CODEWITHSUNDEEP
c#code-analysis
Niel de Wet
Niel de Wet

Reputation: 8398

False CA1812 warning : "internal class that is apparently never instantiated..."

I am getting a code analysis warning that seems to be a false-positive.

CA1812 : Microsoft.Performance : 'MyClass.MyPrivateClass' is an internal class that is apparently never instantiated. If so, remove the code from the assembly. If this class is intended to contain only static methods, consider adding a private constructor to prevent the compiler from generating a default constructor.

How do I get rid of this warning? I prefer to not suppress warnings unless I am sure I couldn't avoid it otherwise.

The classes look like this:

namespace Some.Namespace
{
    public class MyClass
    {
        private class MyPrivateClass
        {
            public int Id { get; set; }
            public ModelObject { get; set; }
        }
    }
}

I use it like this:

private IQueryable<MyPrivateClass> GetMyPrivateClasses()
{
    return this.Repository().All()
        .Select(m => new MyPrivateClass { Id = m.Id, ModelObject = m };
}

Does this usage not count as instantiation?

Upvotes: 17

Views: 12489

Answers (4)

Edward Olamisan
Edward Olamisan

Reputation: 891

The only thing that worked for me was adding propertygroup and nowarn to the project in question:

  <PropertyGroup>
    <NoWarn>CA1812</NoWarn>
  </PropertyGroup>

Upvotes: 0

pera
pera

Reputation: 21

FYI there is a new documentation page for this warning:

https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/quality-rules/ca1812

Instantiation of classes is not always recognized by analyzers.

Suppress this warning, if justified:

[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1812:AvoidUninstantiatedInternalClasses", Justification = "generic/late bound/reflection")]

Happens especially in Net.Core.

Upvotes: 1

Miguel Domingues
Miguel Domingues

Reputation: 440

Change your class to internal or public, that solves the problem. Anyway, you can extract your inner class from the outer class...

Upvotes: -1

Marc Gravell
Marc Gravell

Reputation: 1062895

I guess it is examining the IL; and genuinely - that IL does not ever contain a new MyPrivateClass instruction - because that statement is presumably running against IQueryable<T>, hence that lambda is an expression tree. It will contain some Expression.New, and some typeof(MyPrivateClass) - but no new MyPrivateClass.

In this case, the error is misleading. Simply suppress it.

Upvotes: 22

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