Connect reusable ASP.NET WebControl to a method for loading data
I'm trying to create a control that can extend other webcontrols and set some properties like visible and enabled, based on user permissions.
Here's an example where your user role would need to include the "CanSave" permission:
<asp:Button ID="btn1" runat="server" Text="Save"/>
<myControls:PermissionsExtender runat="server" ControlToSet="btn1" Permission="CanSave"/>
I'm trying to keep this reusable, that's why the PermissionExtender is in a separate project that can not have any dependencies to other projects. To make a decision, the control of course needs to get this info from somewhere else (database or something). I made another control and, using events, the above extender will be set by a master control, so only that needs to know where to look up the information.
The master control now needs to be configured to know where the information about roles and permissions will be coming from. My idea was to have an interface inside the reusable project, and implement that somewhere else, then configure my control to go and find the cl开发者_开发问答ass that implements the method I need and load it through reflection. But I'm unclear how this could work. I would probably place the master control in the masterpage and supply it a class name like PermissionClass="SecurityLibrary.PermissionsClass". Kinda like ObjectDatasource does it, but other suggestions are welcome.
The method signature would be like:
bool HasPermission(string permission)
It would know the current users role and using that combination, looks up if the role includes the permission.
How can I wire up a call from the control to a method inside my main project that can supply the necessary information without making them dependent.
I think I've got something that will work for you (tested fine for me but I may have misunderstood part of what you were looking for). With this implementation the asp.net designer code will look like this:
<web:PermissionMasterControl runat="server" ID="masterController" PermissionClass="SecurityLibrary.RandomPermissionClass" />
<asp:Button ID="btnSave" runat="server" Text="save" />
<web:PermissionExtender runat="server" ControlToSet="btnSave" Permission="CanSave" MasterControllerID="masterController" />
Now for the SecurityLibrary. Pretty straight forward, I included a simple "RandomPermissionClass" that randomly returns true/false.
Namespace SecurityLibrary
Public MustInherit Class PermissionClass
Public MustOverride Function HasPermission(ByVal permission As String) As Boolean
End Class
Public Class RandomPermissionClass
Inherits PermissionClass
Private rand As New Random()
Public Overrides Function HasPermission(permission As String) As Boolean
Return If(rand.Next(2) = 0, False, True)
End Function
End Class
End Namespace
Now we have the "myControls" library, which contains no references to SecurityLibrary. I created two controls and a delegate. The controls are "PermissionMasterControl" and "PermissionExtender". The delegate is what is used to actually perform the check against the reflected object.
Namespace myControls
Public Delegate Function HasPermissionDelegate(ByVal permission As String) As Boolean
Public Class PermissionMasterControl
Inherits System.Web.UI.Control
Public Property PermissionClass As String
Get
Return If(ViewState("PermissionClass") Is Nothing, "", ViewState("PermissionClass").ToString())
End Get
Set(value As String)
ViewState("PermissionClass") = value
End Set
End Property
Private ReadOnly Property PermissionDelegate As HasPermissionDelegate
Get
If _permissionDel Is Nothing Then
If Not String.IsNullOrEmpty(PermissionClass) Then
Dim t = Type.GetType(PermissionClass, False)
If t IsNot Nothing Then
_permissionObj = Activator.CreateInstance(t)
Dim mi As MethodInfo = _
t.GetMethod("HasPermission", BindingFlags.Public Or BindingFlags.Instance)
_permissionDel = [Delegate].CreateDelegate(GetType(HasPermissionDelegate), _permissionObj, mi)
End If
End If
End If
Return _permissionDel
End Get
End Property
Private _permissionObj As Object = Nothing
Private _permissionDel As HasPermissionDelegate = Nothing
Public Function HasPermission(ByVal permission As String) As Boolean
If PermissionDelegate Is Nothing Then
Throw New NullReferenceException("The specified permission class (" + PermissionClass + ") could not be loaded/found.")
End If
Return PermissionDelegate(permission)
End Function
End Class
Public Class PermissionExtender
Inherits System.Web.UI.Control
Public Property ControlToSet As String
Get
Return If(ViewState("ControlToSet") Is Nothing, "", ViewState("ControlToSet").ToString())
End Get
Set(value As String)
ViewState("ControlToSet") = value
End Set
End Property
Public Property Permission As String
Get
Return If(ViewState("Permission") Is Nothing, "", ViewState("Permission").ToString())
End Get
Set(value As String)
ViewState("Permission") = value
End Set
End Property
Public Property MasterControllerID As String
Get
Return If(ViewState("MasterControllerID") Is Nothing, "", ViewState("MasterControllerID").ToString())
End Get
Set(value As String)
ViewState("MasterControllerID") = value
End Set
End Property
Protected ReadOnly Property MasterController As PermissionMasterControl
Get
If _mastercontroller Is Nothing Then
_mastercontroller = Me.Page.FindControl(MasterControllerID)
End If
Return _mastercontroller
End Get
End Property
Protected ReadOnly Property ManagedControl As Control
Get
If _controlToSet Is Nothing Then
_controlToSet = Me.NamingContainer.FindControl(ControlToSet)
End If
Return _controlToSet
End Get
End Property
Private _controlToSet As Control = Nothing
Private _mastercontroller As PermissionMasterControl = Nothing
Protected Overrides Sub OnLoad(e As System.EventArgs)
MyBase.OnLoad(e)
Dim bResult As Boolean = MasterController.HasPermission(Permission)
ManagedControl.Visible = bResult
End Sub
End Class
End Namespace
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