Use 'in' and 'ref' for value types where applicable

[Pankraty]

Do you want to request a feature or report a bug?

• Bug
• Feature
• Enhancement

Version of ClosedXML

e.g. 0.93

What is the current behavior?

With a new approach to styles and addresses processing structs became widely used in ClosedXML.

C# 7.2 introduces new features regarding value types (https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-7-2#reference-semantics-with-value-types) so we can have some use of them after CloseXML is upgraded to C# 7.2. Specifically, marking input parameters with in keyword looks promising for me - on the synthetic benchmark I achieved about 34% of performance improvement with this.

For now, we can park this issue.

[igitur]

Does it work on dotnet40?

…

[Pankraty]

Yes