将 PDFsharp Unprotect 从 C# 转换为 VB.NET答案

【问题标题】：Converting PDFsharp Unprotect from C# to VB.NET将 PDFsharp Unprotect 从 C# 转换为 VB.NET
【发布时间】：2016-02-04 18:52:33
【问题描述】：

我正在尝试将此代码从 PDFsharp 示例转换为 VB.NET，并且我使用了一些转换器，但它一直卡在同一个地方。

这是转换后的代码：

' Get a fresh copy of the sample PDF file.
' The passwords are 'user' and 'owner' in this sample.
Dim filename As String = "HelloWorld (protected).pdf"
File.Copy(Path.Combine("../../../../PDFs/", filename), Path.Combine(Directory.GetCurrentDirectory(), filename), True)

Dim document As PdfDocument

' Opening a document will fail with an invalid password.
Try
    document = PdfReader.Open(filename, "invalid password")
Catch ex As Exception
    Debug.WriteLine(ex.Message)
End Try

' You can specifiy a delegate, which is called if the document needs a
' password. If you want to modify the document, you must provide the
' owner password.
document = PdfReader.Open(filename, PdfDocumentOpenMode.Modify, New PdfPasswordProvider(PasswordProvider))

' Open the document with the user password.
document = PdfReader.Open(filename, "user", PdfDocumentOpenMode.[ReadOnly])

' Use the property HasOwnerPermissions to decide whether the used password
' was the user or the owner password. In both cases PDFsharp provides full
' access to the PDF document. It is up to the programmer who uses PDFsharp
' to honor the access rights. PDFsharp doesn't try to protect the document
' because this make little sence for an open source library.
Dim hasOwnerAccess As Boolean = document.SecuritySettings.HasOwnerPermissions

' Open the document with the owenr password.
document = PdfReader.Open(filename, "owner")
hasOwnerAccess = document.SecuritySettings.HasOwnerPermissions

' A document opened with the owner password is completely unprotected
' and can be modified.
Dim gfx As XGraphics = XGraphics.FromPdfPage(document.Pages(0))
gfx.DrawString("Some text...", New XFont("Times", 12), XBrushes.Firebrick, 50, 100)

' The modified document is saved without any protection applied.
Dim level As PdfDocumentSecurityLevel = document.SecuritySettings.DocumentSecurityLevel

' If you want to save it protected, you must set the DocumentSecurityLevel
' or apply new passwords.
' In the current implementation the old passwords are not automatically
' reused. See 'ProtectDocument' sample for further information.

' Save the document...
document.Save(filename)
' ...and start a viewer.
Process.Start(filename)

它一直卡在这里：document = PdfReader.Open(filename, PdfDocumentOpenMode.Modify, New PdfPasswordProvider(PasswordProvider))

出现此错误.. Delegate 'PdfSharp.PDF.IO.PdfPasswordProvider' 需要一个 'AddressOf' 表达式或 lambda 表达式作为其构造函数的唯一参数

我试过做一个 AddressOf PdfPasswordProvider 但是它不能正常工作。我只是不够先进，无法弄清楚。

编辑 - 代码只是取自 http://www.pdfsharp.com/PDFsharp/index.php?option=com_content&task=view&id=39&Itemid=50

【问题讨论】：

你没有展示PasswordProvider的实现。没有 MCVE 可玩，我不会花时间解决您的问题。
我所拥有的只是它来自的页面：pdfsharp.com/PDFsharp/…
尝试将 AddressOf 放在括号内。很难用您提供的内容来判断，但我认为错误出在 PasswordProvider 参数中，而不是在“New PdfPasswordProvider”声明中。
如果您点击了您找到的页面底部的链接，您会找到带有 PasswordProvider 代码的当前页面：pdfsharp.net/wiki/UnprotectDocument-sample.ashx

标签： vb.net pdfsharp

【解决方案1】：

密码提供程序必须是一个方法（委托） - 需要密码时 PDFsharp 将调用的方法。

网站只显示一个代码sn-p。

您可以在 CodePlex 上找到完整的源代码：
http://pdfsharp.codeplex.com/releases/view/618773

下载源代码包，您将拥有完整的源代码，包括密码提供程序方法。

【讨论】：