Help with ImageSearch.DLL and C#

So I'm trying to port this code from the ImageSearch.Dll into C# and I think I have some type of conversion errors but C# is not catching the unmanaged exception and instead just crashed the program. I'm curious if anyone here can lend me a hand in debugging this. Here is the original Autoit code.

AutoIt

#include-once
; ------------------------------------------------------------------------------
;
; AutoIt Version: 3.0
; Language:       English
; Description:    Functions that assist with Image Search
;                 Require that the ImageSearchDLL.dll be loadable
;
; ------------------------------------------------------------------------------

;===============================================================================
;
; Description:      Find the position of an image on the desktop
; Syntax:           _ImageSearchArea, _ImageSearch
; Parameter(s):
;                   $findImage - the image to locate on the desktop
;                   $tolerance - 0 for no tolerance (0-255). Needed when colors of
;                                image differ from desktop. e.g GIF
;                   $resultPosition - Set where the returned x,y location of the image is.
;                                     1 for centre of image, 0 for top left of image
;                   $x $y - Return the x and y location of the image
;
; Return Value(s):  On Success - Returns 1
;                   On Failure - Returns 0
;
; Note: Use _ImageSearch to search the entire desktop, _ImageSearchArea to specify
;       a desktop region to search
;
;===============================================================================
Func _ImageSearch($findImage,$resultPosition,ByRef $x, ByRef $y,$tolerance)
   return _ImageSearchArea($findImage,$resultPosition,0,0,@DesktopWidth,@DesktopHeight,$x,$y,$tolerance)
EndFunc

Func _ImageSearchArea($findImage,$resultPosition,$x1,$y1,$right,$bottom,ByRef $x, ByRef $y, $tolerance)
    ;MsgBox(0,"asd","" & $x1 & " " & $y1 & " " & $right & " " & $bottom)
    if $tolerance>0 then $findImage = "*" & $tolerance & " " & $findImage
    $result = DllCall("ImageSearchDLL.dll","str","ImageSearch","int",$x1,"int",$y1,"int",$right,"int",$bottom,"str",$findImage)

    ; If error exit
    if $result[0]="0" then return 0

    ; Otherwise get the x,y location of the match and the size of the image to
    ; compute the centre of search
    $array = StringSplit($result[0],"|")

   $x=Int(Number($array[2]))
   $y=Int(Number($array[3]))
   if $resultPosition=1 then
      $x=$x + Int(Number($array[4])/2)
      $y=$y + Int(Number($array[5])/2)
   endif
   return 1
EndFunc

;===============================================================================
;
; Description:      Wait for a specified number of seconds for an image to appear
;
; Syntax:           _WaitForImageSearch, _WaitForImagesSearch
; Parameter(s):
;                   $waitSecs  - seconds to try and find the image
;                   $findImage - the image to locate on the desktop
;                   $tolerance - 0 for no tolerance (0-255). Needed when colors of
;                                image differ from desktop. e.g GIF
;                   $resultPosition - Set where the returned x,y location of the image is.
;                                     1 for centre of image, 0 for top left of image
;                   $x $y - Return the x and y location of the image
;
; Return Value(s):  On Success - Returns 1
;                   On Failure - Returns 0
;
;
;===============================================================================
Func _WaitForImageSearch($findImage,$waitSecs,$resultPosition,ByRef $x, ByRef $y,$tolerance)
    $waitSecs = $waitSecs * 1000
    $startTime=TimerInit()
    While TimerDiff($startTime) < $waitSecs
        sleep(100)
        $result=_ImageSearch($findImage,$resultPosition,$x, $y,$tolerance)
        if $result > 0 Then
            return 1
        EndIf
    WEnd
    return 0
EndFunc

;===============================================================================
;
; Description:      Wait for a specified number of seconds for any of a set of
;                   images to appear
;
; Syntax:           _WaitForImagesSearch
; Parameter(s):
;                   $waitSecs  - seconds to try and find the image
;                   $findImage - the ARRAY of images to locate on the desktop
;                              - ARRAY[0] is set to the number of images to loop through
;                                ARRAY[1] is the first image
;                   $tolerance - 0 for no tolerance (0-255). Needed when colors of
;                                image differ from desktop. e.g GIF
;                   $resultPosition - Set where the returned x,y location of the image is.
;                                     1 for centre of image, 0 for top left of image
;                   $x $y - Return the x and y location of the image
;
; Return Value(s):  On Success - Returns the index of the successful find
;                   On Failure - Returns 0
;
;
;===============================================================================
Func _WaitForImagesSearch($findImage,$waitSecs,$resultPosition,ByRef $x, ByRef $y,$tolerance)
    $waitSecs = $waitSecs * 1000
    $startTime=TimerInit()
    While TimerDiff($startTime) < $waitSecs
        for $i = 1 to $findImage[0]
            sleep(100)
            $result=_ImageSearch($findImage[$i],$resultPosition,$x, $y,$tolerance)
            if $result > 0 Then
                return $i
            EndIf
        Next
    WEnd
    return 0
EndFunc

And here is my c# code. As soon as it tried to call ImageSearch, the program crashes without any exception.

 [DllImport("ImageSearchDLL.dll")]
        static extern string ImageSearch(int aLeft, int aTop, int aRight, int aBottom, string aImageFile);
      
        public static Point _ImageSearch(string findImage, bool resultPosition, int tolerance)
        {
            int right = Screen.PrimaryScreen.WorkingArea.Right;
            int bottom = Screen.PrimaryScreen.WorkingArea.Bottom;
                       
            return _ImageSearchArea(findImage, resultPosition, 0, 0, right, bottom, tolerance);
        }

        public static Point _ImageSearchArea(string findImage, bool resultPosition, int x1, int y1, int right, int bottom, int tolerance) {
                new Thread(delegate()
                {
                    try
                    {
                        string result = ImageSearch(x1, y1, right, bottom, "*100" + findImage);
                    }
                    catch (SEHException sehException)
                    {
                        int errcode = sehException.ErrorCode;   
                        throw sehException;
                    }
                }).Start();
      
            Point imagelocation = new Point();
            
            //imagelocation.X = Convert.ToInt32(arr[2]);
            //imagelocation.Y = Convert.ToInt32(arr[3]);

           //if (resultPosition)
            //{
            //    imagelocation.X += Convert.ToInt32(arr[4]) / 2;
            //    imagelocation.Y += Convert.ToInt32(arr[5]) / 2;
            //}
           return imagelocation;
        }