32 MouseData;
        public UInt32 Flags;
        public UInt32 Time;
        public IntPtr ExtraInfo;
    }

    /// <summary>
    /// Synthesizes keystrokes, mouse motions, and button clicks.
    /// </summary>
    [DllImport("user32.dll")]
    internal static extern uint SendInput(uint nInputs, [MarshalAs(UnmanagedType.LPArray), In] INPUT[] pInputs, int cbSize);
    [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
    public static extern void mouse_event(long dwFlags, long dx, long dy, long cButtons, long dwExtraInfo);

    private const int MOUSEEVENTF_LEFTDOWN = 0x02;
    private const int MOUSEEVENTF_LEFTUP = 0x04;
    private const int MOUSEEVENTF_RIGHTDOWN = 0x08;
    private const int MOUSEEVENTF_RIGHTUP = 0x10;

    public static void DoMouseClick()
    {
        var inputMouseDown = new INPUT();
        inputMouseDown.Type = 0; /// input type mouse
        inputMouseDown.Data.Mouse.Flags = 0x0002; /// left button down

        var inputMouseUp = new INPUT();
        inputMouseUp.Type = 0; /// input type mouse
        inputMouseUp.Data.Mouse.Flags = 0x0004; /// left button up

        var inputs = new INPUT[] { inputMouseDown, inputMouseUp };
        SendInput((uint)inputs.Length, inputs, Marshal.SizeOf(typeof(INPUT)));
    }

    public static void DoMouseClick2()
    {
        mouse_event(MOUSEEVENTF_LEFTDOWN | MOUSEEVENTF_LEFTUP, 0, 0, 0, 0);
    }
}

All I needed to do was call MouseHelper.DoMouseClick() whenever I wanted a mouse click. I suspect the mouse move functionality could be added as an enhancement.