UniqueConstraint Class

Reference

Definition

Namespace:: System.Data

Assembly:: System.Data.Common.dll

Assembly:: System.Data.dll

Assembly:: netstandard.dll

Source:: UniqueConstraint.cs

Source:: UniqueConstraint.cs

Source:: UniqueConstraint.cs

Important

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Represents a restriction on a set of columns in which all values must be unique.

public ref class UniqueConstraint : System::Data::Constraint

public class UniqueConstraint : System.Data.Constraint

[System.Serializable]
public class UniqueConstraint : System.Data.Constraint

type UniqueConstraint = class
    inherit Constraint

[<System.Serializable>]
type UniqueConstraint = class
    inherit Constraint

Public Class UniqueConstraint
Inherits Constraint

Inheritance: Object

Constraint
UniqueConstraint

Attributes: SerializableAttribute

Examples

The following example adds a UniqueConstraint to a DataSet and sets the EnforceConstraints property to true.

Public Sub CreateDataTable()
    Dim dataTable As New DataTable()
    dataTable.Columns.Add("CustomerID", Type.GetType("System.String"))
    dataTable.Columns.Add("CompanyName", Type.GetType("System.String"))

    Dim uniqueConstraint As UniqueConstraint = _
      New UniqueConstraint("CustConstraint", _
      New DataColumn() {dataTable.Columns("CustomerID"), _
      dataTable.Columns("CompanyName")})

    dataTable.Constraints.Add(uniqueConstraint)
End Sub

Remarks

The UniqueConstraint is enforced on a single column (or columns) to ensure that a primary key value is unique.

Constraints are not enforced unless the EnforceConstraints property is set to true.

When the a DataSet is merged with a second DataSet, constraints are not enforced until all merges are completed.

Constructors

UniqueConstraint(DataColumn, Boolean)	Initializes a new instance of the UniqueConstraint class with the DataColumn to constrain, and a value specifying whether the constraint is a primary key.
UniqueConstraint(DataColumn)	Initializes a new instance of the UniqueConstraint class with the specified DataColumn.
UniqueConstraint(DataColumn[], Boolean)	Initializes a new instance of the UniqueConstraint class with an array of DataColumn objects to constrain, and a value specifying whether the constraint is a primary key.
UniqueConstraint(DataColumn[])	Initializes a new instance of the UniqueConstraint class with the given array of DataColumn objects.
UniqueConstraint(String, DataColumn, Boolean)	Initializes a new instance of the UniqueConstraint class with the specified name, the DataColumn to constrain, and a value specifying whether the constraint is a primary key.
UniqueConstraint(String, DataColumn)	Initializes a new instance of the UniqueConstraint class with the specified name and DataColumn.
UniqueConstraint(String, DataColumn[], Boolean)	Initializes a new instance of the UniqueConstraint class with the specified name, an array of DataColumn objects to constrain, and a value specifying whether the constraint is a primary key.
UniqueConstraint(String, DataColumn[])	Initializes a new instance of the UniqueConstraint class with the specified name and array of DataColumn objects.
UniqueConstraint(String, String[], Boolean)	Initializes a new instance of the UniqueConstraint class with the specified name, an array of DataColumn objects to constrain, and a value specifying whether the constraint is a primary key.

Properties

_DataSet	Gets the DataSet to which this constraint belongs. (Inherited from Constraint)
Columns	Gets the array of columns that this constraint affects.
ConstraintName	The name of a constraint in the ConstraintCollection. (Inherited from Constraint)
ExtendedProperties	Gets the collection of user-defined constraint properties. (Inherited from Constraint)
IsPrimaryKey	Gets a value indicating whether or not the constraint is on a primary key.
Table	Gets the table to which this constraint belongs.

Methods

CheckStateForProperty()	Gets the DataSet to which this constraint belongs. (Inherited from Constraint)
Equals(Object)	Compares this constraint to a second to determine if both are identical.
GetHashCode()	Gets the hash code of this instance of the UniqueConstraint object.
GetType()	Gets the Type of the current instance. (Inherited from Object)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
SetDataSet(DataSet)	Sets the constraint's DataSet. (Inherited from Constraint)
ToString()	Gets the ConstraintName, if there is one, as a string. (Inherited from Constraint)

Applies to

Thread Safety

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

Jaa