Problems creating a Foreign-Key relationship on Entity Framework

Question

i'm having trouble configuring a foreign key relationship in my Entity Framework fluent Api: Here is the head of the report: ``` public class Testata { public Testata() { Details = new List(); } public virtual int IDTEST { get; set; } public virtual string Value { get; set; } public virtual int IDDETAIL { get; set; } public virtual string IDTESTALT { get; set; } public virtual byte[] BLOB { get; set; } public virtual IList Details { get; set; } } ``` This is the report's detail ``` public class Dettaglio { public virtual int IDDETAIL { get; set; } public virtual int IDTEST { get; set; } public virtual string DSDETAIL { get; set; } public virtual Testata TEST_TABLE { get; set; } } ``` And this is my fluent API definition of both. Head of the report: ``` public TEST_TABLEMap() { // Primary Key this.HasKey(t => t.IDTEST) .Property(t => t.IDTEST) .IsRequired() .HasColumnType("Int") .HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity) .HasColumnName("IDTEST")…

Accepted Answer

There is a conflict between your foreign key property in class `Dettaglio`...

```
public virtual int IDTEST { get; set; }
```

...which has a non-nullable type (`int`) and therefore cannot be optional and your mapping...

```
this.HasOptional(t => t.TEST_TABLE) //...
```

...where you want the relationship to be optional.

If you indeed want an optional relationship use a nullable FK property:

```
public virtual int? IDTEST { get; set; }
```

Otherwise you must use `HasRequired` for a required relationship with a non-nullable FK property.

Problems creating a Foreign-Key relationship on Entity Framework

Solution

Problem