ColumnAttribute.Expression Property  
Definition
Important
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Gets or sets whether a column is a computed column in a database.
public:
 property System::String ^ Expression { System::String ^ get(); void set(System::String ^ value); };public string Expression { get; set; }member this.Expression : string with get, setPublic Property Expression As StringProperty Value
Default = empty.
Examples
[Column(Storage="_UnitPrice", DbType="Money",Expression="UnitPrice + 1.00")]
public System.Nullable<decimal> UnitPrice
{
    get
    {
        return this._UnitPrice;
    }
    set
    {
        if ((this._UnitPrice != value))
        {
            this.OnUnitPriceChanging(value);
            this.SendPropertyChanging();
            this._UnitPrice = value;
            this.SendPropertyChanged("UnitPrice");
            this.OnUnitPriceChanged();
        }
    }
}
   <Column(Storage:="_UnitPrice", DbType:="Money NOT NULL", Expression:="UnitPrice + 1.00")> _
Public Property UnitPrice() As Decimal
       Get
           Return Me._UnitPrice
       End Get
       Set(ByVal value As Decimal)
           If ((Me._UnitPrice = Value) _
              = False) Then
               Me.OnUnitPriceChanging(Value)
               Me.SendPropertyChanging()
               Me._UnitPrice = Value
               Me.SendPropertyChanged("UnitPrice")
               Me.OnUnitPriceChanged()
           End If
       End Set
   End Property
Remarks
Use this property when you use CreateDatabase to define a column as containing computed values.
For example, if you want to create a column defined in SQL as InventoryVal AS UnitPrice * UnitsInStock, use the following expression string: "UnitPrice * UnitsInStock".
Note
LINQ to SQL does not support computed columns as primary keys.