Query: We should throw when accessing non-nullable property over a null-value entity in the projection #20633

maumar · 2020-04-14T22:18:38Z

query:

ctx.Gears.Select(g => g.AssignedCity.Name.Length);

assuming assigned city can be null, we should throw "nullable object must have a value" (or ideally something more meaningful).

Currently we return default(int) - it might not be what user expected.
Casting result to nullable will yield correct result (and would get rid of the exception in the future)

ctx.Gears.Select(g => (int?)g.AssignedCity.Name.Length);

maumar · 2020-04-14T22:21:21Z

Note: in 2.1 we would throw in this case, which we changed in 3.1. We want to go back to 2.1 behavior.

ajcvickers · 2020-04-17T20:59:21Z

Notes from team discussion: we should do this alongside the other related change such that Sum queries still return correct values. Then I don't think this is a breaking change because it is only changing the result in places where it was previously wrong.

In 3.x when reading values from database, we started returning default value of expected type if the value was null in the database. That means if we needed to read int then database value was null then we got 0 back. Which is not correct as we should throw exception for the case. The fix here is, - All value read from databases are of nullable type as database can return null. - Since all the bindings with database are nullable now, - When doing member access we add null check and return nullable of return type - When doing method call we add null check for instance. All parameters we convert to original types. - All other expressions, where they need to match the type to reconstruct the original tree, adds convert nodes. - For translation of Single/SingleOrDefault (and friends) - For scalar subquery - We add coalesce with default value for SingleOrDefault - We don't add coalesce for Single case and assume there will be non-null value coming out of database which we will try to assign. - For non-scalar subquery - We add default value in client side in shaper for SingleOrDefault - We throw exception Sequence contains no elements for Single case - Above rules are only when not returning entity type. When returning entity type, we don't have enough information to differentiate the case. Also above behavior is just side-effect of assigning values to properties which cannot take null values. - When doing DefaultIfEmpty over a non-reference type, navigation expansion will add client side coalesce so that we can move Selector after DefaultIfEmpty Resolves #20633 Resolves #20959 Resolves #21002

In 3.x when reading values from database, we started returning default value of expected type if the value was null in the database. That means if we needed to read int then database value was null then we got 0 back. Which is not correct as we should throw exception for the case. The fix here is, - All value read from databases are of nullable type as database can return null. - Since all the bindings with database are nullable now, - When doing member access we add null check for value types and return nullable of return type - When doing method call we add null check for instance. All parameters we convert to original types. - All other expressions, where they need to match the type to reconstruct the original tree, adds convert nodes. - For translation of Single/SingleOrDefault (and friends) - For scalar subquery - We add coalesce with default value for SingleOrDefault - We don't add coalesce for Single case and assume there will be non-null value coming out of database which we will try to assign. - For non-scalar subquery - We add default value in client side in shaper for SingleOrDefault - We throw exception Sequence contains no elements for Single case - Above rules are only when not returning entity type. When returning entity type, we don't have enough information to differentiate the case. Also above behavior is just side-effect of assigning values to properties which cannot take null values. - When doing DefaultIfEmpty over a non-reference type, navigation expansion will add client side coalesce so that we can move Selector after DefaultIfEmpty Resolves #20633 Resolves #20959 Resolves #21002

If the summary does not exist, SummaryId can be null. The bug has exist since the first day, but it had not been revealed until the fix in entity framework 5. see dotnet/efcore#22517 and dotnet/efcore#20633

maumar added customer-reported breaking-change type-bug and removed customer-reported labels Apr 14, 2020

maumar changed the title ~~We should throw when accessing non-nullable property over a null-value entity in the projection~~ Query: We should throw when accessing non-nullable property over a null-value entity in the projection Apr 14, 2020

smitpatel self-assigned this Apr 14, 2020

smitpatel mentioned this issue Apr 15, 2020

Query: SqlExpression.Type is non-nullable even when it could be null #20637

Closed

ajcvickers added the area-query label Apr 17, 2020

ajcvickers added this to the 5.0.0 milestone Apr 17, 2020

ajcvickers removed the breaking-change label Apr 17, 2020

smitpatel mentioned this issue May 16, 2020

DateTimeOffset to DateTime Null Conversion #20959

Closed

maumar mentioned this issue May 20, 2020

Subquery materializes zero in place of null #21002

Closed

This was referenced Jun 10, 2020

Fix to #12657 - Query: logic protecting SUM from returning null doesn't work for complex scenarios #21203

Merged

Fix NumberToBytesConverter for empty arrays #21269

Closed

bdebaere mentioned this issue Jun 16, 2020

NumberToBytesConverter on ulong RowVersion property fails with .Include query #12518

Closed

smitpatel mentioned this issue Jul 17, 2020

Query: Don't read default value from databases #21668

Merged

smitpatel added the closed-fixed The issue has been fixed and is/will be included in the release indicated by the issue milestone. label Jul 18, 2020

smitpatel modified the milestones: 5.0.0, 5.0.0-preview8 Jul 18, 2020

ajcvickers closed this as completed in 3ebfde7 Jul 18, 2020

smitpatel mentioned this issue Sep 1, 2020

Nullable exception after updating to Preview-8 (Nullable object must have a value) #22348

Closed

smitpatel mentioned this issue Sep 14, 2020

Result of left joining a nullable nominal type should be null (i.e. no instance) and not an instance with all null property values #22517

Open

ajcvickers modified the milestones: 5.0.0-preview8, 5.0.0 Nov 7, 2020

smitpatel mentioned this issue Nov 18, 2020

Query: Aggregate result operators should return appropriate type from server side #16988

Closed

smitpatel mentioned this issue Jul 20, 2021

Why Does Upgrading to .Net 5.0 cause error: System.InvalidOperationException: 'Nullable object must have a value.' #25284

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Query: We should throw when accessing non-nullable property over a null-value entity in the projection #20633

Query: We should throw when accessing non-nullable property over a null-value entity in the projection #20633

maumar commented Apr 14, 2020

maumar commented Apr 14, 2020 •

edited

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ajcvickers commented Apr 17, 2020

Query: We should throw when accessing non-nullable property over a null-value entity in the projection #20633

Query: We should throw when accessing non-nullable property over a null-value entity in the projection #20633

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maumar commented Apr 14, 2020

maumar commented Apr 14, 2020 • edited Loading

ajcvickers commented Apr 17, 2020

maumar commented Apr 14, 2020 •

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