Index: ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityZeroState.vb
===================================================================
diff -u
--- ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityZeroState.vb	(revision 0)
+++ ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityZeroState.vb	(revision 1729)
@@ -0,0 +1,13 @@
+Public Class ActivityZeroState
+    Inherits ActivityState
+
+    'Can't go from another state into this one.
+    Public Sub New(activity As IActivity)
+        Me.Activity = activity
+    End Sub
+
+    ''' <inheritdoc/>
+    Public Overrides Function ActivityStateEnum() As ActivityStateEnum
+        Return ActiviteitenOpvolging.ActivityStateEnum.Zero
+    End Function
+End Class
Index: ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/IActivityActions.vb
===================================================================
diff -u
--- ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/IActivityActions.vb	(revision 0)
+++ ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/IActivityActions.vb	(revision 1729)
@@ -0,0 +1,19 @@
+Public Interface IActivityActions
+    ''' <summary>
+    ''' The employee starts the activity.
+    ''' </summary>
+    ''' <param name="employee"></param>
+    Sub StartActivity(employee As IEmployee)
+
+    ''' <summary>
+    ''' The employee stops the activity.
+    ''' </summary>
+    ''' <param name="employee"></param>
+    Sub StopActivity(employee As IEmployee)
+
+    ''' <summary>
+    ''' The employee finishes the activity.
+    ''' </summary>
+    ''' <param name="employee"></param>
+    Sub FinishActivity(employee As IEmployee)
+End Interface
Index: ActiviteitenOpvolging/ActiviteitenOpvolging/ActiviteitenOpvolging.vbproj.DotSettings
===================================================================
diff -u -r1717 -r1729
--- ActiviteitenOpvolging/ActiviteitenOpvolging/ActiviteitenOpvolging.vbproj.DotSettings	(.../ActiviteitenOpvolging.vbproj.DotSettings)	(revision 1717)
+++ ActiviteitenOpvolging/ActiviteitenOpvolging/ActiviteitenOpvolging.vbproj.DotSettings	(.../ActiviteitenOpvolging.vbproj.DotSettings)	(revision 1729)
@@ -2,7 +2,9 @@
 	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=configs/@EntryIndexedValue">False</s:Boolean>
 	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=domain/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=domain_005Cclasses/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=domain_005Cclasses_005Cactivity_0020state/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=domain_005Cclasses_005Cimplementations/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=domain_005Cclasses_005Cimplementations_005Cactivity_0020state/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=domain_005Ccontrollers/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=domain_005Cmanagers/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=domain_005Cmanagers_005Cimplementations/@EntryIndexedValue">True</s:Boolean>
Index: ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityStartedState.vb
===================================================================
diff -u
--- ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityStartedState.vb	(revision 0)
+++ ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityStartedState.vb	(revision 1729)
@@ -0,0 +1,27 @@
+Public Class ActivityStartedState
+    inherits ActivityState
+
+    Private ReadOnly _employee As IEmployee
+
+    'Not from other state.
+    Public Sub New(activity As IActivity, employee As IEmployee)
+        Me.Activity = activity
+        _employee = employee
+    End Sub
+
+    'From other state.
