C# best practices
I've got an issue similar to the theoretical situation below and am looking to follow the industry best practice.

Use case:   
A user may tip the staff based on a flat amount or a percentage of services rendered.

UI:   
The user would be given a dropdown asking percent or $ and a value. The user would then be given a textbox to enter an amount.

Question:    
Underneath the hood, would you have a two separate values - one for percent and one for dollars, or would you just have one value whose meaning is determined by the value of an enum? (Or would you do something else?)
C# best practices
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I've got an issue similar to the theoretical situation below and am looking to follow the industry best practice.

Use case:   
A user may tip the staff based on a flat amount or a percentage of services rendered.

UI:   
The user would be given a dropdown asking percent or $ and a value. The user would then be given a textbox to enter an amount.

Question:    
Underneath the hood, would you have a two separate values - one for percent and one for dollars, or would you just have one value whose meaning is determined by the value of an enum? (Or would you do something else?)