CODEWITHSUNDEEP
c#optional-parameterscompile-time-constant
djv
djv

Reputation: 15774

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

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?

Upvotes: 2

Views: 441

Answers (2)

Salah Akbari
Salah Akbari

Reputation: 39966

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.

Upvotes: 2

Fletchius
Fletchius

Reputation: 460

It seems to me the best way to do this would be to have the default value be null, then check for that value in the method. If the parameter is null, set the default value to "\r\n." Better yet, have that default value be in a resource file so that you can change it as needed without having to recompile the app. (Putting the value in a config file works as well, of course)

Upvotes: 0

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