CODEWITHSUNDEEP
c#autofac
Matt Fitzmaurice
Matt Fitzmaurice

Reputation: 1416

Empty string passed to constructor via Autofac instead of expected value

I'm new to autofac, so sorry if i'm asking a dumb question. I'm having trouble passing an argument to a constructor

I've got the following Interface and class:

interface IMyService
{
    string GetVersion();
}

class MyService : webService, IMyService
{
    public MyService(string serverPath)
        : base(serverPath){}

    public string GetVersion() { return "1.0"; }
}

This is how i'm setting things up:

public static class AutofacManager
{
    public static IContainer Container { get; set; }

    public static void Configure()
    {
        var builder = new ContainerBuilder();
        builder.RegisterType<string>();
        builder.Register<MyService>((c, p) => new MyService(c.Resolve<string>(p))).As<IMyService>();
        Container = builder.Build();
    }
}

and i'm using the object like this:

var ws = Container.Resolve<IMyService>(Autofac.TypedParameter.From<string>(url));
var ver = ws.GetVersion();

The problem is that an empty string is passed to the constructor. I expected it to pass the url varialbe.

Help? Thanks

Upvotes: 1

Views: 674

Answers (1)

mrvux
mrvux

Reputation: 8953

Ok first thing is you try to register the string type, which is not needed (you can remove that lineà.

You can modify your delegate to match the following:

builder.Register((c, p) =>
{
    var url = p.Named<string>("url");
    return new MyService(url);
}).As<IMyService>();

You add a named parameter so you can specify url at resolve time.

The As will make sure to register as interface (otherwise you register concrete class).

Then to Resolve your object:

string MyUrl = "";
var ws = Container.Resolve<IMyService>(new NamedParameter("url", MyUrl));

EDIT: Instead of having to resolve with url everytime, you can also allow to set url at register time, eg:

string MyUrl = "hello";
builder.RegisterType<MyService>().
WithParameter(new NamedParameter("serverPath",MyUrl)).As<IMyService>();

Then, you can resolve as:

var ws = Container.Resolve<IMyService>();

Upvotes: 1

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