Uploading files to sharepoint library using C#.Net code

I want to upload the file to the form library in the sharepoint(I am able to do it).
now after editing i want to reload the file to the form library again.In this case i am getting error as 

Microsoft.SharePoint.SPException: The file "" is checked out or locked for editing by CCC\12345. ---> System.Runtime.InteropServices.COMException (0x81020036): The file "" is checked out or locked for editing by CCC\12345.
In C#.net, how to check to overwrite and checkin the file?