为什么EF核心无效的实体原因是“预期类型是system.String＆＃x27;但是实际价值是无效的？”

发布于 2025-01-23 23:34:30 字数 1241 浏览 2 评论 0原文

之间有多一关系

modelBuilder.Entity<Party>()
  .HasMany(p => p.PartyMembers)
  .WithOne(p => p.Party);

使用实体框架6和.NET 6，我在party和statentity 有一个party：

[NotLogged] [JsonIgnore] public Party? Party { get; set; }

的确，我们可以看到party根据自动生成的迁移而配置为无效：

migrationBuilder.AlterColumn<string>(
                name: "PartyId",
                table: "StatEntities",
                type: "varchar(36)",
                nullable: true,
                oldClrType: typeof(string),
                oldType: "varchar(36)")
                .Annotation("MySql:CharSet", "latin1")
                .OldAnnotation("MySql:CharSet", "latin1");

根据__ __ efmigrations history，迁移是成功应用。
数据库中存在null party>的值。

但是，当我尝试查询statentity具有null的值party> party 时，我会收到以下内容：

在读取属性'statentity.partyid'的数据库值时发生错误。预期的类型为“系统。弦”，但实际值为null。

请注意，我是不是尝试.include（statentity =＆gt; statentity.party）。似乎EF Core不允许为影子属性提供零值，即使它被称为此类属性。

原文

Using Entity Framework 6 and .NET 6, I have a many-to-one relationship between Party and StatEntity:

modelBuilder.Entity<Party>()
  .HasMany(p => p.PartyMembers)
  .WithOne(p => p.Party);

Where the StatEntity may not necessarily have a Party:

[NotLogged] [JsonIgnore] public Party? Party { get; set; }

Indeed, we can see that PartyId is configured as nullable based upon the auto generated migration:

migrationBuilder.AlterColumn<string>(
                name: "PartyId",
                table: "StatEntities",
                type: "varchar(36)",
                nullable: true,
                oldClrType: typeof(string),
                oldType: "varchar(36)")
                .Annotation("MySql:CharSet", "latin1")
                .OldAnnotation("MySql:CharSet", "latin1");

According to __EFMigrationsHistory, the migration was successfully applied.
There exist null values for PartyId in the database.

However, when I try to query a StatEntity that has a null value for PartyId, I receive the following:

An error occurred while reading a database value for property 'StatEntity.PartyId'. The expected type was 'System.String' but the actual value was null.

Note that I am not attempting to .Include(statEntity => statEntity.Party). It seems that EF Core is not allowing null values for the shadow property, even though it is declared as such.

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爱殇璃 2025-01-30 23:34:30

作为一个工作障碍，明确定义statentity上的影子属性似乎可以解决该问题：

    [NotLogged] [JsonIgnore] public string? PartyId { get; set; }

    [NotLogged] [JsonIgnore] public FurballParty? Party { get; set; }

奇怪的是，运行dotnet ef ef迁移添加blah创建一个空迁移，因此肯定数据库方面没有错。它似乎是EFCORE中的一个错误，它导致基础阴影属性无法正确定义为无效。

As a work-around, explicitly defining the shadow property on the StatEntity appears to fix the problem:

    [NotLogged] [JsonIgnore] public string? PartyId { get; set; }

    [NotLogged] [JsonIgnore] public FurballParty? Party { get; set; }

Curiously, running a dotnet ef migrations add blah creates an empty migration, so definitely nothing wrong with the database aspect. It appears to be a bug in EFCore that causes the underlying shadow property to not be correctly defined as nullable.

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