Relationships (Metadata)
Relationships in the Entity Data Model (EDM) define how two entities are related. The Entity Data Model Relationships topic provides detailed information about the relationships in the EDM.
The ADO.NET metadata provides an AssociationType to represent the relationships between the EntityTypes. An AssociationType derives from a RelationshipType and represents an EDM association. Similarly, the AssociationSet describes the EntitySets participating in a specific EDM association. For more information about entity and association sets, see Entity Sets (EDM) and Association Sets (EDM).
The following code sample demonstrates how to get a metadata workspace from the connection and then use that metadata workspace to retrieve information about the relationships in the specified model. Note that the metadata workspace is a runtime service component that provides support for retrieving metadata.
The code sample uses a CSpace to specify the model. The CSpace represents the default name for the conceptual model.
The code sample includes three methods: GetAssociations, GetAssociationSets, and GetOneAssociationSet.
The GetAssociations method gets a collection of associations and then iterates through the collection to access their association End members.
The GetAssociationSets method gets a collection of entity containers and then iterates through the collection to get each association set in the specified container. In the EDM, an EntityContainer represents a logical grouping of entity sets and association sets. For more information about how the entity containers are defined in the EDM, see Entity Containers (EDM).
The GetOneAssociationSet method gets a collection of entity containers and then iterates through the collection to get only one association set by using the specified name.
The following code sample uses the Adventureworks Model that is provided in the AdventureWorks Complete Model (EDM) topic. For an example of the application config file, see Using the AdventureWorks Object Model (EDM).
using System;
using System.Data;
using System.Data.EntityClient;
using System.Data.Metadata.Edm;
using System.Collections.ObjectModel;
class GetRelationshipsExample
{
static void Main()
{
try
{
// Establish a connection to the underlying data provider by
// using the connection string specified in the config file.
using (EntityConnection connection =
new EntityConnection("Name=AdventureWorksEntities"))
{
// Open the connection.
connection.Open();
// Access the metadata workspace.
MetadataWorkspace workspace =
connection.GetMetadataWorkspace();
// Get associations from the conceptual model.
GetAssociations(workspace, DataSpace.CSpace);
// Get association sets from the conceptual model.
GetAssociationSets(workspace, DataSpace.CSpace);
// Get one assoiation set by using the specified
// relationship name from the conceptual model.
string relationshipName = "FK_Employee_Contact_ContactID";
GetOneAssociationSet(
workspace, relationshipName, DataSpace.CSpace);
}
}
catch (MetadataException exceptionMetadata)
{
Console.WriteLine("MetadataException: {0}",
exceptionMetadata.Message);
}
catch (System.Data.MappingException exceptionMapping)
{
Console.WriteLine("MappingException: {0}",
exceptionMapping.Message);
}
}
public static void GetAssociations(
MetadataWorkspace workspace, DataSpace model)
{
Console.WriteLine("***Get Associations =>");
// Get a collection of association types.
ReadOnlyCollection<AssociationType> associationTypes =
workspace.GetItems<AssociationType>(model);
// Iterate through the collection to get each association type.
foreach (AssociationType associationType in associationTypes)
{
Console.WriteLine("AssociationType Name: {0}, Namespace: {1}",
associationType.Name,
associationType.NamespaceName);
// Iterate through the collection to get
// each association end member.
foreach (AssociationEndMember end in
associationType.AssociationEndMembers)
{
Console.WriteLine(
"\t End Name: {0}, Type: {1}, Multiplicity: {2}",
end.Name,
end.TypeUsage.EdmType.Name,
end.RelationshipMultiplicity);
}
}
}
public static void GetAssociationSets(
MetadataWorkspace workspace, DataSpace model)
{
Console.WriteLine("***Get Association Sets =>");
// Get a collection of entity containers.
ReadOnlyCollection<EntityContainer> containers =
workspace.GetItems<EntityContainer>(model);
// Iterate through the collection to get each entity container.
foreach (EntityContainer container in containers)
{
// Iterate through the collection to get each entity set base.
foreach (EntitySetBase baseSet in container.BaseEntitySets)
{
// EntitySetBase is a super type for
// AssociationSet and EntitySet.
// Check if the current object is an instance of the
// AssociationSet.
if (baseSet is AssociationSet)
{
Console.WriteLine(
"AssociationSet Name: {0} , " +
"AssociationType Name: {1} ",
baseSet.Name, baseSet.ElementType.FullName);
AssociationSet associationSet =
baseSet as AssociationSet;
// Iterate through the collection to get
// each association end.
foreach (AssociationSetEnd end in
associationSet.AssociationSetEnds)
{
Console.WriteLine(
"EntitySet Name: {0} , Name: {1}, " +
"AssociationEndMember: {2} ",
end.EntitySet,
end.Name,
end.CorrespondingAssociationEndMember);
}
}
}
}
}
public static void GetOneAssociationSet(
MetadataWorkspace workspace, string relationshipName,
DataSpace model)
{
Console.WriteLine("***Get One AssociationSet =>");
// Get a collection of entity containers.
