fixed a compile-time error in type-marshalling.md

[ophura]

Summary

this change adds the out keyword to fix such compile-time error as well as inlines the variable declaration for simplicity and renames the variable from st to systemTime for both clarity and consistency.

additionally, it removes the string[] args parameter from the method signature as it isn't required and also unused.

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Internal previews

📄 File	🔗 Preview link
docs/standard/native-interop/type-marshalling.md	Type marshalling

[adegeo]

Thank you for this improvement! Do you think you can improve it some more? As it is, you can't really even copy-paste this code into a code file and have it work, there are a few errors such as it has to be declared in a partial class and a scope modifier needs to be added too.

If not, I'll take your improvement and iterate on it myself, then merge.

Thanks again!

[ophura]

I'll do just that sensei > ~ <

[adegeo]

It doesn't have to be "Main" it could just be a utility class with a method named PrintSystemTime() => Console.WriteLine... or something like that.

[ophura]

@dotnet-policy-service agree

[adegeo]

Beautiful! Thanks!

[ophura]

@adegeo I also considered other changes, regarding the first block, here's what I had in mind:

using System.Runtime.InteropServices;
using System.Runtime.InteropServices.Marshalling;

internal static partial class Interop
{
    [LibraryImport("SomeNativeLibrary.dll")]
    internal static partial int MethodA([MarshalAs(UnmanagedType.LPStr)] string parameter);

    // or

    [LibraryImport("SomeNativeLibrary.dll")]
    internal static partial int MethodB([MarshalAs(UnmanagedType.LPUTF8Str)] string parameter);

    // or

    [LibraryImport("SomeNativeLibrary.dll")]
    internal static partial int MethodC([MarshalUsing(typeof(Utf8StringMarshaller))] string parameter);

    // or

    [LibraryImport("SomeNativeLibrary.dll", StringMarshalling = StringMarshalling.Utf8)]
    internal static partial int MethodD(string parameter);
}

this is to complete the set of options originally proposed. I'd also like to note that one of the originally suggested approaches behaves differently in semantics, and that is UnmanagedType.LPStr; which relies on AnsiStringMarshaller, whereas the others use Utf8StringMarshaller for marshaling.

that is worrisome to me since the documentation states that:

if you want the string to be sent as a null-terminated UTF-8 string, you could do it like this:

followed by the code block, which again, the first method in it uses the AnsiStringMarshaller...
should MethodA be excluded in this case?

[adegeo]

@ophura would you mind opening an issue with your suggestion? This way we can tag the engineer and get a discussion going. Go to https://learn.microsoft.com/en-us/dotnet/standard/native-interop/type-marshalling (you won't see your updates just yet) and use the link at the bottom of the page to give feedback on GitHub. This will create an issue and associate with that article.

[ophura]

@adegeo done #48785