iText7更新后实例化PdfDocument遇System.TypeInitializationException求助

最近更新iText7后，原本正常运行的代码在创建PdfDocument实例时抛出System.TypeInitializationException异常。最内层异常为FileNotFoundException，提示无法加载程序集Microsoft.Extensions.Logging, Version=5.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60或其依赖项，系统找不到指定文件。

已确认项目引用了Microsoft.Extensions.Logging 5.0.0版本的包，且文件确实存在。代码运行在基于.NET Framework 4.8的Windows Forms应用中，D:\temp为有权限访问的有效文件夹。

报错代码片段 #

public static void CreatePDF(InvoiceModel model, string outFilePath)
{
    using (PdfWriter writer = new PdfWriter(outFilePath))
    {
        PdfDocument pdf = new PdfDocument(writer);
        Document document = new Document(pdf);

outFilePath 值 #

outFilePath "d:\\temp\\Statement-WTCC-20221117.pdf" string

完整异常信息 #

System.TypeInitializationException
  HResult=0x80131534
  Message=The type initializer for 'iText.Commons.Actions.EventManager' threw an exception.
  Source=itext.kernel
  StackTrace:
   at iText.Kernel.Pdf.PdfDocument.Open(PdfVersion newPdfVersion)
   at LabBilling.Core.InvoicePrint.CreatePDF(InvoiceModel model, String outFilePath) in D:\users\bpowers\source\repos\Lab-Billing\LabBilling Library\BusinessLogic\InvoicePrint.cs:line 33
   at LabBilling.Core.ClientInvoices.GenerateStatement(String clientMnemonic, DateTime asOfDate) in D:\users\bpowers\source\repos\Lab-Billing\LabBilling Library\BusinessLogic\ClientInvoices.cs:line 108
   at LabBilling.Forms.ClientInvoiceForm.generateStatementButton_Click(Object sender, EventArgs e) in D:\users\bpowers\source\repos\Lab-Billing\Lab Billing UI\Forms\ClientInvoiceForm.cs:line 413
   at System.Windows.Forms.Control.OnClick(EventArgs e)
   at System.Windows.Forms.Button.OnClick(EventArgs e)
   at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
   at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.ButtonBase.WndProc(Message& m)
   at System.Windows.Forms.Button.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

Inner Exception 1:
TypeInitializationException: The type initializer for 'iText.Commons.Actions.ProductEventHandler' threw an exception.

Inner Exception 2:
TypeInitializationException: The type initializer for 'iText.Commons.ITextLogManager' threw an exception.

Inner Exception 3:
FileNotFoundException: Could not load file or assembly 'Microsoft.Extensions.Logging, Version=6.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60' or one of its dependencies. The system cannot find the file specified.

Inner Exception 4:
FileNotFoundException: Could not load file or assembly 'Microsoft.Extensions.Logging, Version=5.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60' or one of its dependencies. The system cannot find the file specified.

解决思路 #

• 添加程序集绑定重定向：从异常链可见，iText7尝试加载6.0.0.0版本的日志组件，但项目引用的是5.0.0.0。在App.config中添加绑定规则，强制框架使用已安装的版本：

  <configuration>
    <runtime>
      <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
        <dependentAssembly>
          <assemblyIdentity name="Microsoft.Extensions.Logging" publicKeyToken="adb9793829ddae60" culture="neutral" />
          <bindingRedirect oldVersion="0.0.0.0-6.0.0.0" newVersion="5.0.0.0" />
        </dependentAssembly>
      </assemblyBinding>
    </runtime>
  </configuration>
  

• 清理重建项目：删除项目的bin和obj目录，重新生成解决方案，确保所有依赖包正确复制到输出文件夹。
• 检查依赖完整性：确认Microsoft.Extensions.Logging的间接依赖（如Microsoft.Extensions.DependencyInjection.Abstractions）是否已正确安装，版本需与5.0.0匹配，避免缺失依赖项。
• 调整版本兼容性：尝试降级iText7到之前可用的版本，或者升级Microsoft.Extensions.Logging到6.0.0版本（需确认该版本与.NET Framework 4.8兼容）。
• 验证输出文件：检查项目输出目录中是否存在Microsoft.Extensions.Logging.dll，且版本为5.0.0.0；若缺失，检查NuGet包的“复制本地”属性是否设为True。

内容的提问来源于stack exchange，提问作者BradP