C#•2y ago

❔ CSharp [] attribute help

Hi! sorry for the basic question, but I need a not so technical and more casual explanation about (I think it is) the call of attributes through brackets [] Like this code:

[ApiController]// What is this? What attribute does he call? where from?
[Route("[controller]")] 

public class WeatherForecastController : ControllerBase
{

[ApiController]// What is this? What attribute does he call? where from?
[Route("[controller]")] 

public class WeatherForecastController : ControllerBase
{

5 Replies

Angius•2y ago

Those are attributes, they don't call anything They're just metadata that other code can use

peladodocineroOP•2y ago

Ah Thanks you

mtreit•2y ago

While I generally agree with this, we have a ton of code in some attributes we define that gets executed via the attribute constructor and calls all sorts of other code to set up a bunch of data structures, etc. This is invoked when GetCustomAttribute is used to retrieve the attribute metadata. So depending on the code base, there can be a lot of code lurking inside attributes...it's just not executed until someone uses reflection to retrieve the attribute on something.

Angius•2y ago

I might've not been clear enough, yeah, I agree. What I meant is that just adding an attribute to a thing doesn't do anything on its own. Attributes can contain code, but something else needs to call that code.

Accord•2y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ CSharp [] attribute help