Shadow properties

[lars-lindstrom]

Shadow properties

[r2baka]

do I have to use DbContext (which I try to avoid)

I do know the answer to that is no.

You can do something like q.Where(p => (p.Firstname + ' ' + p.Lastname).Contains(searchname));

That doesn't solve problems like the duplication of code to calculate the fullname, but it does help you avoid DbContext.

For the general case like this, where I want to avoid DbContext, but still have deeper flexibility on my queries, I just made a ListBySQL method on the repository, which comes in very handy for difficult use cases for the Query. but you kinda have to like SQL.

public class EfRepository<T> : IAsyncRepository<T> where T : BaseEntity, IAggregateRoot
{

...
public async Task<IReadOnlyList> ListBySQLAsync(string sql, object[] parameters)
{

            return await _dbContext.Set<T>().FromSqlRaw(sql, parameters).ToListAsync();

    }

Alternatively, you could also create a calculated field on the data set where a column FullName = Firstname + ' ' + Lastname
https://learn.microsoft.com/en-us/sql/relational-databases/tables/specify-computed-columns-in-a-table?view=sql-server-ver16

[fiseni]

Hi @lars-lindstrom

You can have the following specification

public class CustomerSpec : Specification<Customer>
{
    public CustomerSpec(string someValue)
    {
        Query.Where(x => EF.Property<string>(x, "Fullname").Contains(someValue));
    }
}

Also, you have to configure the shadow properties in your EF Core configuration. It would be something as follows:

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<Customer>().Property<string>("Fullname");
}

You don't depend on DbContext in the specification, but still, you depend on the static EF class which is defined in Microsoft.EntityFrameworkCore. So, you'll depend on EF Core, if that's what you mean.
If you're asking for a mechanism to abstract that dependency, then we don't plan to implement that, unfortunately. It can be implemented through reflection and dynamically build the expression. But, we're trying to avoid reflection as much as possible, especially now that .NET is serious about AOT. Also, there is no good way to generalize the usage. You're thinking only in terms of Contains, but the expression inside the Where can be anything (e.g. Any, Equals, etc.). What would the new API look like?

Specifications are intended to operate against a defined domain model. The shadow properties, by definition, are not part of it. You might reconsider the need for a shadow property. What's exactly your case? I assume you have such a column in the database right? Then, why not add the property to the model?

[fiseni]

Hey @lars-lindstrom,

Do you have any further questions or comments? Should we close this issue?

[fiseni]

Closing the issue due to inactivity. If you have further questions or comments, please feel free to reply.