UniqueConstraint Class
Represents a restriction on a set of columns in which all values must be unique.
Assembly: System.Data (in System.Data.dll)
| Name | Description | |
|---|---|---|
![]() | 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 the DataColumn to constrain, and a value specifying whether the constraint is a primary key. |
![]() | UniqueConstraint(array<DataColumn^>^) | Initializes a new instance of the UniqueConstraint class with the given array of DataColumn objects. |
![]() | UniqueConstraint(array<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(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, the DataColumn to constrain, and a value specifying whether the constraint is a primary key. |
![]() | UniqueConstraint(String^, array<DataColumn^>^) | Initializes a new instance of the UniqueConstraint class with the specified name and array of DataColumn objects. |
![]() | UniqueConstraint(String^, array<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^, array<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. |
| Name | Description | |
|---|---|---|
![]() | _DataSet | This API supports the product infrastructure and is not intended to be used directly from your code. 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.(Overrides Constraint::Table.) |
| Name | Description | |
|---|---|---|
![]() | CheckStateForProperty() | This API supports the product infrastructure and is not intended to be used directly from your code. 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.(Overrides Object::Equals(Object^).) |
![]() | Finalize() | Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.) |
![]() | GetHashCode() | Gets the hash code of this instance of the UniqueConstraint object.(Overrides Object::GetHashCode().) |
![]() | GetType() | |
![]() | MemberwiseClone() | |
![]() | SetDataSet(DataSet^) | Sets the constraint's DataSet.(Inherited from Constraint.) |
![]() | ToString() | Gets the ConstraintName, if there is one, as a string.(Inherited from Constraint.) |
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.
The following example adds a UniqueConstraint to a DataSet and sets the EnforceConstraints property to true.
Public Sub CreateDataTable() Dim dataTable As DataTable = 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
Available since 1.1
This type is suitable for multithreaded read operations. You must synchronize any write operations.



