How do you create a foreign key in the code first approach?
To create a foreign key, you must use the ForeignKey attribute by specifying the property name as a parameter. You must also specify the name of the table that will participate in the relationship. I mean, define the foreign key table.
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How is a one-to-one relationship represented in a database?
Primary Key as Foreign Key One way to implement a one-to-one relationship in a database is to use the same primary key in both tables. Rows with the same primary key value are related. In this example, France is a country with id 1 and its capital city is in the capital table under id 1.
Do you need the navigation property first for the EF code?
With EF Code First Fluent API it is impossible. You always need at least one navigation property to create a foreign key constraint in the database. If you’re using Code First Migrations, you have the option to add a new code-based migration in the Package Manager Console ( add-migration SomeNewSchemaName ).
How are navigation properties defined in the Entity Framework?
The first part of the expression defines the navigation property on the current entity, the second part of the expression defines the reverse navigation property. The properties of the navigation properties can be Optional (ie 0..1 ax), Required (ie 1 ax), or Many (ie ** ax*). So let’s take a look at some examples:
When to use foreign key in navigation property?
The foreign key attribute is used on a navigation property. So at this stage, it will give an error, because here we have specified a foreign key. So EF will not create a default foreign key by [PropertyName]_[PropertyIdName]. Therefore, EF tries to find the foreign key, specified by the name “FkClientId”.
How to use parentid as foreign key in EF?
Alternatively, without migrations, you can just run a pure SQL command using where context is an instance of your derived context class and sql is just the previous SQL command as a string. Note that with all of this, EF has no idea that ParentId is a foreign key that describes a relationship. EF will consider it just an ordinary scalar property.