I try to avoid using custom attributes to configure things like business logic because they struggle to account for interactions between members. Attributes have no affordance for lambdas, delegates, method references, etc. You would need a separate piece of logic that interprets the primitive attribute data in order to provide any emergent properties between members.
A better approach is often to expose some abstract/interface member that allows for the implementation to define its logic using something like a fluent-style contract. In this arrangement you can pass the type itself as an argument to a lambda making it trivial to define logic that should execute over many members at once. Debugging this also tends to be more pleasant. AspNetCore startup code, LINQ and EF are good examples.
Attributes are useful for things that are definitely pure data and only when the information fully belongs to the thing being annotated regardless of context of use. The moment some kind of per-member custom logic is needed it's no longer appropriate. I think things like [Authorize] are borderline. [JsonIgnore] seems like a good attribute to me.
I would expect DLL parsing to be a one-off cost at assembly load time. Certainly that handles all the stuff detailed under "Assembly resolution". Assembly resolution is also recursive, so I would expect that to simplify "type tree traversal" by pre-stuffing all the types into a Dictionary.
That also necessarily has the parser for all the "System.Int32, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" machinery.
>> "While C# does not support types with weird symbols, it is possible to have type names with spaces, commas, brackets, unprintable characters, and more. This is also heavily (ab)used by code obfuscators."
.. hmm. I didn't know that.
I will note that there is a milder version of this problem which you might encounter if you're trying to write a dotnet source generator, which is run inside the Roslyn compiler. You then need to remember that the types in the code being compiled are not directly visible from reflection, you have to ask the compiler to look them up for you in the parsed data.
These cases are easy:
- types in the netstandard2.0 standard library
- types in the assembly currently being compiled
This case is not:
- types in assemblies in the same project which the current assembly depends on
I ended up avoiding handling that at all. It does set some limits on what is easily done with source generators.
(by the way, someone sufficiently dedicated should be able to find the corresponding Microsoft loader code: it's all in the dotnet github)
I try to avoid using custom attributes to configure things like business logic because they struggle to account for interactions between members. Attributes have no affordance for lambdas, delegates, method references, etc. You would need a separate piece of logic that interprets the primitive attribute data in order to provide any emergent properties between members.
A better approach is often to expose some abstract/interface member that allows for the implementation to define its logic using something like a fluent-style contract. In this arrangement you can pass the type itself as an argument to a lambda making it trivial to define logic that should execute over many members at once. Debugging this also tends to be more pleasant. AspNetCore startup code, LINQ and EF are good examples.
Attributes are useful for things that are definitely pure data and only when the information fully belongs to the thing being annotated regardless of context of use. The moment some kind of per-member custom logic is needed it's no longer appropriate. I think things like [Authorize] are borderline. [JsonIgnore] seems like a good attribute to me.
.. if you're trying to parse the assemblies by hand for some reason. If you're just trying to handle them with reflection none of this is an issue.
> If you're just trying to handle them with reflection none of this is an issue
But maybe indicates on how expensive that reflection call can be? Reading multiple .dlls ?
I would expect DLL parsing to be a one-off cost at assembly load time. Certainly that handles all the stuff detailed under "Assembly resolution". Assembly resolution is also recursive, so I would expect that to simplify "type tree traversal" by pre-stuffing all the types into a Dictionary.
That also necessarily has the parser for all the "System.Int32, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" machinery.
>> "While C# does not support types with weird symbols, it is possible to have type names with spaces, commas, brackets, unprintable characters, and more. This is also heavily (ab)used by code obfuscators."
.. hmm. I didn't know that.
I will note that there is a milder version of this problem which you might encounter if you're trying to write a dotnet source generator, which is run inside the Roslyn compiler. You then need to remember that the types in the code being compiled are not directly visible from reflection, you have to ask the compiler to look them up for you in the parsed data.
These cases are easy:
This case is not:
I ended up avoiding handling that at all. It does set some limits on what is easily done with source generators.
(by the way, someone sufficiently dedicated should be able to find the corresponding Microsoft loader code: it's all in the dotnet github)