LC028: Deep ThenInclude Chain

What it flags

Flags EF Core ThenInclude(...) chains once they exceed the configured maximum depth. By default, LC028 allows three consecutive ThenInclude(...) calls after an Include(...) and reports the fourth call as the point where the query should be reviewed.

Why it matters

Very deep eager-loading chains often signal over-fetching, brittle query shapes, and poor separation between read models and entity graphs. They can also generate wide SQL with many joins and duplicated row data.

LC028 is intentionally heuristic: a deep Include graph can be valid for small reference data, aggregate snapshots, or carefully profiled queries. The diagnostic asks for a manual review rather than prescribing a universal rewrite.

Safe and intentional shapes

LC028 does not report the first three ThenInclude(...) calls by default. If a project has a known, reviewed deep graph, either suppress the specific diagnostic with a justification or raise the threshold for that scope:

[*.cs]
dotnet_code_quality.LC028.max_depth = 4

The threshold must be a positive integer. Invalid values keep the default of 3.

Typical fix

Prefer focused projections, split queries, or targeted follow-up loads for the specific data the caller actually consumes. There is no automatic fix because removing eager-loading depth requires a domain-specific decision about result shape, tracking behavior, and query ownership.

Samples

See samples/LinqContraband.Sample/Samples/LC028_DeepThenInclude/ for a focused example.

The crime

var query = db.Customers
    .Include(c => c.Orders)
        .ThenInclude(o => o.LineItems)
            .ThenInclude(li => li.Product)
                .ThenInclude(p => p.Supplier);

A better shape

var query = db.Customers
    .Select(c => new
    {
        c.Id,
        Orders = c.Orders.Select(o => new
        {
            o.Id,
            Items = o.LineItems.Select(li => new { li.Id, li.Product.Name })
        })
    });