ConstraintCollection Class

 

Represents a collection of constraints for a DataTable.

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

System.Object
  System.Data.InternalDataCollectionBase
    System.Data.ConstraintCollection

[<Sealed>]
type ConstraintCollection = 
    class
        inherit InternalDataCollectionBase
    end

NameDescription
System_CAPS_pubpropertyCount

Gets the total number of elements in a collection.(Inherited from InternalDataCollectionBase.)

System_CAPS_pubpropertyIsReadOnly

Gets a value that indicates whether the InternalDataCollectionBase is read-only.(Inherited from InternalDataCollectionBase.)

System_CAPS_pubpropertyIsSynchronized

Gets a value that indicates whether the InternalDataCollectionBase is synchonized.(Inherited from InternalDataCollectionBase.)

System_CAPS_pubpropertyItem(Int32)

Gets the Constraint from the collection at the specified index.

System_CAPS_pubpropertyItem(String)

Gets the Constraint from the collection with the specified name.

System_CAPS_pubpropertySyncRoot

Gets an object that can be used to synchronize the collection.(Inherited from InternalDataCollectionBase.)

NameDescription
System_CAPS_pubmethodAdd(Constraint)

Adds the specified Constraint object to the collection.

System_CAPS_pubmethodAdd(String, DataColumn, Boolean)

Constructs a new UniqueConstraint with the specified name, DataColumn, and value that indicates whether the column is a primary key, and adds it to the collection.

System_CAPS_pubmethodAdd(String, DataColumn, DataColumn)

Constructs a new ForeignKeyConstraint with the specified name, parent column, and child column, and adds the constraint to the collection.

System_CAPS_pubmethodAdd(String, DataColumn[], Boolean)

Constructs a new UniqueConstraint with the specified name, array of DataColumn objects, and value that indicates whether the column is a primary key, and adds it to the collection.

System_CAPS_pubmethodAdd(String, DataColumn[], DataColumn[])

Constructs a new ForeignKeyConstraint, with the specified arrays of parent columns and child columns, and adds the constraint to the collection.

System_CAPS_pubmethodAddRange(Constraint[])

Copies the elements of the specified ConstraintCollection array to the end of the collection.

System_CAPS_pubmethodCanRemove(Constraint)

Indicates whether a Constraint can be removed.

System_CAPS_pubmethodClear()

Clears the collection of any Constraint objects.

System_CAPS_pubmethodContains(String)

Indicates whether the Constraint object specified by name exists in the collection.

System_CAPS_pubmethodCopyTo(Array, Int32)

Copies all the elements of the current InternalDataCollectionBase to a one-dimensional Array, starting at the specified InternalDataCollectionBase index.(Inherited from InternalDataCollectionBase.)

System_CAPS_pubmethodCopyTo(Constraint[], Int32)

Copies the collection objects to a one-dimensional Array instance starting at the specified index.

System_CAPS_pubmethodEquals(Object)

Determines whether the specified object is equal to the current object.(Inherited from Object.)

System_CAPS_pubmethodGetEnumerator()

Gets an IEnumerator for the collection.(Inherited from InternalDataCollectionBase.)

System_CAPS_pubmethodGetHashCode()

Serves as the default hash function. (Inherited from Object.)

System_CAPS_pubmethodGetType()

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

System_CAPS_pubmethodIndexOf(Constraint)

Gets the index of the specified Constraint.

System_CAPS_pubmethodIndexOf(String)

Gets the index of the Constraint specified by name.

System_CAPS_pubmethodRemove(Constraint)

Removes the specified Constraint from the collection.

System_CAPS_pubmethodRemove(String)

Removes the Constraint object specified by name from the collection.

System_CAPS_pubmethodRemoveAt(Int32)

Removes the Constraint object at the specified index from the collection.

System_CAPS_pubmethodToString()

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

NameDescription
System_CAPS_pubeventCollectionChanged

Occurs whenever the ConstraintCollection is changed because of Constraint objects being added or removed.

NameDescription
System_CAPS_pubmethodAsParallel()

Overloaded. Enables parallelization of a query.(Defined by ParallelEnumerable.)

System_CAPS_pubmethodAsQueryable()

Overloaded. Converts an IEnumerable to an IQueryable.(Defined by Queryable.)

System_CAPS_pubmethodCast<'TResult>()

Casts the elements of an IEnumerable to the specified type.(Defined by Enumerable.)

System_CAPS_pubmethodOfType<'TResult>()

Filters the elements of an IEnumerable based on a specified type.(Defined by Enumerable.)

The ConstraintCollection is accessed through the DataTable.Constraints property.

The ConstraintCollection can contain both UniqueConstraint and ForeignKeyConstraint objects for the DataTable. A UniqueConstraint object makes sure that data in a specific column is always unique to preserve the data integrity. The ForeignKeyConstraint determines what will occur in related tables when data in the DataTable is either updated or deleted. For example, if a row is deleted, the ForeignKeyConstraint will determine whether the related rows are also deleted (a cascade), or some other course of action.

System_CAPS_noteNote

When you add a DataRelation that creates a relationship between two tables to a DataSet, both a ForeignKeyConstraint and a UniqueConstraint are created automatically. The UniqueConstraint is applied to the primary key column in the parent DataTable, and the constraint is added to that table's ConstraintCollection. The ForeignKeyConstraint is applied to the primary key column and the foreign key column, and the constraint is added to the child table's ConstraintCollection.

The ConstraintCollection uses standard collection methods such as Add, Clear, and Remove. In addition, the Contains method can be used to look for the existence of a particular constraint in the collection.

A UniqueConstraint is created when a DataColumn with its Unique property set to true is added to a DataTable object's DataColumnCollection.

A ForeignKeyConstraint is created when a DataRelation is added to a DataSet object's DataRelationCollection.

The first example creates a DataTable, and adds a DataColumn (with its Unique property set to true) to the DataColumnCollection. The second example creates a DataSet, two DataTable objects, four columns, and a DataRelation. The count of constraints is then printed to show that a ForeignKeyConstraint and a UniqueConstraint are created when a DataRelation is added to the DataSet object's DataRelationCollection.

No code example is currently available or this language may not be supported.

.NET Framework
Available since 1.1

This type is safe for multithreaded read operations. You must synchronize any write operations.

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