IMergeable.UpdateWhenMatched: How can I provide custom setters for SOME of the fields, and use default for others

[bt-88]

As is

Currently, for merge operations, you provide two overloads:

• UpdateWhenMatched(): Updates all fields that are in both source and target
• UpdateWhenMatched(Expression<Func<TTarget,TSource,TTarget>> setter): Updates the fields as specified in the user defined setter

To be

What I would like to have is a combination of both. That is, it updates all fields that are in both source and target AND applies the custom 'overrides' for some of the fields.

Use case

Use case. Have user defined setters for the UpdatedAt and CreatedAt fields in my base entity, but use the default update setters for all other fields.

.UpdateWhenMatched((target,source)=> new TTarget
            {
                CreatedAt = target.FusionCreatedAt,
                UpdatedAt = DateTime.UtcNow,
                // Use defaults for all other fields without the need to specify them explicitly
            });

The same applies to .InsertWhenNotMatched. Here I would like to do:

.InsertWhenNotMatched( _ => new TTarget { CreatedAt = DateTime.UtcNow, // Use defaults for all other fields without the need to specify them explicitly })

[bt-88]

Anyone? If someone can guide me in the right direction I'm willing to draft a PR for this.

[sdanyliv]

Sorry for delay, it needs API design, not simple thing right now. I can help you to write such method without changing linq2db code.

[bt-88]

Sorry for delay, it needs API design, not simple thing right now. I can help you to write such method without changing linq2db code.

Thank you, that would be awesome. Please show me how when you have the time.

[sdanyliv]

I assume it should work only if TSource and TTarget are the same?

[bt-88]

I assume it should work only if TSource and TTarget are the same?

Yes, correct.

[sdanyliv]

Duplicate https://github.com/linq2db/linq2db/issues/4357

[sdanyliv]

Added answer in linq2db repository.