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Facets (CSDL)

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Facets in conceptual schema definition language (CSDL) represent constraints on properties of entity types and complex types. Facets appear as XML attributes on the following CSDL elements:

The following table describes the facets that are supported in CSDL. All facets are optional. Some facets listed below are used by the Entity Framework when generating a database from a conceptual model. For more information, see Generate Database Wizard.

Note

For information about data types in a conceptual model, see Conceptual Model Types (CSDL).

Facet Description Applies to Used for the database generation Used by the runtime

Collation

Specifies the collating sequence (or sorting sequence) to be used when

performing comparison and ordering operations on values of the property.

Edm.String

Yes

No

ConcurrencyMode

Indicates that the value of the property should be used for

optimistic concurrency checks.

All EDMSimpleType properties

No

Yes

Default

Specifies the default value of the property if

no value is supplied upon instantiation.

All EDMSimpleType properties

Yes

Yes

FixedLength

Specifies whether the length of the property value can vary.

Edm.Binary, Edm.String

Yes

No

MaxLength

Specifies the maximum length of the property value.

Edm.Binary, Edm.String

Yes

No

Nullable

Specifies whether the property can have a null value.

All EDMSimpleType properties

Yes

Yes

Precision

For properties of type Decimal, specifies the number of digits a property value can have.

For properties of type Time, DateTime, and DateTimeOffset,

specifies the number of digits for the fractional part of seconds of the property value.

Edm.DateTime, Edm.DateTimeOffset,

Edm.Decimal, and Edm.Time.

Yes

No

Scale

Specifies the number of digits to the right of the decimal point for the property value.

Edm.Decimal

Yes

No

Unicode

Indicates whether the property value is stored as Unicode.

Edm.String

Yes

Yes

Note   When generating a database from a conceptual model, the Generate Database Wizard will recognize the value of the StoreGeneratedPattern attribute on a Property element if it is in the following namespace: https://schemas.microsoft.com/ado/2009/02/edm/annotation. The supported values for the attribute are Identity and Computed. A value of Identity will produce a database column with an identity value that is generated in the database. A value of Computed will produce a column with a value that is computed in the database.

Example

The following example shows facets applied to the properties of an entity type:

<EntityType Name="Product">
  <Key>
    <PropertyRef Name="ProductId" />
  </Key>
  <Property Type="Int32" 
            Name="ProductId" Nullable="false" 
            a:StoreGeneratedPattern="Identity" 
   xmlns:a="https://schemas.microsoft.com/ado/2009/02/edm/annotation" />
  <Property Type="String" 
            Name="ProductName" 
            Nullable="false" 
            MaxLength="50" />
  <Property Type="String" 
            Name="Location" 
            Nullable="true" 
            MaxLength="25" />
</EntityType>

For more information, see Property Element (CSDL).

See Also

Reference

System.Data.Metadata.Edm.Facet

Concepts

CSDL Specification

Other Resources

facet (Entity Data Model)
CSDL, SSDL, and MSL Specifications