The easiest way to Convert a Unix timestamp to a DateTime or DateTimeOffset is to use the methods FromUnixTimeSeconds for seconds or FromUnixTimeMilliseconds for milliseconds. However this method only exists on the DateTimeOffset struct, however you can easily get a DateTime from a DateTimeOffset by calling the .DateTime or .UtcDateTime method on your DateTimeOffset instance.
An example of FromUnixTimeSeconds - and what you are likely looking for - can be seen here:
DateTimeOffset dateTimeOffset =
DateTimeOffset.FromUnixTimeSeconds(1669321628);
Here is an example of FromUnixTimeMilliseconds:
DateTimeOffset dateTimeOffset =
DateTimeOffset.FromUnixTimeMilliseconds(1669321628392);
Here is an example of creating a DateTime based on a unix timestamp:
DateTime dateTimeOffset =
DateTimeOffset.FromUnixTimeSeconds(1669321628)
.DateTime;
If you want to get a unix timestamp from a DateTime or DateTimeOffset (the reverse of the above), check out my other post on how to do this in-depth. In short you can use .ToUnixTimeSeconds and .ToUnixTimeMilliseconds to achieve this.
I hope you found this post helpful, feel free to leave a comment down below!