+    Public Sub New(state As ActivityState, employee As IEmployee)
+        Activity = state.Activity
+        _employee = employee
+    End Sub
+
+    ''' <inheritdoc/>
+    Public Overrides Function ActivityStateEnum() As ActivityStateEnum
+        Return ActiviteitenOpvolging.ActivityStateEnum.Started
+    End Function
+
+    ''' <inheritdoc/>
+    Public Overrides Function GetEmployee() As IEmployee
+        Return _employee
+    End Function
+End Class
Index: ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/Activity.vb
===================================================================
diff -u -r1727 -r1729
--- ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/Activity.vb	(.../Activity.vb)	(revision 1727)
+++ ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/Activity.vb	(.../Activity.vb)	(revision 1729)
@@ -1,9 +1,10 @@
 Public Class Activity
-    implements IActivity
+    Implements IActivity
     Public Property Id As String Implements IActivity.Id
     Public Property QuantityToProduce As Integer Implements IActivity.QuantityToProduce
     Public Property Label As String Implements IActivity.Label
     Public Property Status As ActivityStateEnum Implements IActivity.Status
+    'todo get enum state from state
     Public Property IsReadOnly As Boolean Implements IActivity.IsReadOnly
     Public Property StartBeforeTimestamp As DateTime Implements IActivity.StartBeforeTimestamp
     Public Property StartAlmostTimeStamp As DateTime Implements IActivity.StartAlmostTimeStamp
@@ -12,4 +13,27 @@
     Public Property EmployeeInitials As String Implements IActivity.EmployeeInitials
 
     Public Property WorkItem As IWorkItem Implements IActivity.WorkItem
+
+    Public Property State As ActivityState Implements IActivity.State
+
+    Public ReadOnly Property CurrentEmployee As IEmployee Implements IActivity.CurrentEmployee
+        Get
+            Return State.GetEmployee()
+        End Get
+    End Property
+
+    ''' <inheritdoc/>
+    Public Sub StartActivity(employee As IEmployee) Implements IActivityActions.StartActivity
+        State.StartActivity(employee)
+    End Sub
+
+    ''' <inheritdoc/>
+    Public Sub StopActivity(employee As IEmployee) Implements IActivityActions.StopActivity
+        State.StopActivity(employee)
+    End Sub
+
+    ''' <inheritdoc/>
+    Public Sub FinishActivity(employee As IEmployee) Implements IActivityActions.FinishActivity
+        State.FinishActivity(employee)
+    End Sub
 End Class
Index: ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/IActivity.vb
===================================================================
diff -u -r1728 -r1729
--- ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/IActivity.vb	(.../IActivity.vb)	(revision 1728)
+++ ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/IActivity.vb	(.../IActivity.vb)	(revision 1729)
@@ -1,4 +1,6 @@
 Public Interface IActivity
+    inherits IActivityActions
+
     Property Id As String
     Property QuantityToProduce As Integer
     Property Label As String
@@ -10,4 +12,7 @@
     Property StartTimeStamp As DateTime
 
     Property WorkItem As IWorkItem
+
+    Property State As ActivityState
+    ReadOnly Property CurrentEmployee As IEmployee
 End interface
Index: ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityState.vb
===================================================================
diff -u
--- ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityState.vb	(revision 0)
+++ ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityState.vb	(revision 1729)
@@ -0,0 +1,30 @@
+Public MustInherit Class ActivityState
+    Implements IActivityActions
+
+    Public Activity As IActivity
+
+    ''' <summary>
+    ''' The <see cref="ActivityStateEnum"/> for the current state.
+    ''' </summary>
+    ''' <returns></returns>
+    Public MustOverride Function ActivityStateEnum() As ActivityStateEnum
+
+    Public Overridable Function GetEmployee() As IEmployee
+        Throw New Exception("No employee present.")
+    End Function
+
+    ''' <inheritdoc/>
+    Public Overridable Sub StartActivity(employee As IEmployee) Implements IActivityActions.StartActivity
+        Throw New Exception("Can't start the activity in this state.")
+    End Sub
+
+    ''' <inheritdoc/>
+    Public Overridable Sub StopActivity(employee As IEmployee) Implements IActivityActions.StopActivity
+        Throw New Exception("Can't stop the activity in this state.")
+    End Sub
+
+    ''' <inheritdoc/>
+    Public Overridable Sub FinishActivity(employee As IEmployee) Implements IActivityActions.FinishActivity
+        Throw New Exception("Can't finish the activity in this state.")
+    End Sub
+End Class
Index: ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityDefaultedState.vb
===================================================================
diff -u
--- ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityDefaultedState.vb	(revision 0)
+++ ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityDefaultedState.vb	(revision 1729)
@@ -0,0 +1,20 @@
+Public Class ActivityDefaultedState
+    Inherits ActivityState
+
+    'Not from other state.
+    Public Sub New(activity As IActivity)
+        Me.Activity = activity
+    End Sub
+
+    ''' <inheritdoc/>
+    Public Overrides Function ActivityStateEnum() As ActivityStateEnum
+        Return ActiviteitenOpvolging.ActivityStateEnum.Defaulted
+    End Function
+
+    ''' <inheritdoc/>
+    Public Overrides Sub StartActivity(employee As IEmployee)
+        'Change state.
+        Activity.State = New ActivityStartedState(Me, employee)
+    End Sub
+
+End Class