C
C#

How to let compiler know that List is not null?

How to let compiler know that List is not null?

Nnelsonprsousa11/21/2023
Hi community! I have the following extension method:, which checks if the source is not null and if it contains any elements: public static bool SafeAny<T>(this IEnumerable<T> source) => source != null && source.Any(); I'd like to inform the compiler that, when returning true, the source is not null. Is this possible to achieve with C#? Thank you!
No description
Nnelsonprsousa11/21/2023
Note: I know we could use myList!, but that's developer work instead of compiler actually knowing šŸ˜‡
TThinker11/21/2023
Where are you getting myList from? The compiler is likely inferring this for a reason
JJoschi11/21/2023
I think you are looking for the NotNullWhenAttribute This is how the .NET TryParse methods are implemented.
c#
// Determines whether a String represents true or false.
//
public static bool TryParse([NotNullWhen(true)] string? value, out bool result) =>
TryParse(value.AsSpan(), out result);
c#
// Determines whether a String represents true or false.
//
public static bool TryParse([NotNullWhen(true)] string? value, out bool result) =>
TryParse(value.AsSpan(), out result);
It says: If this method returns true this parameter won't be null.
TThinker11/21/2023
oh, read the question wrong, sorry. yeah this is correct
Nnelsonprsousa11/23/2023
That was it, thank you!

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How to let compiler know that List is not null?

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