Iv recently changed department at work and after working with Java for 5 years I'm suddenly thrown into C# code. Now most of it is similar to Java but there seems to be a lot more DI going on.

The code is part of a ASPNet core project and there is one thing I don't get. The controller class which is about 10 000 lines of code contains many methods with the following "in parameters":

StreamingUploadMapper([FromServices] EsiDecryptClient esiDecryptClient, [FromServices] IStorageHandler storageHandler)

My question is what is this? Is it auto injected (DI) or must I send these params in when I make a request? I also googled FromServices and it seems its used for DI to avoid using "new"? Other than that I don't even really understand what it is for.

Any help would be much appreciated.

CodePudding user response：

My question is what is this? Is it auto injected (DI)

Yes, that's what it is. You use [FromServices] when you want to inject a service only on a particular action, rather than for the entire Controller. On a 10k LOC Controller, that kind of makes sense (though I'm surprised DI is used with such a beast).