Default parameter for CancellationToken

Question

I have some async code that I would like to add a CancellationToken to. However, there are many implementations where this is not needed so I would like to have a default parameter - perhaps CancellationToken.None. However,

Task<x> DoStuff(...., CancellationToken ct = null)

yields

A value of type '' cannot be used as a default parameter because there are no standard conversions to type 'System.Threading.CancellationToken'

and

Task<x> DoStuff(...., CancellationToken ct = CancellationToken.None)

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

Is there any way to have a default value for CancellationToken?

Answer 1

It turns out that the following works:

Task<x> DoStuff(...., CancellationToken ct = default(CancellationToken))

...or:

Task<x> DoStuff(...., CancellationToken ct = default) // C# 7.1 and later

which, according to the documentation, is interpreted the same as CancellationToken.None:

You can also use the C# default(CancellationToken) statement to create an empty cancellation token.