dotnet/Documentation/compatibility/contentdisposition-datetimes-returns-slightly-different-string.md

## ContentDisposition DateTimes returns slightly different string

### Scope
Minor

### Version Introduced
4.6

### Source Analyzer Status
Available

### Change Description

String representations of
<xref:System.Net.Mime.ContentDisposition?displayProperty=name>'s have been
updated, beginning in 4.6, to always represent the hour component of a
<xref:System.DateTime?displayProperty=name> with two digits. This is to comply
with [RFC822](http://www.ietf.org/rfc/rfc0822.txt) and
[RFC2822](http://www.ietf.org/rfc/rfc2822.txt). This causes
<xref:System.Net.Mime.ContentDisposition.ToString>
to return a slightly different string in 4.6 in scenarios where one of the
disposition's time elements was before 10:00 AM. Note that
ContentDispositions are sometimes serialized via converting them to strings,
so any <xref:System.Net.Mime.ContentDisposition.ToString>
operations, serialization, or GetHashCode calls should be reviewed.

- [ ] Quirked
- [ ] Build-time break

### Recommended Action

Do not expect that string representations of ContentDispositions from different
.NET Framework versions will correctly compare to one another. Convert the
strings back to ContentDispositions, if possible, before conducting a
comparison.

### Affected APIs
* `M:System.Net.Mime.ContentDisposition.ToString`
* `M:System.Net.Mime.ContentDisposition.GetHashCode`

### Category
Networking

<!-- breaking change id: 78 -->