Ef core value comparer Jan 12, 2023 · For small, immutable value types such as int, EF Core's default logic works well: the value is copied as-is when snapshotted, and compared with the type's built-in equality comparison. Doing this on EF Core 3, I get the following warning: « The property '{property}' on entity type '{entityType}' is a collection or enumeration type with a value converter but with no value comparer. Sep 13, 2022 · Instead, create types that inherit from ValueConverter and ValueComparer and use 'HasConversion=<ConverterType, ComparerType=>()' or 'HasConversion(Type converterType, Type comparerType)' to configure the value converter and comparer. 简单结构的映射也很简单，不需要特殊的比较器或快照截取。 public readonly struct ImmutableStruct { public ImmutableStruct(int value) { Value = value; } public int Value { get; } } Seems someone has been struggling with that and found solution. 3. 1 The definition of the entity is as follows: Remarque. 测试 Jul 5, 2023 · , on the other hand, performs case-sensitive string comparisons by default. Snapshotting is the process of creating a copy of the value into a snapshot so it can later be compared to determine if it has changed. Cela est dû au fait qu’EF Core insère ces expressions dans une arborescence d’expressions beaucoup plus complexe qui est ensuite compilée dans un délégué du modélisateur d’entité. For simple types/value types (int, string, etc), this is straightforward. For example: var valueComparer = new ValueComparer < ICollection < MySmartEnum > > ( ( c1 , c2 ) => c1 . . 从 1. First, how are equality comparisons made? Especially with 8. 11 Database provider: Microsoft. Dec 7, 2020 · Why is it useful being able to compare dictionary values by using a specified equality semantic? I totally understand the necessity of being able to compare dictionary keys by using a specified equality semantic, but I can't get the point for value comparison. Oct 21, 2022 · EF Core version: 7. 0. SqlServer Target framework: . See: Store a Dictionary as a JSON string using EF Core 2. This means that EF Core will snapshot (copy) your property contents when the entity is loaded from the database, and when SaveChanges is called, that snapshot will be compared against the updated version to see if anything changed. This is an internal API that supports the Entity Framework Core infrastructure and not subject to the same compatibility standards as public APIs. In the below example we are adding our custum value comparer. 新增功能; 重大更改; EF Core 2. 0; 从以前的版本升级. EntityFrameworkCore. 连接字符串; Logging; 连接复原; 正在测试. 2. 0 Operating system: Windows 2011 IDE: Visual Studio 2022 17. Specifies custom value snapshotting and comparison for CLR types that cannot be compared with Equals(Object, Object) and/or need a deep copy when taking a snapshot. The property 'Roles' on entity type 'EmployeeSummary' is a collection or enumeration type with a value converter but with no value comparer. Mar 16, 2025 · Where the EF Core default behavior is not suitable, you may provide a value comparer, which contains logic for snapshotting, comparing and calculating a hash code. NET Core 教程 >> 基础知识. Oct 25, 2023 · I have a few questions regarding the equality comparisons of complex value objects mapped with OwnsOne()/OwnsMany() combined with ToJson(). 1; EF Core 2. 0 RC2 升级到 RTM; 从 1. A value comparer for keys can be used to force EF Core into case-insensitive string comparisons like in the database. 1; EF Core 1. When implementing your own value comparer, it's important to consider whether deep or shallow comparison (and snapshotting) logic is appropriate. Sep 13, 2023 · 因此，在这种情况下，EF Core 的默认行为本身就是正常的。 简单的不可变结构. 0's support for non-primitive collections, it seems essential that collections are compared structurally. 22472. See EF Core value comparers for more information and examples. Creates a new ValueComparer with the given comparison and snapshotting expressions. Set a value comparer to ensure the collection/enumeration elements are compared correctly. 0; 入门. EF Core 教程; 安装 EF Core; ASP. This means that a foreign key value like "DotNet" will match the primary key value "dotnet" on SQL Server, but will not match it in EF Core. Jan 24, 2020 · The basic idea here is EF Core will track changes to the entities by taking snapshots. Oct 16, 2020 · If you want EF Core to automatically detect changes to the contents of your property, you're going to have to set up a value comparer on it. 0-rc. 2; EF Core 2. Oct 5, 2023 · By default, EF Core uses the default equality comparison defined by types (e. 1 When upgrading from EFCore 6 to the release candidat EF Core 3. Jan 12, 2023 · For small, immutable value types such as int, EF Core's default logic works well: the value is copied as-is when snapshotted, and compared with the type's built-in equality comparison. For some types, such as collections, this needs to be a deep copy of the collection rather than just a shallow copy of the reference. It will compare these snapshots and determine whether or not entities has changed. Les convertisseurs et comparateurs de valeurs sont construits à l’aide d’expressions plutôt que de délégués simples. 0 RC1 升级到 RC2; 从 1. x 升级到 2. the Equals method); for snapshotting, value types are copied to produce the snapshot, while for reference types no copying occurs, and the same instance is used as the snapshot. For example, arrays of primitive types will require both if mutation is to be detected. g. NET 6. 0; EF Core 1. Jan 5, 2020 · The property 'AvailableProductBrands' on entity type 'Review' is a collection or enumeration type with a value converter but with no value comparer. Aug 28, 2019 · The fix for this is to tell EF how to snapshot and compare these collections. vyyqhlnerqdtpomrrckhfqrpdzfyjzzcktulzroslxfwgjveysaobyhpyukmpijp