Added support for early binding object references. Closes #41.

Utilises the DatabaseObjects.Generic.ObjectReference class in conjunction with the ObjectReferenceEarlyBindingAttribute to indicate that the foreign object should be loaded using a table join and loaded with the containing / referencing object. This avoids having to specify table joins as this is done automatically.

Attributes/ObjectReferenceEarlyBindingAttribute.vb

@@ -0,0 +1,52 @@
+' ___________________________________________________
+'
+'  © Hi-Integrity Systems 2012. All rights reserved.
+'  www.hisystems.com.au - Toby Wicks
+' ___________________________________________________
+'
+
+Option Strict On
+Option Explicit On
+
+''' <summary>
+''' Attribute for a field of type DatabaseObjects.Generic.ObjectReference class.
+''' Attribute cannot be applied to a DatabaseObjects.ObjectReference class - only the generic version.
+''' 
+''' Indicates whether the foreign / referenced object should be loaded when the containing
+''' object is loaded (early binding).
+''' 
+''' If ommitted then the late binding is applied. Specifically, only the reference object's 
+''' distinct value will be assigned to the ObjectReference.DistinctValue property. 
+''' Subsequent calls to ObjectReference.Object will load the foreign / referenced.
+''' 
+''' Early binding is achieved by joining the table with the foreign table and creating
+''' the main object and the foreign / referenced object from the joined data.
+''' The table joins are created automatically and are automatically implemented in the 
+''' DatabaseObjects.TableJoins function.
+''' 
+''' ObjectReferenceEarlyBindingAttribute must be used with the FieldMappingAttribute to indicate 
+''' the name of the field in the primary collection's table that references the 
+''' foreign field / distinct value in the foreign collection.
+''' The field specified MUST link to the foreign collection's distinct field and table name as indicated 
+''' by the TableAttribute and DistinctFieldAttribute values.
+''' </summary>
+''' <remarks>
+''' The foreign collection table is determined by utilising the type T defined by 
+''' DatabaseObjects.Generic.ObjectReference and then obtaining the table name and distinct 
+''' field from the TableAttribute and DistinctFieldAttribute values.
+''' </remarks>
+<AttributeUsage(AttributeTargets.Field, AllowMultiple:=False, Inherited:=True)> _
+Public Class ObjectReferenceEarlyBindingAttribute
+    Inherits Attribute
+
+    ''' <summary>
+    ''' Indicates that the referenced object should be loaded when the main object is loaded.
+    ''' This is achieved using table joins.
+    ''' Can only be used with a DatabaseObjects.Generic.ObjectReference class.
+    ''' The foreign collection must specify the TableAttribute and DistinctFieldAttribute values.
+    ''' </summary>
+    Public Sub New()
+
+    End Sub
+
+End Class

Database/DatabaseObjectUsingAttributesHelper.vb

@@ -8,6 +8,7 @@
 
 Option Strict On
 Option Explicit On
+Option Infer On
 
 ''' --------------------------------------------------------------------------------
 ''' <summary>
@@ -209,10 +210,20 @@ Public Module DatabaseObjectUsingAttributesHelper
             LoadFieldsForBaseTypes(objObject, objType.BaseType, objFields)
             LoadFieldsForObject(objObject, objType, objFields)
             LoadFieldsForHookedObjects(objObject, objType, objFields)
+            LoadFieldsForObjectReferenceEarlyBinding(objObject, objType, objFields)
         End If
 
     End Sub
 
+    Private Sub LoadFieldsForObjectReferenceEarlyBinding(ByVal objectToLoad As Object, ByVal type As System.Type, ByVal fieldValues As SQL.SQLFieldValues)
+
+        For Each earlyBindingField In ObjectReferenceEarlyBinding.GetObjectReferenceEarlyBindingFields(type)
+            Dim objectReference = DirectCast(earlyBindingField.Field.GetValue(objectToLoad), ObjectReference)
+            objectReference.Object = Database.ObjectFromFieldValues(objectReference.ParentCollection, fieldValues)
+        Next
+
+    End Sub
+
     Private Sub LoadFieldsForHookedObjects(ByVal objObject As Object, ByVal objType As System.Type, ByVal objFields As SQL.SQLFieldValues)
 
         Dim objAttributes As Object()

Database/DatabaseObjectsUsingAttributesHelper.vb

@@ -74,20 +74,29 @@ Friend Class DatabaseObjectsUsingAttributesHelper
 
     Public Function ItemInstance() As IDatabaseObject
 
-        Dim itemInstanceType As Type
+        Dim itemInstanceType = GetItemInstanceType()
+
+        Return DatabaseObjectsItemInstance.CreateItemInstance(itemInstanceType, pobjDatabaseObjects)
+
+    End Function
+
+    ''' <summary>
+    ''' Returns the item instance type to instantiate.
+    ''' It may be defined as a T argument on a generic collection or explicitly
+    ''' via the ItemInstance attribute.
+    ''' </summary>
+    Private Function GetItemInstanceType() As Type
 
