Visual Studio中的构造函数依赖性代码段

Question

I find myself adding dependencies a lot to constructors like so:

public class SomeClass() {
    private ISomeService _service;
    private IAnotherService _anotherService;
    public SomeClass(ISomeService service, IAnotherService anotherService) {
        _service = service;
        _anotherService = anotherService;
    }
}

They're quite tedious to write, I've been looking for code snippets in visual studio to automatically add one to the constructor but haven't found one.

What I want is:

• When adding a dependency to a constructor some snippet automatically creates a local variable and assigns to it.

OR

• Add a private variable and then some snippet automatically adds it to the constructor and assigns it to the local variable.

Answer 1

If you have R# you can enter the field declarations and then highlight them and hit Alt-Enter which will give you the option to generate the constructor and field assignments.

Answer 2

If you don't have Resharper, you can add the parameter on the constructor, write the assignament to an unexisting property and hit CTRL+. . This will prompt you with the options to automatically create a property or field for you.

For example, you have this class:

public class MyClass 
{ 
    public MyClass()
    { 
    }
}

You then add the parameter to the constructor, and the assignament:

public class MyClass 
{ 
    public MyClass(IDependency myDependency)
    { 
         this.myDependency = myDependency;
    }
}

And hit CTRL+. while on the asignament line, and select create field, and you'll get this:

public class MyClass 
{         
    IDependency myDependency;

    public MyClass(IDependency myDependency)
    { 
         this.myDependency = myDependency;
    }
}

Answer 3

I don't know about previous versions, but in vanilla Visual Studio 2017, you can actually add a constructor parameter

public SomeClass(ISomeService service)
{ 
}

Then put your cursor on service and from "Quick actions" you can chose Introduce and initialize field _someService which will do what you want :

private readonly ISomeService _someService;

public SomeClass(ISomeService service)
{ 
    _someService = service;
}

Answer 4

You can easily add code snippets as you like, defining it in XAML and adding it the editior, you can use place holders like "class name" to use it as a constructor for example, and then place your variables in it as static text

I don't want to write the code because it's duplicated you can check out how to do it here: https://msdn.microsoft.com/en-us/library/ms242312.aspx?f=255&MSPPError=-2147217396

you can also see this question: How can I automatically generate a constructor that receives and stores services for free?

Answer 5

what you are trying to do with the ISomeService and IAnotherService is to do dependency inversion.

I would strongly recommend you combine this with a dependency injection framework. There are many available but one i would recommend is MEF. MEF is build into the .net framework. For example your code would look like this with MEF

[Export(typeof(ISomeService))]
public class SomeService : ISomeService {
}


public class SomeClass {

   [Import]
   public ISomeService SomeService {get; set;}

   [Import]
   public IAnotherService AnotherService {get; set;}

}

Now MEF will actually ensure your SomeService and AnotherService Properties are filled when your class is created. It will construct (if needed) a instance of SomeService, fill all it's dependencies and put it in the right property. You can even control if you want your services instantiated as singletons or as a new service instance each time you need one.

for more details on MEF you can look here https://msdn.microsoft.com/en-us/library/ee155691(v=vs.110).aspx

This should avoid writing the many constructors that do nothing other than initializing services.

Answer 6

Telerik's JustCode can do exactly what you need.
if you have an unused argument in the constructor you can create a field and initialise it. http://www.telerik.com/products/justcode/quick-fixes.aspx