[C#]ImageSearch DLL crasht

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

namespace ImageSearch
{
    public class Program
    {
        public static Int32 iPosX = 0;
        public static Int32 iPosY = 0;
        [DllImport("ImageSearchDLL.dll")]
        public static extern String ImageSearch(Int32 PosX, Int32 PosY, Int32 PosRight, Int32 PosBottom, String Image);
        public static void Main(string[] args)
        {
            if (ImageSearch("bild.png", false, iPosX, iPosY, 0))
            {
                MessageBox.Show(iPosX + "|" + iPosY);
            }
            else
            {
                MessageBox.Show("Not found");
            }
        }

        public static Boolean ImageSearch(String sImage, Boolean resultPosition, Int32 iPosX, Int32 iPosY, Int32 iTolerance)
        {
            return ImageSearchArea(sImage, resultPosition, 0, 0, SystemInformation.VirtualScreen.Width, SystemInformation.VirtualScreen.Height, iPosX, iPosY, iTolerance);
        }
        //$findImage,$resultPosition,$x1,$y1,$right,$bottom,ByRef $x, ByRef $y, $tolerance
        public static Boolean ImageSearchArea(String sImage, Boolean resultPosition, Int32 iStartX, Int32 iStartY, Int32 iRight, Int32 iBottom, Int32 iPosX, Int32 iPosY, Int32 iTolerance)
        {
            if (iTolerance > 0) { sImage = "*" + iTolerance + " " + sImage; }
            String result = ImageSearch(iPosX, iPosY, iRight, iBottom, sImage);
            if (result == "0") { return false; }
            String[] aResult = result.Split('|');
            iPosX = Convert.ToInt32(aResult[2]);
            iPosY = Convert.ToInt32(aResult[3]);
            if (resultPosition)
            {
                iPosX = iPosX + Convert.ToInt32(aResult[4]) / 2;
                iPosY = iPosY + Convert.ToInt32(aResult[5]) / 2;
            }
            return true;
        }
    }
}