Set timestamp on read-only file on Windows

Setting the timestamp on a file with the read-only attribute now succeeds on Windows and no longer throws an exception.

Old behavior

Prior to .NET 6 servicing releases, setting the timestamp on a read-only file on Windows resulted in an UnauthorizedAccessException.

New behavior

Starting in .NET 6.0.2, setting the timestamp on a read-only file on Windows succeeds.

Version introduced

.NET 6.0.2 (servicing release)

Type of breaking change

This change can affect binary compatibility.

Reason for change

Customers gave feedback that they expected setting the timestamp on a read-only file to succeed. This change also makes the Windows behavior consistent with Linux. Finally, the behavior was unintentional, caused by a bug.

Recommended action

It is unlikely that existing code expects setting the timestamp on a read-only file to fail. However, if your code expects it to fail, add a check for the read-only attribute using File.GetAttributes(String) before attempting to set the timestamp.

Affected APIs

• System.IO.File.SetCreationTime(String, DateTime)
• System.IO.File.SetCreationTimeUtc(String, DateTime)
• System.IO.File.SetLastAccessTime(String, DateTime)
• System.IO.File.SetLastAccessTimeUtc(String, DateTime)
• System.IO.File.SetLastWriteTime(String, DateTime)
• System.IO.File.SetLastWriteTimeUtc(String, DateTime)