Contextual bindings with Ninject 2.0

问题:

In Ninject 1.0 I had following binding definitions:

Bind<ITarget>().To<Target1>().Only(When.Context.Variable("variable").EqualTo(true));
Bind<ITarget>().To<Target2>();

Given such bindings I had calls:

ITarget target = kernel.Get<ITarget>(With.Parameters.ContextVariable("variable", true));
ITarget target = kernel.Get<ITarget>(With.Parameters.ContextVariable("variable", false));

First call was resolved to instance of Target1, second call was resolved to instance of Target2.

How to translate this into Ninject 2.0?

回答1:

You can use metadata,

[Fact]
public void MetadataBindingExample()
{
    string metaDataKey = "key";
    kernel.Bind<IWeapon>().To<Shuriken>().WithMetadata(metaDataKey, true);
    kernel.Bind<IWeapon>().To<Sword>().WithMetadata(metaDataKey, false);
    kernel.Bind<IWeapon>().To<Knife>();

    var weapon = kernel.Get<IWeapon>(metadata => metadata.Has(metaDataKey) && metadata.Get<bool>(metaDataKey));
    Assert.IsType<Shuriken>( weapon );

    weapon = kernel.Get<IWeapon>(metadata => metadata.Has(metaDataKey) && !metadata.Get<bool>(metaDataKey));
    Assert.IsType<Sword>(weapon);

    weapon = kernel.Get<IWeapon>(metadata => !metadata.Has(metaDataKey));
    Assert.IsType<Knife>(weapon);
}