windows phone 8 - How can I change image.source with C#? -

i'm developing windows phone app.i have image . xaml code:

<image x:name="imageclock" grid.row="1"          source="image/myimage.png" height="240" width="240"         /> 

and want change image.source code:

private void clickonbtn(object sender, eventargs e)     {             bitmapimage bm = new bitmapimage(new uri("image/darktheme.png", urikind.relativeorabsolute));             imageclock.source = bm;     } 

but when complied, imageclock.source=null , error:

an exception of type 'system.nullreferenceexception' occurred in newappver1.dll not handled in user code

your code looks ok maybe need add @ before image path handle / in code behind :

bitmapimage bm = new bitmapimage(new uri(@"image/darktheme.png", urikind.relativeorabsolute));