C# set default argument, string array (string[])

Question

I have googled some examples of C# default string parameters and found that is like this.

string Exceptions = "John"

I need to set the default value for a string [] but y haven't found how can I set an string array as default value for a C# method.

static int startapp(string Source, string Destination, string[] Exceptions = { "John", "Paul", "Mary" })
            {
                 //do something
            }

I think it's not allowed to use array literals in default parameters. I usually set them to null, and then if the value is null set the default value in the method body. — jorgonor, Oct 07 '16 at 16:00
Found [this.](http://stackoverflow.com/questions/12607146/method-parameter-array-default-value) It seems to pertain to what you're trying to do. — Matthew Beaudin, Oct 07 '16 at 16:01
That answer does look like a better way to do it. Thanks for sharing! — jorgonor, Oct 07 '16 at 16:04

score 1 · Answer 1 · edited May 23 '17 at 12:33

Sorry this had to be a comment but I don't have enough reputation to add a comment. What you are probably looking for is this answer

optional array Parameter in C# [duplicate]

it says (from the docs)

A default value must be one of the following types of expressions:

    a constant expression;

    an expression of the form new ValType(), where ValType is a value type, such as an enum or a struct;

    an expression of the form default(ValType), where ValType is a value type.

score 0 · Answer 2 · answered Oct 07 '16 at 16:02

From MSDN

A default value must be one of the following types of expressions:
- a constant expression;
- an expression of the form new ValType(), where ValType is a value type, such as an enum or a struct;
- an expression of the form default(ValType), where ValType is a value type.

In your case string[] is a reference type.
For reference types default value is always null

Visual Studio proved an explanation when you try to initialize new array as default type:

Default parameter value must be a compile-time constant

C# set default argument, string array (string[])

2 Answers2