Question

我将自定义属性应用于CRUD存储库方法以控制访问：

Public Class SecureDbContextGenericRepository(Of TEntity As Class, TContext As DbContext)
  Inherits DbContextGenericRepository(Of TEntity, TContext)
  Public Sub New(connectionService As IConnectionService)
    MyBase.New(connectionService)
  End Sub
  <EmployeeRoleRequirement(SecurityAction.Demand, EmployeeRoles:=EmployeeRoles.DataWriter)>
  Public Overrides Sub Delete(ParamArray entities() As TEntity)
    MyBase.Delete(entities)
  End Sub
  <EmployeeRoleRequirement(SecurityAction.Demand, EmployeeRoles:=EmployeeRoles.DataWriter)>
  Public Overrides Sub Insert(ParamArray entities() As TEntity)
    MyBase.Insert(entities)
  End Sub
  <EmployeeRoleRequirement(SecurityAction.Demand, EmployeeRoles:=EmployeeRoles.DataReader)>
  Public Overrides Function [Select](Optional predicate As Func(Of TEntity, Boolean) = Nothing) As IList(Of TEntity)
    Return MyBase.Select(predicate)
  End Function
  <EmployeeRoleRequirement(SecurityAction.Demand, EmployeeRoles:=EmployeeRoles.DataWriter)>
  Public Overrides Sub Update(ParamArray entities() As TEntity)
    MyBase.Update(entities)
  End Sub
End Class

这是属性的实现：

Public Class EmployeeRoleRequirementAttribute
    Inherits CodeAccessSecurityAttribute
    Public Sub New(action As SecurityAction)
      MyBase.New(action)
    End Sub

    Public Overrides Function CreatePermission() As IPermission
      Return New EmployeeRolePermission(_EmployeeRoles)
    End Function

    Public Property EmployeeRoles As EmployeeRoles
  End Class  

<Flags>
  Public Enum EmployeeRoles As Integer
    DataReader = 0
    DataWriter = 1
  End Enum

许可：

Public Class EmployeeRolePermission
    Implements IPermission
    Public Sub New(employeeRoles As EmployeeRoles)
      _EmployeeRoles = employeeRoles
    End Sub

    Public Function Copy() As IPermission Implements IPermission.Copy
      Return New EmployeeRolePermission(_EmployeeRoles)
    End Function
    Public Sub Demand() Implements IPermission.Demand
      Dim principal = DirectCast(Thread.CurrentPrincipal, ProductionAssistantPrincipal)
      If Not principal.IsInRole(_EmployeeRoles) Then
        Throw New SecurityException(String.Format(My.Resources.EmployeeRoleNotFound,
                                                  principal.Identity.Name,
                                                  _EmployeeRoles.ToString()))
      End If
    End Sub
    Public Sub FromXml(e As SecurityElement) Implements ISecurityEncodable.FromXml
      Throw New NotImplementedException()
    End Sub
    Public Function Intersect(target As IPermission) As IPermission Implements IPermission.Intersect
      Return New EmployeeRolePermission(_EmployeeRoles And DirectCast(target, EmployeeRolePermission).EmployeeRoles)
    End Function
    Public Function IsSubsetOf(target As IPermission) As Boolean Implements IPermission.IsSubsetOf
      Return _EmployeeRoles.HasFlag(DirectCast(target, EmployeeRolePermission).EmployeeRoles)
    End Function
    Public Function ToXml() As SecurityElement Implements ISecurityEncodable.ToXml
      Throw New NotImplementedException()
    End Function
    Public Function Union(target As IPermission) As IPermission Implements IPermission.Union
      Return New EmployeeRolePermission(_EmployeeRoles Or DirectCast(target, EmployeeRolePermission).EmployeeRoles)
    End Function

    Public ReadOnly Property EmployeeRoles As EmployeeRoles
  End Class

每次到达其中一个CRUD方法时，都会抛出TypeLoadException。我真的不知道原因，但如果我从CRUD方法中删除属性，一切正常。

Answer 1

这似乎是由于属性上的枚举值属性（有关详细信息，请参阅https://connect.microsoft.com/VisualStudio/feedback/details/596251/custom-cas-attributes-with-an-enum-property-set-cause-a-typeloadexception）。要解决此问题，可以在属性上使用字符串值属性，并在属性设置器中或在创建权限之前强制转换为枚举。（就个人而言，我可能会选择前者，以便能够进行早期验证，但是ymmv ...）

Answer 2

另一种解决方法是创建type的属性属性，该属性在Enum中使用，在本例中为Integer。

Public Class EmployeeRoleRequirementAttribute
  Inherits CodeAccessSecurityAttribute
  Public Sub New(action As SecurityAction)
    MyBase.New(action)
  End Sub
  Public Overrides Function CreatePermission() As IPermission
    Return New EmployeeRolePermission(CType(_RequiredEmployeeRoles, EmployeeRoles))
  End Function

  Public Property RequiredEmployeeRoles As Integer
End Class

<Flags>
Public Enum EmployeeRoles As Integer
  DataReader = 0
  DataWriter = 1
End Enum

然后你不需要使用String，它在使用属性时不允许轻松组合标志：

<EmployeeRoleRequirement(SecurityAction.Demand, RequiredEmployeeRoles:=EmployeeRoles.DataReader Or EmployeeRoles.DataWriter)>
Sub SecuredMethod()
End Sub

CodeAccessSecurityAttribute派生类抛出System.TypeLoadException（加载类型时发生失败）

2 个答案: