Optional parameters “must be a compile-time constant”

Question

I have a class divided in two partial files, like this:

public partial class PersonRepository : BaseRepository
{
    public static readonly str         


        

Answer 1

You must declare your ColumnID as const.

The static readonly string will be instantiated when the class is first accessed in your code, and you could also initialize it with the return value of a static method, so it's not a compile-time constant for the compiler (even if in this case it obviously is for a person reading the code).