Problem reading cells with some types of formulas

[IsakNaslundBh]

Description:

Reading from some cells with formulas in them leads to a crash in the closed xml package when trying to access the value. By my quick investigation, it looks like accessing the Value property of the IXLCell means the cell value is re-computed making use of some mechanism in the closedXML repo, and that it fails to do so if the cell contains certain formulas.

A way around this is to instead fetch the CashedValue, or potentially just fallback to this, by first calling the TryGetValue and if that fails, fall back to the CashedValue.

Steps to reproduce:

Will produce testfile that illustrates the issue.

Expected behaviour:

For sheets with formulas to pull, giving back the value in the cell, could be pre-computed, or live computed.

Test file(s):

Will raise PR and provide there.