FileSystem.CopyFile IOException timing and data integrity

File Restoration Behavior

When implementing a backup restoration routine using Microsoft.VisualBasic.FileIO.FileSystem.CopyFile, the Overwrite parameter determines whether an existing destination file is replaced. If set to False and a file already exists at the target path, the method triggers an IOException.

Verification Constraints

The current documentation does not specify the exact sequence of operations regarding this exception. It is unclear if the IOException is raised during a pre-check phase before any I/O occurs, or if it occurs after a failed attempt to open the destination file for writing.

Furthermore, the method provides no native mechanism to verify that the recovered data matches the source, such as a checksum or byte-count validation, leaving the integrity of the restoration to the developer's implementation.

• Does the IOException occur before or after the system attempts to access the destination file?
• Is there a documented way to ensure file integrity within the FileSystem class, or must external hashing be used?