Can I use a TimeSpan as an optional parameter with a default value?

Question

The answer for C# 4.0 doesn't work anymore. <-- (Sorry, this is wrong)

How can I use a TimeSpan as an optional parameter with default value?

public static Foo(string myString, TimeSpan maxWait = TimeSpan.FromSeconds(1))
{
    // do something
}

With this code I get the error:

default parameter must be a compile-time constant

What do you mean by "the answer for C# 4 doesn't work anymore"? — Evk, Apr 13 '17 at 08:26
@EvK I missed one `?` from an other SO example. Therefore it didn't work. :/ Therefore I close this post. — kame, Apr 13 '17 at 08:30

score 11 · Accepted Answer · edited Apr 13 '17 at 08:30

This has never worked in any C# version. Defaults must be constants. You have to create an overload to default the value, or make it nullable and default it if the value is null.

Option 1:

public static Foo(string myString)
{
    Foo(myString, TimeSpan.FromSeconds(1));
}

public static Foo(string myString, TimeSpan maxWait)
{
    // do something
}

Option 2:

public static Foo(string myString, TimeSpan? maxWait = null)
{
    TimeSpan maxWaitNotNull = maxWait ?? TimeSpan.FromSeconds(1);
    // do something
}

Can I use a TimeSpan as an optional parameter with a default value?

1 Answers1