c# - Why does my code throw an exception when I try to scan using WIA? -

i'm making application on c# winforms scans documents , places them picturebox, when attempt scan throws exception saying "object reference not set instance of object" , not allow me continue, stack trace below;

to clarify, work project in case gets alarmed of class names.

abdesktop.exe!abdesktop.frmcreditcards.scansetup() line 39  c#     abdesktop.exe!abdesktop.frmcreditcards.scanfrontbtn_click(object sender, system.eventargs e) line 94 + 0x8 bytes    c#     [external code]      abdesktop.exe!abdesktop.program.main(string[] args) line 26 + 0x20 bytes    c#     [external code]  

this code causing issue;

 public void scansetup()  {      wia.commondialog dialog = new wia.commondialog();      imagefile scannedimage=null;       scannedimage = dialog.showacquireimage(          wiadevicetype.scannerdevicetype,          wiaimageintent.unspecifiedintent,          wiaimagebias.maximizequality,          formatid.wiaformatpng,          true, true, false);      scannedimage.savefile("c:/users/reece.cottam/pictures");  } 

and button executes above code when click event fired

private void scanfrontbtn_click(object sender, eventargs e) {     scansetup();     imagefile if = new imagefile();     frontscanbox.image = if.loadfile("scannedimage.png"); } 

any appreciated.

edit line of code causing error scannedimage.savefile

without information line throws exception, guess it's line scannedimage.savefile(...); since documentation commondialog.showacquireimage(...) states null value may returned. in case, when try operate on variable scannedimage, attempting operate on null reference.