我应该在这些样本上实现IDisposable

Question

示例1.（如果我的某个方法使用非托管对象）

Public Class Logger
     'Implements IDisposable <<< is this necessary because of unmanaged object inside the method?

     Public Sub CreateLogFile(ByVal msg As String)
        Try

           If Not String.IsNullOrEmpty(_LogDir) Then
             Try
               Using objWriter As New System.IO.StreamWriter(Format(Now, "MM-dd-yyyy HHmmss") & ".txt", True)
                   objWriter.WriteLine(msg)
                   objWriter.Close()
                End Using
             Catch ex As Exception

             End Try
           End If
        Catch ex As Exception
        End Try
    End Sub

End Class

示例2.（如果我在窗体中声明一个事件）

Public Class frmViewerReport
    'Implements IDisposable <<< is this necessary because of event I added in the winform?

    Public Event DoneAutoPrint()
    Public Event Progress()
    Public Event ProgressDone()
    Public Event ErrorRaised(ByVal msg As String)
End Class

示例3.（如果我的类使用具有基于dbcontext的类的类）

Public Class MyRepository
    'Implements IDisposable <<< is this necessary because of dbcontext?

    Private _ctx As New MyEntities
    Private _User As User
End Class

Public Class MyEntities
    Inherits DbContext
End Class

我知道有很多关于这个问题的话题，我什么时候都找不到具体的样本。

非常感谢您抽出宝贵时间。是/否答案会有所帮助。