xna - imageItem returning null in c# -

i have line of code ment extract image data item, code skips imageitem = null. cause of this?

foreach (layer layer in level.layers) {     foreach (item item in layer.items)     {         imageitem imageitem = item imageitem;         if (imageitem != null)         {             texture2d texture = imageitem.texture;             imageitemlist[iimageitemnum].itemtexturedatalist[0] =                      new color[imageitem.texture.width * imageitem.texture.height];             imageitem                 .texture                 .getdata(imageitemlist[iimageitemnum]                 .itemtexturedatalist[0]);             iimageitemnum++;         }     } } 

the as operator cast operation. however, if conversion isn't possible, returns null instead of raising exception

so if current item in layer.items not imageitem null assigned imageitem in line

imageitem imageitem = item imageitem;