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Showing content from https://docs.microsoft.com/en-us/dotnet/api/system.data.linq.mapping.associationattribute below:

AssociationAttribute Class (System.Data.Linq.Mapping) | Microsoft Learn

Designates a property to represent a database association, such as a foreign key relationship.

public ref class AssociationAttribute sealed : System::Data::Linq::Mapping::DataAttribute

[System.AttributeUsage(System.AttributeTargets.Field | System.AttributeTargets.Property, AllowMultiple=false)]
public sealed class AssociationAttribute : System.Data.Linq.Mapping.DataAttribute

[<System.AttributeUsage(System.AttributeTargets.Field | System.AttributeTargets.Property, AllowMultiple=false)>]
type AssociationAttribute = class
    inherit DataAttribute

Public NotInheritable Class AssociationAttribute
Inherits DataAttribute

Inheritance

Attributes

private EntityRef<Customer> _Customer;
// ...
[Association(Name="FK_Orders_Customers", Storage="_Customer", ThisKey="CustomerID", IsForeignKey=true)]
public Customer Customer
{
    get
    {
        return this._Customer.Entity;
    }
    set
    {
        Customer previousValue = this._Customer.Entity;
        if (((previousValue != value)
                    || (!this._Customer.HasLoadedOrAssignedValue )))
        {
            this.SendPropertyChanging();
            if ((previousValue != null))
            {
                this._Customer.Entity = null;
                previousValue.Orders.Remove(this);
            }
            this._Customer.Entity = value;
            if ((value != null))
            {
                value.Orders.Add(this);
                this._CustomerID = value.CustomerID;
            }
            else
            {
                this._CustomerID = default(string);
            }
            this.SendPropertyChanged("Customer");
        }
    }
}

Private _Customer As EntityRef(Of Customer)
<Association(Name:="FK_Orders_Customers", Storage:="_Customer", ThisKey:="CustomerID", IsForeignKey:=True)>
Public Property Customer() As Customer
    Get
        Return Me._Customer.Entity
    End Get
    Set(ByVal value As Customer)
        Dim previousValue As Customer = Me._Customer.Entity
        If (((previousValue Is value) _
           = False) _
           OrElse (Me._Customer.HasLoadedOrAssignedValue = False)) Then
            Me.SendPropertyChanging()
            If ((previousValue Is Nothing) _
               = False) Then
                Me._Customer.Entity = Nothing
                previousValue.Orders.Remove(Me)
            End If
            Me._Customer.Entity = value
            If ((value Is Nothing) _
               = False) Then
                value.Orders.Add(Me)
                Me._CustomerID = value.CustomerID
            Else
                Me._CustomerID = CType(Nothing, String)
            End If
            Me.SendPropertyChanged("Customer")
        End If
    End Set
End Property

Use this attribute to represent an association in a database, such as the relationship between a foreign key and a primary key.

In the following example, the Order class includes an AssociationAttribute attribute to associate Orders with Customers.

When placed on a 1:1 association whose foreign key members are all non-nullable, deletes the object when the association is set to null.

Gets or sets delete behavior for an association.

Gets or sets the member as the foreign key in an association representing a database relationship.

Gets or sets the indication of a uniqueness constraint on the foreign key.

Gets or sets the name of a column.

Gets or sets one or more members of the target entity class as key values on the other side of the association.

Gets or sets a private storage field to hold the value from a column.

Gets or sets members of this entity class to represent the key values on this side of the association.

When implemented in a derived class, gets a unique identifier for this Attribute.

Maps a set of names to a corresponding set of dispatch identifiers.

Retrieves the type information for an object, which can be used to get the type information for an interface.

Retrieves the number of type information interfaces that an object provides (either 0 or 1).

Provides access to properties and methods exposed by an object.

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