[英]Entity Framework Core: FK with Different DataType than PK
运行时 :netcoreapp2.0
ASP.Net核心 :2.0.1
EF Core :2.0.1
Microsoft.EntityFrameworkCore.SqlServer :2.0.1
所以,我正在处理一个被许多服务使用的旧数据库,原始创建者将一个表的PK定义为short,将该表的FK定义为int。 我可以处理这个案子吗?
注意:此时更改列类型是不可行的。
考虑两个类:
public class Database {
public short DatabaseId { get; set; }
public Database { get; set; }
}
public class Client {
public int ClientId { get; set; }
public int DatabaseId { get; set; }
public Database Database { get; set; }
}
我的第一次尝试:
public int DatabaseId { get; set; }
[ForeignKey("DatabaseId")] public Database Database { get; set; }
投
System.InvalidOperationException: The relationship from 'Client.Database' to 'Database.Client' with foreign key properties {'DatabaseId' : int} cannot target the primary key {'DatabaseId' : short} because it is not compatible. Configure a principal key or a set of compatible foreign key properties for this relationship.
现在使用流畅的API:
modelBuilder.Entity<Client>(table => {
table.HasOne(p => p.Database)
.WithOne(i => i.Client)
.HasForeignKey<Client>(c => c.DatabaseId)
.HasPrincipalKey<Database>(d => d.DatabaseID);
});
尝试定义阴影属性失败
modelBuilder.Entity<Client>(table => {
table.Property<int>("DatabaseId");
table.HasOne(p => p.Database)
.WithOne(i => i.Client)
.HasForeignKey("DatabaseId")
.HasPrincipalKey<Database>(d => d.DatabaseId);
});
投
System.InvalidOperationException: You are configuring a relationship between 'Client' and 'Database' but have specified a foreign key on 'DatabaseId'. The foreign key must be defined on a type that is part of the relationship.
好的,这次没有影子属性:
modelBuilder.Entity<Client>(table => {
table.HasOne(p => p.Database)
.WithOne(i => i.Client)
.HasForeignKey<Client>(c => c.DatabaseId)
.HasPrincipalKey<Database>(d => d.SQLDatabaseID);
});
投
System.InvalidOperationException: The types of the properties specified for the foreign key {'DatabaseId'} on entity type 'Client' do not match the types of the properties in the principal key {'DatabaseID'} on entity type 'Database'.
所以,然后我尝试只更改实体类型,也许EF可以将int映射到int16。
public class Client {
public int ClientId { get; set; }
public short DatabaseId { get; set; } // <-- now a short
public Database Database { get; set; }
}
投
System.InvalidOperationException: An exception occurred while reading a database value for property 'Client.DatabaseId'. The expected type was 'System.Int16' but the actual value was of type 'System.Int32'. ---> System.InvalidCastException: Unable to cast object of type 'System.Int32' to type 'System.Int16'.
我开始觉得这是不可能的。
在EF Core 2.1中,您可以使用值转换,即
entityBuilder.Property(c => c.Id).HasConversion<string>();
其中通用字符串是数据库类型,目标是模型类型。 您可以在https://docs.microsoft.com/es-es/ef/core/modeling/value-conversions上进一步阅读
您可以使用以下代码来绕过实体框架生成的错误来定义外键
[Column(TypeName = "int")]
public short DatabaseId { get; set; }
但是一旦你运行迁移,你将收到此错误,这是由sql server生成的。
列'Databases.DatabaseId'与外键'FK_Clients_Databases_DatabaseId'中引用列'Clients.DatabaseId'的数据类型不同。
这很有道理。 您尝试实现的内容在物理上是不可能的,因为SQL Server要求外键是相同的类型,否则您无法构建外键关系。
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