Contravariance in inheritance
Is there a way to make the return type contravariant in inherited types? See sample code below. I need this for Entity Framework.
public class InvoiceDetail
{
public virtual ICollection<Invoice> Invoices { get; set; }
}
public class SalesInvoiceDetail : InvoiceDetail
{
//This is not allowed by the compiler, but what we are trying to achieve is that the return type
//should be ICollection<SalesInvoice> instead of ICollection<Invoice>
public override ICollection<SalesInvoice> Invoices { get; set; }
}
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1 answer
You can apply generics with appropriate constraints
public abstract class InvoiceDetailBase<T> where T : Invoice
{
public virtual ICollection<T> Invoices { get; set; }
}
public class InvoiceDetail : InvoiceDetailBase<Invoice>
{
}
public class SalesInvoiceDetail : InvoiceDetailBase<SalesInvoice>
{
}
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