Entity Frameworks SqlRaw
has a small, sometimes annoying limitation:
The SQL query must return data for all properties of the entity type.
Sometimes that isn't desirable, so let's overcome that super easy.
The limitation
Imagine you have an object like this:
public sealed record MyEntity
{
public double? PropA { get; init; }
public double? PropB { get; init; }
}
Basically, we express that either PropA
or PropB
are optional and therefore if not present in the result set, should be null
. But SqlRaw
expects all properties in an entity present in the SELECT
clause.
So:
dbContext
.Database
.SqlQuery<MyEntity>($"SELECT PropA FROM MyTable")
.ToListAsync(token);
Will fail with an exception that EF can't map the query to the type as there is PropB
missing.
To simply overcome this, return PropB
explicitly as NULL
:
dbContext
.Database
.SqlQuery<MyEntity>($"SELECT PropA, NULL AS PropB FROM MyTable")
.ToListAsync(token);
Tada, EF is happy again. Of course that is an oversimplified example, but you get the idea.