No success to simulate mouse click in C#

I'm new to C# and I want to simulate a mouse click(I'm using visual studio 2017 on windows 10). I found this code:

using System;
using System.Runtime.InteropServices;

public class MouseOperations
{
    [Flags]
    public enum MouseEventFlags
    {
        LeftDown = 0x00000002,
        LeftUp = 0x00000004,
        MiddleDown = 0x00000020,
        MiddleUp = 0x00000040,
        Move = 0x00000001,
        Absolute = 0x00008000,
        RightDown = 0x00000008,
        RightUp = 0x00000010
    }

    [DllImport("user32.dll", EntryPoint = "SetCursorPos")]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static extern bool SetCursorPos(int x, int y);      

    [DllImport("user32.dll")]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static extern bool GetCursorPos(out MousePoint lpMousePoint);

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

    public static void SetCursorPosition(int x, int y) 
    {
        SetCursorPos(x, y);
    }

    public static void SetCursorPosition(MousePoint point)
    {
        SetCursorPos(point.X, point.Y);
    }

    public static MousePoint GetCursorPosition()
    {
        MousePoint currentMousePoint;
        var gotPoint = GetCursorPos(out currentMousePoint);
        if (!gotPoint) { currentMousePoint = new MousePoint(0, 0); }
        return currentMousePoint;
    }

    public static void MouseEvent(MouseEventFlags value)
    {
        MousePoint position = GetCursorPosition();

        mouse_event
            ((int)value,
             position.X,
             position.Y,
             0,
             0)
            ;
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct MousePoint
    {
        public int X;
        public int Y;

        public MousePoint(int x, int y)
        {
            X = x;
            Y = y;
        }
    }
}

but it doesn't work for me. I think maybe it's because I don't use it in the right way.

This is how I try to simulate a mouse left button down: MouseOperations.MouseEvent(MouseOperations.MouseEventFlags.LeftDown);

My full code: https://pastebin.com/TZ64u0TM

Try updating the mouse_event declaration with this on instead:

[DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
public static extern void mouse_event(uint dwFlags, uint dx, uint dy, uint cButtons, uint dwExtraInfo);

I am currently using this code on Windows 10 and have had no issues with it. I can share my entire MouseEvent file if needed.