Tài liệu The ForeignKeyConstraint Class pdf

This ensures that each DataRow in your child DataTable has a matching DataRow in your parent DataTable.. Table 12.2: ForeignKeyConstraint PROPERTIES PROPERTY TYPE DESCRIPTION AcceptReje

The ForeignKeyConstraint Class

You use an object of the ForeignKeyConstraint class to represent a foreign key constraint between two DataTable objects This ensures that each DataRow in your child DataTable has a matching DataRow in your parent DataTable The ForeignKeyConstraint class is derived from the System.Data.Constraint class Table 12.2 shows the

ForeignKeyConstraint properties

Table 12.2: ForeignKeyConstraint PROPERTIES

PROPERTY TYPE DESCRIPTION

AcceptRejectRule AcceptRejectRule Gets or sets the AcceptRejectRule that indicates

the action that is to take place when the AcceptChanges() method of the DataTable is called

The members of the System.Data.AcceptRejectRule enumeration are

• Cascade, which indicates that the changes

to the DataRow objects in the parent DataTable are also made in the child DataTable

• None, which indicates that no action takes place

The default is None

Columns DataColumn[] Gets the array of DataColumn objects from the

child DataTable

ConstraintName string Gets the name of the UniqueConstraint object DeleteRule Rule Gets or sets the Rule that indicates the action that

is to take place when a DataRow in the parent DataTable is deleted

The members of the System.Data.Rule enumeration are

• Cascade, which indicates that the delete

or update to the DataRow objects in the parent DataTable is also made in the child DataTable

Table 12.2: ForeignKeyConstraint PROPERTIES

PROPERTY TYPE DESCRIPTION

• None, which indicates that no action takes place

• SetDefault, which indicates that the DataColumn values in the child DataTable are to be set to the value in the DefaultValue property of the

DataColumn

• SetNull, which indicates that the DataColumn values in the child DataTable are to be set to DBNull

The default is Cascade

ExtendedProperties PropertyCollection Gets the PropertyCollection object that you can

use to store strings of additional information RelatedColumns DataColumn[] Gets the array of DataColumn objects in the

parent DataTable for the UniqueConstraint RelatedTable DataTable Gets the parent DataTable for the

UniqueConstraint

Table DataTable Gets the child DataTable to which the

UniqueConstraint belongs

UpdateRule Rule Gets or sets the Rule that indicates the action that

is to take place when a DataRow in the parent DataTable is updated See the DeleteRule property for the members of the Rule enumeration

The default is Cascade