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UniqueConstraint Class
Definition
- Namespace:
- System.Data
- Assemblies:
- netstandard.dll, System.Data.Common.dll
- Assembly:
- System.Data.Common.dll
- Assembly:
- System.Data.dll
- Assembly:
- netstandard.dll
- Source:
- UniqueConstraint.cs
- Source:
- UniqueConstraint.cs
- Source:
- UniqueConstraint.cs
- Source:
- UniqueConstraint.cs
- Source:
- UniqueConstraint.cs
Important
Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.
Represents a restriction on a set of columns in which all values must be unique.
public ref class UniqueConstraint : System::Data::Constraintpublic class UniqueConstraint : System.Data.Constraint[System.Serializable]
public class UniqueConstraint : System.Data.Constrainttype UniqueConstraint = class
inherit Constraint[<System.Serializable>]
type UniqueConstraint = class
inherit ConstraintPublic Class UniqueConstraint
Inherits Constraint- Inheritance
- Attributes
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
| Name | Description |
|---|---|
| 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
| Name | Description |
|---|---|
| _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
| Name | Description |
|---|---|
| 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.
See also
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