         If pobjItemInstance Is Nothing Then
             Try
-                itemInstanceType = DatabaseObjectsItemInstance.GetGenericCollectionTArgument(pobjDatabaseObjects.GetType)
+                Return DatabaseObjectsItemInstance.GetGenericCollectionTArgument(pobjDatabaseObjects.GetType)
             Catch ex As Exceptions.DatabaseObjectsException
                 Throw New Exceptions.DatabaseObjectsException("ItemInstanceAttribute has not been specified and " + ex.Message)
             End Try
         Else
-            itemInstanceType = pobjItemInstance.Type
+            Return pobjItemInstance.Type
         End If
 
-        Return DatabaseObjectsItemInstance.CreateItemInstance(itemInstanceType, pobjDatabaseObjects)
-
     End Function
 
     Public ReadOnly Property DistinctFieldName() As String
@@ -185,25 +194,43 @@ Friend Class DatabaseObjectsUsingAttributesHelper
 
     Public Function TableJoins(ByVal objPrimaryTable As SQL.SQLSelectTable, ByVal objTables As SQL.SQLSelectTables) As SQL.SQLSelectTableJoins
 
+        Dim tableJoinsCollection As SQL.SQLSelectTableJoins
+
         'If attribute was not specified 
-        If pobjTableJoins.Count = 0 Then
-            Return Nothing
+        If pobjTableJoins.Count > 0 Then
+            tableJoinsCollection = TableJoinsFromAttributes(pobjTableJoins.ToArray, objPrimaryTable, objTables)
         Else
-            Dim objTableJoins As SQL.SQLSelectTableJoins = New SQL.SQLSelectTableJoins
-            Dim leftTable As SQL.SQLSelectTableBase = objPrimaryTable
-            Dim leftTableName As String = objPrimaryTable.Name
-
-            For Each tableJoinAttribute In pobjTableJoins
-                Dim rightTable As SQL.SQLSelectTableBase = objTables.Add(tableJoinAttribute.ToTableName)
-                Dim tableJoin = objTableJoins.Add(leftTable, SQL.SQLSelectTableJoin.Type.Inner, rightTable)
-                tableJoin.Where.Add(New SQL.SQLFieldExpression(New SQL.SQLSelectTable(leftTableName), tableJoinAttribute.FieldName), SQL.ComparisonOperator.EqualTo, New SQL.SQLFieldExpression(New SQL.SQLSelectTable(tableJoinAttribute.ToTableName), tableJoinAttribute.ToFieldName))
-                leftTable = tableJoin
-                leftTableName = tableJoinAttribute.ToTableName
-            Next
+            'If the ObjectReferenceEarlyBindingAttribute is specified on the item instance then create the table joins that will be required
+            Dim earlyBindingTableJoins = ObjectReferenceEarlyBinding.GetTableJoins(pobjDatabaseObjects, objPrimaryTable, Me.GetItemInstanceType)
 
-            Return objTableJoins
+            If earlyBindingTableJoins.Count > 0 Then
+                tableJoinsCollection = earlyBindingTableJoins
+            Else
+                tableJoinsCollection = Nothing
+            End If
         End If
 
+        Return tableJoinsCollection
+
+    End Function
+
+    Private Shared Function TableJoinsFromAttributes(tableJoinAttributes As TableJoinAttribute(), ByVal primaryTable As SQL.SQLSelectTable, ByVal tables As SQL.SQLSelectTables) As SQL.SQLSelectTableJoins
+
+        Dim tableJoinsCollection As New SQL.SQLSelectTableJoins
+
+        Dim leftTable As SQL.SQLSelectTableBase = primaryTable
+        Dim leftTableName As String = primaryTable.Name
+
+        For Each tableJoinAttribute In tableJoinAttributes
+            Dim rightTable As SQL.SQLSelectTableBase = tables.Add(tableJoinAttribute.ToTableName)
+            Dim tableJoin = tableJoinsCollection.Add(leftTable, SQL.SQLSelectTableJoin.Type.Inner, rightTable)
+            tableJoin.Where.Add(New SQL.SQLFieldExpression(New SQL.SQLSelectTable(leftTableName), tableJoinAttribute.FieldName), SQL.ComparisonOperator.EqualTo, New SQL.SQLFieldExpression(New SQL.SQLSelectTable(tableJoinAttribute.ToTableName), tableJoinAttribute.ToFieldName))
+            leftTable = tableJoin
+            leftTableName = tableJoinAttribute.ToTableName
+        Next
+
+        Return tableJoinsCollection
+
     End Function
 
 

Database/ObjectReference.vb

@@ -179,6 +179,14 @@ Public Class ObjectReference
         End Set
     End Property
 
+    Friend ReadOnly Property ParentCollection As IDatabaseObjects
+        Get
+
+            Return pobjCollection
+
+        End Get
+    End Property
+
     ''' --------------------------------------------------------------------------------
     ''' <summary>
     ''' Returns whether the Object property would return Nothing.