c# - 为什么不强制对泛型类型进行类约束？

Question

我有以下接口(interface)定义

public interface IEncryptor
{
    T Decrypt<T>(byte[] encryptedData) where T : class;
}

有了这个实现(应该不相关)

internal class ThingyEncryptor : IEncryptor
{
    public T Decrypt<T>(byte[] encryptedData) where T : class
    {
        var encryptedSymmetricKey = encryptedData.Take(SymmetricKeyLength).ToArray();
        var iv = encryptedData.Skip(SymmetricKeyLength).Take(IvLength).ToArray();
        var symmetricEncryptedData = encryptedData.Skip(SymmetricKeyLength + IvLength).ToArray();

        using (var rsa = _certificate.GetRSAPrivateKey())
        {
            var symmetricKey = rsa.Decrypt(encryptedSymmetricKey, RSAEncryptionPadding.Pkcs1);
            var clearData = Decrypt(symmetricEncryptedData, symmetricKey, iv);
            return JsonConvert.DeserializeObject<T>(Encoding.UTF8.GetString(clearData));
        }
    }
}

阅读 Constraints on type parameters (C# Programming Guide) , 表示:

If client code uses a type that doesn't satisfy a constraint, thecompiler issues an error

当像这样调用 Decrypt 方法时，我看不到任何编译器警告或错误(其中 IMyModel 实际上是一个接口(interface)而不是一个类):

_encryptor.Decrypt<IMyModel>(x.Patient)

为什么？

此代码是 nestandard20 项目的一部分。

Answer 1

您误解了类 constraint ，它将提供的类型参数强制为引用类型:

The type argument must be a reference type. This constraint applies also to any class, interface, delegate, or array type.