ASP.Net error

Question

I have a project in ASP.Net, and until now it was runninig fine. Suddenly, I started getting the following error message regarding Microsoft.CSharp, Version=4.0.0.0.

I downloaded the Microsoft.CSharp, and added it to the Nuget Package Manager, and it was accepted, but I am still getting the same error message, as follows:

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Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.8.9282.0

"Could not load file or assembly 'Microsoft.CSharp, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.

__Description:__An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. __Exception Details:__System.IO.FileNotFoundException: Could not load file or assembly 'Microsoft.CSharp, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified. Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.
An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

__Assembly Load Trace:__The following information can be helpful to determine why the assembly 'Microsoft.CSharp, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' could not be loaded.

|WRN: Assembly binding logging is turned OFF.
To enable assembly bind failure logging, set the registry value [HKLM\Software\Microsoft\Fusion!EnableLog] (DWORD) to 1.
Note: There is some performance penalty associated with assembly bind failure logging.
To turn this feature off, remove the registry value [HKLM\Software\Microsoft\Fusion!EnableLog].| | -------- | |WRN: Assembly binding logging is turned OFF. To enable assembly bind failure logging, set the registry value [HKLM\Software\Microsoft\Fusion!EnableLog] (DWORD) to 1. Note: There is some performance penalty associated with assembly bind failure logging. To turn this feature off, remove the registry value [HKLM\Software\Microsoft\Fusion!EnableLog].|

Stack Trace:

|[FileNotFoundException: Could not load file or assembly 'Microsoft.CSharp, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.]

[FileNotFoundException: Could not load file or assembly 'Microsoft.CSharp, Version=8.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.]
System.Reflection.RuntimeAssembly._nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, RuntimeAssembly locationHint, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks) +0
System.Reflection.RuntimeAssembly.InternalLoadAssemblyName(AssemblyName assemblyRef, Evidence assemblySecurity, RuntimeAssembly reqAssembly, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks) +232
System.Reflection.RuntimeAssembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean forIntrospection) +113
System.Reflection.RuntimeAssembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection) +23
System.Reflection.Assembly.Load(String assemblyString) +35
System.Web.Configuration.CompilationSection.LoadAssemblyHelper(String assemblyName, Boolean starDirective) +48

[ConfigurationErrorsException: Could not load file or assembly 'Microsoft.CSharp, Version=8.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.]
System.Web.Configuration.CompilationSection.LoadAssemblyHelper(String assemblyName, Boolean starDirective) +767
System.Web.Configuration.CompilationSection.LoadAssembly(AssemblyInfo ai) +85
System.Web.Compilation.BuildManager.GetReferencedAssemblies(CompilationSection compConfig) +287
System.Web.Compilation.BuildManager.GetPreStartInitMethodsFromReferencedAssemblies() +69
System.Web.Compilation.BuildManager.CallPreStartInitMethods(String preStartInitListPath, Boolean& isRefAssemblyLoaded) +137
System.Web.Compilation.BuildManager.ExecutePreAppStart() +172
System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters, PolicyLevel policyLevel, Exception appDomainCreationException) +854

[HttpException (0x80004005): Could not load file or assembly 'Microsoft.CSharp, Version=8.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.]
System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +532
System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +111
System.Web.HttpRuntime.ProcessRequestNotificationPrivate(IIS7WorkerRequest wr, HttpContext context) +719| | -------- | |[FileNotFoundException: Could not load file or assembly 'Microsoft.CSharp, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.] [FileNotFoundException: Could not load file or assembly 'Microsoft.CSharp, Version=8.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.] System.Reflection.RuntimeAssembly._nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, RuntimeAssembly locationHint, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks) +0 System.Reflection.RuntimeAssembly.InternalLoadAssemblyName(AssemblyName assemblyRef, Evidence assemblySecurity, RuntimeAssembly reqAssembly, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks) +232 System.Reflection.RuntimeAssembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean forIntrospection) +113 System.Reflection.RuntimeAssembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection) +23 System.Reflection.Assembly.Load(String assemblyString) +35 System.Web.Configuration.CompilationSection.LoadAssemblyHelper(String assemblyName, Boolean starDirective) +48 [ConfigurationErrorsException: Could not load file or assembly 'Microsoft.CSharp, Version=8.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.] System.Web.Configuration.CompilationSection.LoadAssemblyHelper(String assemblyName, Boolean starDirective) +767 System.Web.Configuration.CompilationSection.LoadAssembly(AssemblyInfo ai) +85 System.Web.Compilation.BuildManager.GetReferencedAssemblies(CompilationSection compConfig) +287 System.Web.Compilation.BuildManager.GetPreStartInitMethodsFromReferencedAssemblies() +69 System.Web.Compilation.BuildManager.CallPreStartInitMethods(String preStartInitListPath, Boolean& isRefAssemblyLoaded) +137 System.Web.Compilation.BuildManager.ExecutePreAppStart() +172 System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters, PolicyLevel policyLevel, Exception appDomainCreationException) +854 [HttpException (0x80004005): Could not load file or assembly 'Microsoft.CSharp, Version=8.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.] System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +532 System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +111 System.Web.HttpRuntime.ProcessRequestNotificationPrivate(IIS7WorkerRequest wr, HttpContext context) +719|

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Answer 1

Hi @Simon,

I'm afraid I can't locate the cause of the problem or reproduce the problem based on the error message alone. You can try the following methods and check if this work for you:

1. Start Visual Studio as an administrator and run the project
2. Delete the bin and obj files in the project directory and rebuild the project.
3. Create a new project and install the same assembly and check if the same issue occurs.

|[FileNotFoundException: Could not load file or assembly 'Microsoft.CSharp, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.] [FileNotFoundException: Could not load file or assembly 'Microsoft.CSharp, Version=8.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.]

And from the stack information, it can be seen that your program is trying to load two different versions of the CSharp assembly. It looks like your project has both of them installed. Please check it, this should be the cause of the problem.

Best regards,

Xudong Peng

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