Hi @ashrafhuss96118
Try taking some pictures and then download them to a computer and check if there's a white line showing in the picture as well.
''If not'' then most probably there are problem in the LCD screen.
''If there is'' then it could be a problem in the CCD sensor.
Here's the [https://elektrotanya.com/sony_dsc-w310_ver-1.0_sm.pdf/download.html|service manual] for the camera.
Go to p.7/12 to view the disassembly procedure.
On p.8/12 it shows how to remove the LCD screen. Search online for ''1-811-083-11,'' to find suppliers for the LCD screen that suit you best. This is the Sony part number (part #54) for the LCD screen.
On p.10/12 it shows the CCD assembly see part #153.