ReadOnlyCollection<EntityContainer> containers =
workspace.GetItems<EntityContainer>(model);
// Iterate through the collection to get each entity container.
foreach (EntityContainer container in containers)
{
RelationshipSet relationshipSet;
// Check if the relationship with the specified name exists
// or not.
if (container.TryGetRelationshipSetByName(
relationshipName, true, out relationshipSet))
{
AssociationSet associationSet =
relationshipSet as AssociationSet;
Console.WriteLine(
"AssociationSet Name: {0} , " +
"AssociationType Name: {1} ",
associationSet.Name,
associationSet.ElementType.FullName);
}
}
}
}
Imports System
Imports System.Collections.ObjectModel
Imports System.Data
Imports System.Data.EntityClient
Imports System.Data.Metadata.Edm
Class GetRelationshipsExample
Shared Sub Main()
Try
' Establish a connection to the underlying data provider by
' using the connection string specified in the config file.
Using connection As EntityConnection = _
New EntityConnection("Name=AdventureWorksEntities")
' Open the conection.
connection.Open()
' Access the metadata workspace.
Dim workspace As MetadataWorkspace = _
connection.GetMetadataWorkspace
' Get associations from the conceptual model.
GetAssociations(workspace, DataSpace.CSpace)
' Get association sets from the conceptual model.
GetAssociationSets(workspace, DataSpace.CSpace)
' Get one assoiation set by using the specified
' relationship name from the conceptual model.
Dim relationshipName As String = _
"FK_Employee_Contact_ContactID"
GetOneAssociationSet( _
workspace, relationshipName, DataSpace.CSpace)
End Using
Catch exceptionMetadata As MetadataException
Console.WriteLine("MetadataException: {0}", _
exceptionMetadata.Message)
Catch exceptionMapping As MappingException
Console.WriteLine("MappingException: {0}", _
exceptionMapping.Message)
End Try
End Sub
Public Shared Sub GetAssociations( _
ByVal workspace As MetadataWorkspace, ByVal model As DataSpace)
Console.WriteLine("***Get Associations =>")
' Get a collection of association types.
Dim associationTypes As ReadOnlyCollection(Of AssociationType) = _
workspace.GetItems(Of AssociationType)(model)
' Iterate through the collection to get each association type.
Dim associationType As AssociationType
For Each associationType In associationTypes
Console.WriteLine("AssociationType Name: {0}, Namespace: {1}", _
associationType.Name, associationType.NamespaceName)
' Iterate through the collection to get
' each association end member.
Dim endMember As AssociationEndMember
For Each endMember In associationType.AssociationEndMembers
Console.WriteLine(ControlChars.Tab & _
" End Name: {0}, Type: {1}, Multiplicity: {2}", _
endMember.Name, endMember.TypeUsage.EdmType.Name, _
endMember.RelationshipMultiplicity)
Next
Next
End Sub
Public Shared Sub GetAssociationSets( _
ByVal workspace As MetadataWorkspace, ByVal model As DataSpace)
Console.WriteLine("***Get Association Sets =>")
' Get a collection of entity containers.
Dim containers As ReadOnlyCollection(Of EntityContainer) = _
workspace.GetItems(Of EntityContainer)(model)
Dim container As EntityContainer
' Iterate through the collection to get each entity container.
For Each container In containers
Dim baseSet As EntitySetBase
' Iterate through the collection to get each entity set base.
For Each baseSet In container.BaseEntitySets
' EntitySetBase is a super type for
' AssociationSet and EntitySet.
' Check if the current object is an instance of the
' AssociationSet.
If TypeOf baseSet Is AssociationSet Then
Console.WriteLine( _
"AssociationSet Name: {0} , AssociationType Name: {1} ", _
baseSet.Name, baseSet.ElementType.FullName)
Dim associationSet As AssociationSet = _
TryCast(baseSet, AssociationSet)
Dim end1 As AssociationSetEnd
' Iterate through the collection to get
' each association end.
For Each end1 In associationSet.AssociationSetEnds
Console.WriteLine( _
"EntitySet Name: {0} , Name: {1}, AssociationEndMember: {2} ", _
end1.EntitySet, end1.Name, _
end1.CorrespondingAssociationEndMember)
Next
End If
Next
Next
End Sub
Public Shared Sub GetOneAssociationSet( _
ByVal workspace As MetadataWorkspace, _
ByVal relationshipName As String, _
ByVal model As DataSpace)
Console.WriteLine("***Get One AssociationSet =>")
' Get a collection of entity containers.
Dim containers As ReadOnlyCollection(Of EntityContainer) = _
workspace.GetItems(Of EntityContainer)(model)
Dim container As EntityContainer
' Iterate through the collection to get each entity container.
For Each container In containers
Dim relationshipSet As RelationshipSet
relationshipSet = Nothing
' Check if the relationship with the specified name exists
' or not.
If container.TryGetRelationshipSetByName( _
relationshipName, True, relationshipSet) Then
Dim associationSet As AssociationSet = _
TryCast(relationshipSet, AssociationSet)
Console.WriteLine( _
"AssociationSet Name: {0} , AssociationType Name: {1} ", _
associationSet.Name, associationSet.ElementType.FullName)
End If
Next
End Sub
End Class