DataObjectFieldAttribute Class
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DataObjectFieldAttribute Class

 

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

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

System.Object
  System.Attribute
    System.ComponentModel.DataObjectFieldAttribute

[AttributeUsageAttribute(AttributeTargets.Property)]
public sealed class DataObjectFieldAttribute : Attribute

NameDescription
System_CAPS_pubmethodDataObjectFieldAttribute(Boolean)

Initializes a new instance of the DataObjectFieldAttribute class and indicates whether the field is the primary key for the data row.

System_CAPS_pubmethodDataObjectFieldAttribute(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.

System_CAPS_pubmethodDataObjectFieldAttribute(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.

System_CAPS_pubmethodDataObjectFieldAttribute(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.

NameDescription
System_CAPS_pubpropertyIsIdentity

Gets a value indicating whether a property represents an identity field in the underlying data.

System_CAPS_pubpropertyIsNullable

Gets a value indicating whether a property represents a field that can be null in the underlying data store.

System_CAPS_pubpropertyLength

Gets the length of the property in bytes.

System_CAPS_pubpropertyPrimaryKey

Gets a value indicating whether a property is in the primary key in the underlying data.

System_CAPS_pubpropertyTypeId

When implemented in a derived class, gets a unique identifier for this Attribute.(Inherited from Attribute.)

NameDescription
System_CAPS_pubmethodEquals(Object)

Returns a value indicating whether this instance is equal to a specified object.(Overrides Attribute.Equals(Object).)

System_CAPS_pubmethodGetHashCode()

Returns the hash code for this instance.(Overrides Attribute.GetHashCode().)

System_CAPS_pubmethodGetType()

Gets the Type of the current instance.(Inherited from Object.)

System_CAPS_pubmethodIsDefaultAttribute()

When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class.(Inherited from Attribute.)

System_CAPS_pubmethodMatch(Object)

When overridden in a derived class, returns a value that indicates whether this instance equals a specified object.(Inherited from Attribute.)

System_CAPS_pubmethodToString()

Returns a string that represents the current object.(Inherited from Object.)

NameDescription
System_CAPS_pubinterfaceSystem_CAPS_privmethod_Attribute.GetIDsOfNames(Guid, IntPtr, UInt32, UInt32, IntPtr)

Maps a set of names to a corresponding set of dispatch identifiers.(Inherited from Attribute.)

System_CAPS_pubinterfaceSystem_CAPS_privmethod_Attribute.GetTypeInfo(UInt32, UInt32, IntPtr)

Retrieves the type information for an object, which can be used to get the type information for an interface.(Inherited from Attribute.)

System_CAPS_pubinterfaceSystem_CAPS_privmethod_Attribute.GetTypeInfoCount(UInt32)

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

System_CAPS_pubinterfaceSystem_CAPS_privmethod_Attribute.Invoke(UInt32, Guid, UInt32, Int16, IntPtr, IntPtr, IntPtr, IntPtr)

Provides access to properties and methods exposed by an object.(Inherited from Attribute.)

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 NorthwindEmployee() { }

  private int _employeeID;
  [DataObjectFieldAttribute(true, true, false)]
  public int EmployeeID
  {
    get { return _employeeID; }
    set { _employeeID = value; }
  }

  private string _firstName = String.Empty;
  [DataObjectFieldAttribute(false, false, true)]
  public string FirstName
  {
    get { return _firstName; }
    set { _firstName = value; }
  }

  private string _lastName = String.Empty;
  [DataObjectFieldAttribute(false, false, true)]
  public string LastName
  {
    get { return _lastName; }
    set { _lastName = value; }
  }
}

.NET Framework
Available since 2.0

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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