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DataObjectFieldAttribute Class

Provides metadata for a property representing a data field. This class cannot be inherited.

System.Object
  System.Attribute
    System.ComponentModel.DataObjectFieldAttribute

Namespace:  System.ComponentModel
Assembly:  System (in System.dll)

'Declaration
<AttributeUsageAttribute(AttributeTargets.Property)> _
Public NotInheritable Class DataObjectFieldAttribute _
	Inherits Attribute

The DataObjectFieldAttribute type exposes the following members.

  NameDescription
Public methodDataObjectFieldAttribute(Boolean)Initializes a new instance of the DataObjectFieldAttribute class and indicates whether the field is the primary key for the data row.
Public methodDataObjectFieldAttribute(Boolean, Boolean)Initializes a new instance of the DataObjectFieldAttribute class and indicates whether the field is the primary key for the data row, and whether the field is a database identity field.
Public methodDataObjectFieldAttribute(Boolean, Boolean, Boolean)Initializes a new instance of the DataObjectFieldAttribute class and indicates whether the field is the primary key for the data row, whether the field is a database identity field, and whether the field can be null.
Public methodDataObjectFieldAttribute(Boolean, Boolean, Boolean, Int32)Initializes a new instance of the DataObjectFieldAttribute class and indicates whether the field is the primary key for the data row, whether it is a database identity field, and whether it can be null and sets the length of the field.
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  NameDescription
Public propertyIsIdentityGets a value indicating whether a property represents an identity field in the underlying data.
Public propertyIsNullableGets a value indicating whether a property represents a field that can be null in the underlying data store.
Public propertyLengthGets the length of the property in bytes.
Public propertyPrimaryKeyGets a value indicating whether a property is in the primary key in the underlying data.
Public propertyTypeIdWhen implemented in a derived class, gets a unique identifier for this Attribute. (Inherited from Attribute.)
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  NameDescription
Public methodEqualsReturns a value indicating whether this instance is equal to a specified object. (Overrides Attribute.Equals(Object).)
Protected methodFinalizeAllows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public methodGetHashCodeReturns the hash code for this instance. (Overrides Attribute.GetHashCode.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodIsDefaultAttributeWhen overridden in a derived class, indicates whether the value of this instance is the default value for the derived class. (Inherited from Attribute.)
Public methodMatchWhen overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute.)
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
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  NameDescription
Explicit interface implemetationPrivate method_Attribute.GetIDsOfNamesMaps a set of names to a corresponding set of dispatch identifiers. (Inherited from Attribute.)
Explicit interface implemetationPrivate method_Attribute.GetTypeInfoRetrieves the type information for an object, which can be used to get the type information for an interface. (Inherited from Attribute.)
Explicit interface implemetationPrivate method_Attribute.GetTypeInfoCountRetrieves the number of type information interfaces that an object provides (either 0 or 1). (Inherited from Attribute.)
Explicit interface implemetationPrivate method_Attribute.InvokeProvides access to properties and methods exposed by an object. (Inherited from Attribute.)
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Use the DataObjectFieldAttribute attribute to provide information about the schema of the underlying data. Design-time classes such as the ObjectDataSourceDesigner class use the DataObjectAttribute attribute to set properties at design-time based on the exposed schema.

You apply the DataObjectFieldAttribute attribute to members of the data item objects that are returned by the Select method of an object marked with the DataObjectAttribute attribute. In the following example, the NorthwindData class is marked with the DataObjectAttribute attribute, and returns an IEnumerable object containing NorthwindEmployee objects from the GetAllEmployees method. Fields in the NorthwindEmployee class are marked with the DataObjectFieldAttribute attribute to indicate they represent data fields in the underlying data source.

For more information about using attributes, see Extending Metadata Using Attributes.

The following code example demonstrates how you can apply the DataObjectFieldAttribute to a publicly exposed property to identify metadata associated with the property. In this example the NorthwindEmployee type exposes three data properties: EmployeeID, FirstName, and LastName. The DataObjectFieldAttribute attribute is applied to all three properties; however, only the EmployeeID property attribute indicates it is the primary key for the data row.


Public Class NorthwindEmployee

  Public Sub New()
  End Sub 'New 

  Private _employeeID As Integer
  <DataObjectFieldAttribute(True, True, False)> _
  Public Property EmployeeID() As Integer
    Get
      Return _employeeID
    End Get
    Set(ByVal value As Integer)
      _employeeID = value
    End Set
  End Property

  Private _firstName As String = String.Empty
  <DataObjectFieldAttribute(False, False, False)> _
  Public Property FirstName() As String
    Get
      Return _firstName
    End Get
    Set(ByVal value As String)
      _firstName = value
    End Set
  End Property

  Private _lastName As String = String.Empty
  <DataObjectFieldAttribute(False, False, False)> _
  Public Property LastName() As String
    Get
      Return _lastName
    End Get
    Set(ByVal value As String)
      _lastName = value
    End Set
  End Property

End Class 'NorthwindEmployee


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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