Today, small remark about a code mistake. Tools like Rider or R# shows that mistake but bare VS does not (IIRC) so I still sometimes see such slip in PR reviews.
LINQ's OrderBy followed by another OrderBy doesn't sort by first expression and then by the second one. It only will use the second one. If we need more columns in the sorting we need to incorporate ThenBy, even multiple times.
// ❌ this is not correct
var sorted = data
.OrderBy(d => d.CreatedOn)
.OrderBy(d => d.Country)
.ThenBy(d => d.Region);// ✅ do this instead
var sorted = data
.OrderBy(d => d.CreatedOn)
.ThenBy(d => d.Country)
.ThenBy(d => d.Region);