Visual Studio for Mac添加Web引用失败：需前台线程调用DotNetProject_Modified

问题描述 #

我按以下步骤尝试添加Web服务引用：

• 右键点击项目
• 选择“添加Web引用”
• 粘贴WSDL端点地址

点击“确定”时弹出错误提示：

无法添加Web引用：'DotNetProject_Modified'必须在前台线程调用。

我的环境配置：

• Visual Studio for Mac 版本7.5（build 1254）
• NuGet版本4.3.1.4445
• .NET Core运行时版本2.0.5、2.0.0

完整错误日志：

ERROR [2018-05-12 14:00:46Z]: The web reference could not be added System.InvalidOperationException: 'DotNetProject_Modified' must be called on the foreground thread. at Microsoft.CodeAnalysis.Razor.ForegroundDispatcher.AssertForegroundThread (System.String caller) [0x0001f] in C:\BuildAgent\work\9f4c49cb464f2a60\src\Microsoft.CodeAnalysis.Razor.Workspaces\ForegroundDispatcher.cs:24 at Microsoft.VisualStudio.Mac.LanguageServices.Razor.ProjectSystem.RazorProjectHostBase.DotNetProject_Modified (System.Object sender, MonoDevelop.Projects.SolutionItemModifiedEventArgs args) [0x0000e] in C:\BuildAgent\work\9f4c49cb464f2a60\src\Microsoft.VisualStudio.Mac.LanguageServices.Razor\ProjectSystem\RazorProjectHostBase.cs:124 at (wrapper delegate-invoke) <Module>.invoke_void_object_SolutionItemModifiedEventArgs(object,MonoDevelop.Projects.SolutionItemModifiedEventArgs) at MonoDevelop.Projects.SolutionFolderItem.OnModified (MonoDevelop.Projects.SolutionItemModifiedEventArgs args) [0x00016] in /Users/builder/data/lanes/5965/498923ea/source/monodevelop/main/src/core/MonoDevelop.Core/MonoDevelop.Projects/SolutionFolderItem.cs:452 at MonoDevelop.Projects.Project.OnModified (MonoDevelop.Projects.SolutionItemModifiedEventArgs args) [0x0001a] in /Users/builder/data/lanes/5965/498923ea/source/monodevelop/main/src/core/MonoDevelop.Core/MonoDevelop.Projects/Project.cs:408 at MonoDevelop.Projects.SolutionFolderItem.NotifyModified (System.String hint) [0x00000] in /Users/builder/data/lanes/5965/498923ea/source/monodevelop/main/src/core/MonoDevelop.Core/MonoDevelop.Projects/SolutionFolderItem.cs:439 at MonoDevelop.Projects.Project.OnItemsAdded (System.Collections.Generic.IEnumerable`1[T] objs) [0x00075] in /Users/builder/data/lanes/5965/498923ea/source/monodevelop/main/src/core/MonoDevelop.Core/MonoDevelop.Projects/Project.cs:2337 at MonoDevelop.Projects.DotNetProject.OnItemsAdded (System.Collections.Generic.IEnumerable`1[T] objs) [0x00030] in /Users/builder/data/lanes/5965/498923ea/source/monodevelop/main/src/core/MonoDevelop.Core/MonoDevelop.Projects/DotNetProject.cs:1767 at MonoDevelop.Projects.Project+DefaultMSBuildProjectExtension.OnItemsAdded (System.Collections.Generic.IEnumerable`1[T] objs) [0x00000] in /Users/builder/data/lanes/5965/498923ea/source/monodevelop/main/src/core/MonoDevelop.Core/MonoDevelop.Projects/Project.cs:4636 at MonoDevelop.Projects.ProjectExtension.OnItemsAdded (System.Collections.Generic.IEnumerable`1[T] objs) [0x00000] in /Users/builder/data/lanes/5965/498923ea/source/monodevelop/main/src/core/MonoDevelop.Core/MonoDevelop.Projects/ProjectExtension.cs:266 at MonoDevelop.Projects.ProjectExtension.OnItemsAdded (System.Collections.Generic.IEnumerable`1[T] objs) [0x00000] in /Users/builder/data/lanes/5965/498923ea/source/monodevelop/main/src/core/MonoDevelop.Core/MonoDevelop.Projects/ProjectExtension.cs:266 at MonoDevelop.Projects.ProjectExtension.OnItemsAdded (System.Collections.Generic.IEnumerable`1[T] objs) [0x00000] in /Users/builder/data/lanes/5965/498923ea/source/monodevelop/main/src/core/MonoDevelop.Core/MonoDevelop.Projects/ProjectExtension.cs:266 at MonoDevelop.Projects.ProjectExtension.OnItemsAdded (System.Collections.Generic.IEnumerable`1[T] objs) [0x00000] in /Users/builder/data/lanes/5965/498923ea/source/monodevelop/main/src/core/MonoDevelop.Core/MonoDevelop.Projects/ProjectExtension.cs:266 at MonoDevelop.Projects.ProjectExtension.OnItemsAdded (System.Collections.Generic.IEnumerable`1[T] objs) [0x00000] in /Users/builder/data/lanes/5965/498923ea/source/monodevelop/main/src/core/MonoDevelop.Core/MonoDevelop.Projects/ProjectExtension.cs:266 at MonoDevelop.Projects.ProjectExtension.OnItemsAdded (System.Collections.Generic.IEnumerable`1[T] objs) [0x00000] in /Users/builder/data/lanes/5965/498923ea/source/monodevelop/main/src/core/MonoDevelop.Core/MonoDevelop.Projects/ProjectExtension.cs:266 at MonoDevelop.Projects.ProjectExtension.OnItemsAdded (System.Collections.Generic.IEnumerable`1[T] objs) [0x00000] in /Users/builder/data/lanes/5965/498923ea/source/monodevelop/main/src/core/MonoDevelop.Core/MonoDevelop.Projects/ProjectExtension.cs:266

原因分析 #

这是Visual Studio for Mac 7.5版本中Razor语言服务的已知bug：添加Web引用触发项目修改事件时，Razor相关代码试图在后台线程执行必须在前台UI线程运行的操作，导致断言失败抛出错误。

解决方案 #

按优先级推荐以下几种解决办法：

1. 升级Visual Studio for Mac到最新版本
   Microsoft在后续版本（比如8.0及以上）中修复了这个Razor线程问题，升级后可以彻底避免该错误，这是最根本的解决方式。

2. 临时禁用Razor语言服务（紧急场景）
   如果暂时无法升级，可尝试临时禁用Razor相关服务：

   • 打开IDE偏好设置（Visual Studio > Preferences）
   • 导航到Text Editor > Source Code
   • 找到Razor相关选项，取消勾选启用，重启IDE后再尝试添加Web引用。完成操作后可重新启用该服务。

3. 使用.NET CLI命令添加服务引用
   绕开IDE的UI问题，直接用命令行工具添加：

   dotnet svcutil <你的WSDL端点URL>
   

   执行命令后，生成的服务引用文件会自动添加到项目中，后续可在IDE中正常使用。

4. 手动迁移服务引用文件
   也可以在Windows环境下用Visual Studio添加Web引用，生成对应的.cs文件和配置项，再将这些文件复制到Mac上的项目中，手动配置相关引用和设置。

内容的提问来源于stack exchange，提问作者Cristian Kumul