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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.

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.

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.

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.

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; } 

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.