Retrieving Container Registration Information

You can retrieve a list of registrations from a container, and check if a specific registration is in the container.

This topic contains the following sections:

• Viewing the Container Registrations and Mappings
• Checking for the Existence of a Specific Registration

Viewing the Container Registrations and Mappings

The Unity container exposes the Registrations property which returns an IEnumerable list of the registrations within that container. Each registration is an instance of the ContainerRegistration class, which exposes information such as the registered type, the registration name (if any), the mapped type (if any), and the lifetime manager that the registration uses.

The following example uses this feature to display the contents of a container. It queries the Count() extension method for IEnumerable<T>, and then iterates through it displaying a list of the registrations and mappings.

void DisplayContainerRegistrations(IUnityContainer theContainer)
{
    string regName, regType, mapTo, lifetime;
    Console.WriteLine("Container has {0} Registrations:",
            theContainer.Registrations.Count());
    foreach (ContainerRegistration item in theContainer.Registrations)
    {
    regType = item.RegisteredType.Name;
    mapTo = item.MappedToType.Name;
    regName = item.Name ?? "[default]";
    lifetime = item.LifetimeManagerType.Name;
    if (mapTo != regType)
    {
        mapTo = " -> " + mapTo;
    }
    else
    {
        mapTo = string.Empty;
    }
    lifetime = lifetime.Substring(0, lifetime.Length - "LifetimeManager".Length);
    Console.WriteLine("+ {0}{1}  '{2}'  {3}", regType, mapTo, regName, lifetime);
    }
}

Sub DisplayContainerRegistrations(ByVal theContainer As IUnityContainer)
    Dim regName As String, regType As String, _
            mapTo As String, lifetime As String
    Console.WriteLine("Container has {0} Registrations:", _
            theContainer.Registrations.Count())
    For Each item As ContainerRegistration In theContainer.Registrations
        regType = item.RegisteredType.Name
        mapTo = item.MappedToType.Name
        regName = If(item.Name, "[default]")
        lifetime = item.LifetimeManagerType.Name
        If mapTo <> regType Then
            mapTo = " -> " & mapTo
        Else
            mapTo = String.Empty
        End If
        lifetime = lifetime.Substring( _
                0, lifetime.Length - "LifetimeManager".Length)
        Console.WriteLine("+ {0}{1} '{2}' {3}", _
                regType, mapTo, regName, lifetime)
    Next
End Sub

The Name property of a ContainerRegistration instance returns null (C#) or Nothing (Visual Basic) for default (unnamed) registrations. The MappedToType property has the same value as the RegisteredType when this is a non-mapped concrete type registration (rather than a base class or interface mapped to a concrete type).

Checking for the Existence of a Specific Registration

You can also use the methods of the container to check if a specific registration or mapping exists. The IsRegistered method takes a container, a type, and optionally a registration name, and returns True or False. For example, to check if there is a registration in the container for the type MyEmailService, you would use the following code.

IUnityContainer container = new UnityContainer();
bool result = container.IsRegistered<MyEmailService>();

Dim container As IUnityContainer = New UnityContainer()
Dim result As Boolean = container.IsRegistered(Of MyEmailService)()

This will return True if there is a default (unnamed) registration for the MyEmailService type. If you want to check for the presence of a named registration, you simply specify the name in the call to the IsRegistered method, as shown in the following example.

bool result = IsRegistered<MyEmailService>("EMailHandler");

Dim result As Boolean = IsRegistered(Of MyEmailService)("EMailHandler")

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