How to use Environment.NewLine as an optional parameter default value

Question

I prefer Environment.NewLine over "\r\n" whenever possible, even though this project is Windows-only. I was wondering if there was a way to use it as a default value of an optional parameter.

Consider the extension method

public static string ToSummaryString<T>(
    this IEnumerable<T> items, 
    string delimiter = Environment.NewLine)

and the compile time error

Default parameter value for 'delimiter' must be a compile-time constant

I tried using parameter attributes too, with a similar fate

public static string ToSummaryString<T>(
    this IEnumerable<T> items, 
    [Optional, DefaultParameterValue(Environment.NewLine)] string delimiter)

An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type

So is there any workaround? Or are my only options to hard-code it to "\r\n", or make it required?

Can you use null as the default value and switch to Environment.NewLine inside the method when the argument is null? — Progman
You can always do it "the old way": write 2 methods; one with the delimiter and one without. — Dennis_E

Salah Akbari Salah Akbari · Accepted Answer · 2018-12-18T21:04:32

You can replace your default value with Null and then use null-coalescing operator, inside your method. Something like this:

public static string ToSummaryString<T>(this IEnumerable<T> items, string delimiter = null)
{
    var realDelimiter = delimiter ?? Environment.NewLine;
}

As an alternative, you can also use Method-Overloading, as @Dennis_E also mentioned: write 2 methods; one with the delimiter and one without.

How to use Environment.NewLine as an optional parameter default value

2 Answers