ActivatorUtilities.CreateInstance Throwing InvalidOperationException in .NET 8

[eajhnsn1]

Description

After upgrading to .NET 8, ActivatorUtilties.CreateInstance is throwing InvalidOperationException when the following conditions are met

1. The type being activated has multiple constructors, one of which is the default constructor
2. There are no constructor parameters passed to ActivatorUtilties.CreateInstance, ie. Type.EmptyTypes

Reproduction Steps

    internal class Program
    {
        static void Main(string[] args)
        {
            _ = ActivatorUtilities.CreateInstance(new EmptyServiceProvider(), typeof(TestClass));
        }

        class TestClass
        {
            public TestClass()
            {
                    
            }
    
            /* Comment out this constructor and the call will succeed */
            public TestClass(int value)
            {

            }
        }

        class EmptyServiceProvider : IServiceProvider
        {
            public object? GetService(Type serviceType)
            {
                return null;
            }
        }
    }    

Expected behavior

Call the default constructor.

Actual behavior

Throwing InvalidOperationException, with message "Multiple constructors accepting all given argument types have been found in type ..."

Regression?

Yes this worked in .NET 7 and prior.

Known Workarounds

No response

Configuration

No response

Other information

No response

[ghost]

Tagging subscribers to this area: @dotnet/area-extensions-dependencyinjection
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Description

After upgrading to .NET 8, ActivatorUtilties.CreateInstance is throwing InvalidOperationException when the following conditions are met

1. The type being activated has multiple constructors, one of which is the default constructor
2. There are no constructor parameters passed to ActivatorUtilties.CreateInstance, ie. Type.EmptyTypes

Reproduction Steps

    internal class Program
    {
        static void Main(string[] args)
        {
            _ = ActivatorUtilities.CreateInstance(new EmptyServiceProvider(), typeof(TestClass));
        }

        class TestClass
        {
            public TestClass()
            {
                    
            }
    
            /* Comment out this constructor and the call will succeed */
            public TestClass(int value)
            {

            }
        }

        class EmptyServiceProvider : IServiceProvider
        {
            public object? GetService(Type serviceType)
            {
                return null;
            }
        }
    }    

Expected behavior

Call the default constructor.

Actual behavior

Throwing InvalidOperationException, with message "Multiple constructors accepting all given argument types have been found in type ..."

Regression?

Yes this worked in .NET 7 and prior.

Known Workarounds

No response

Configuration

No response

Other information

No response

Author:	eajhnsn1
Assignees:	-
Labels:	untriaged, area-Extensions-DependencyInjection, needs-area-label
Milestone:	-

[mikechristiansenvae]

I believe you're supposed to be using ActivatorUtilitiesConstructorAttribute to indicate which constructor to use, if there is more than one.

Although it does seem that the behavior of this method was changed for .NET 8 in PR #75846

[eajhnsn1]

I'll also add that this occurs when the container does not support using IServiceProviderIsService. The exception is being thrown from TryFindMatchingConstructor.

[buyaa-n]

CC @steveharter

[ghost]

Added needs-breaking-change-doc-created label because this issue has the breaking-change label.

1. Create and link to this issue a matching issue in the dotnet/docs repo using the breaking change documentation template, then remove this needs-breaking-change-doc-created label.

Tagging @dotnet/compat for awareness of the breaking change.

[steveharter]

Although it does seem that the behavior of this method was changed for .NET 8 in PR #75846

Correct; I verified this issue was due to the check\usage of IServiceProviderIsService in PR #75846.

Assuming we make no changes, the workarounds are:

• The service provider must implement IServiceProviderIsService in order to tell whether or not a given parameter type is registered as a service.
• Use [ActivatorUtilitiesConstructor] on the appropriate preferred constructor.

The original PR was marked with the breaking-change with the doc here: dotnet/docs#31785.

[steveharter]

Closing as by design based on the breaking change notification linked above.