Solved: Cannot perform '<' operation on System.DateTime and System.Double.

if you check the string you build, you would see that it would be a "math expression"

you need to put quotes:

 dvholidays = New DataView(dtholidays, "Date < '" & enddate.AddDays(1).ToShortDateString & "' and Date > '" & startdate.AddDays(-1).ToShortDateString & "' ", "", DataViewRowState.CurrentRows)

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this will resolve the error, but it will eventually result in bad results if the comparison of the values is not "expected".

see this article:
https://www.experts-exchange.com/Database/Miscellaneous/A_1499-DATE-and-TIME-don%27t-be-scared-and-do-it-right-the-first-time.html
it's not about data views, so it won't show the relevant solutions, but ideas to think at least.
as I indicated in your previous question, you may need to solve this differently.
make so that the "date" field in the dataset is returned as string in the format 'YYYYMMDD' to make your > and < conditions to work ...

Cannot perform '&lt;' operation on System.DateTime and System.Double.

Cannot perform '<' operation on System.DateTime and System.Double.