Passing parameters to constructors using Autofac

Question

I\'m very new to autofac so it\'s possible that I\'m completely misusing it.

Let\'s say I have a class that has this structure:

public class HelperClass          


        

Answer 1

There are two ways to pass parameters in Autofac:

When you are registering the component:

When you register components, you have the ability to provide a set of parameters that can be used during the resolution of services based on that component. Autofac offers several different parameter matching strategies:

• NamedParameter - match target parameters by name
• TypedParameter - match target parameters by type (exact type match required)

• ResolvedParameter - flexible parameter matching

  // Using a NAMED parameter:
  builder.RegisterType()
     .As()
     .WithParameter("configSectionName", "sectionName");// parameter name, parameter value. It's the same of this: new NamedParameter("configSectionName", "sectionName")
  
  // Using a TYPED parameter:
  builder.RegisterType()
     .As()
     .WithParameter(new TypedParameter(typeof(string), "sectionName"));
  
  // Using a RESOLVED parameter:
  builder.RegisterType()
     .As()
     .WithParameter(
       new ResolvedParameter(
         (pi, ctx) => pi.ParameterType == typeof(string) && pi.Name == "configSectionName",
         (pi, ctx) => "sectionName"));
  

  NamedParameter and TypedParameter can supply constant values only.

  ResolvedParameter can be used as a way to supply values dynamically retrieved from the container, e.g. by resolving a service by name.

In case you want to pass as parameter a service that is already registered, eg, IConfiguration, you can resolve the parameter as I show below:

    builder.RegisterType()
           .As()
           .WithParameter((pi, ctx) => pi.ParameterType == typeof(IConfiguration) && pi.Name == "configuration",
                          (pi, ctx) => ctx.Resolve());

When you are resolving the component:

One way to pass parameter at runtime in Autofac is using the Resolve method. You could create a class like this:

public class ContainerManager
{
  public IContainer Container {get;set;}
  //...
  public T[] ResolveAllWithParameters(IEnumerable parameters)
  {
    return Container.Resolve>(parameters).ToArray();
  }
}

Parameter is an abstract class that belongs to Autofac, you can use the NamedParameter class to pass the parameters that you need. You can use the ContainerManager class as I show below:

    public T[] ResolveAllWithParameters(IDictionary parameters )
    {
        var _parameters=new List();
        foreach (var parameter in parameters)
        {
            _parameters.Add( new NamedParameter(parameter.Key, parameter.Value));
        }
        return ContainerManager.ResolveAllWithParameters(_parameters);
    }

This way you can pass the parameters at runtime using a Dictionary when you are resolving an specific component.

Using an Extension Method could be even more simple:

public static class ContainerExtensions
{
    public static T[] ResolveAllWithParameters(this IContainer Container, IDictionary parameters)
    {
        var _parameters = new List();
        foreach (var parameter in parameters)
        {
            _parameters.Add(new NamedParameter(parameter.Key, parameter.Value));
        }
        return Container.Resolve>(_parameters).ToArray();
    }
}