I was getting the same and resolved this issue by following these steps.
C:\Windows\Microsoft.NET\assembly\GAC_MSIL\NuGet.Core\v4.0_1.6.30117.9648__31bf3856ad364e35\NuGet.Core.dll
or
B. Check is available in BIN folder of your application or not.
....\BIN\NuGet.Core.dll
If not you may download from http://docs.nuget.org/consume/installing-nuget
Install and you will find NuGet.Core.dll.
Now placed in any of the mentioned location.
Core Error:
Server Error in '/' Application.
Could not load file or assembly 'NuGet.Core, Version=1.6.30117.9648, Culture=neutral, PublicKeyToken=31bf3856ad364e35' 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 'NuGet.Core, Version=1.6.30117.9648, Culture=neutral, PublicKeyToken=31bf3856ad364e35' 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.
Stack Trace:
[FileNotFoundException: Could not load file or assembly 'NuGet.Core, Version=1.6.30117.9648, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.]
System.Reflection.RuntimeAssembly.GetExportedTypes(RuntimeAssembly assembly, ObjectHandleOnStack retTypes) +0
System.Reflection.RuntimeAssembly.GetExportedTypes() +21
System.Web.WebPages.ApplicationParts.ResourceAssembly.GetTypes() +13
System.Web.WebPages.ApplicationParts.ApplicationPartRegistry.Register(ApplicationPart applicationPart, Func`1 registerPageAction) +116
System.Web.WebPages.ApplicationPart.Register(ApplicationPart applicationPart) +51
System.Web.WebPages.Administration.SiteAdmin.RegisterAdminModule() +110
System.Web.WebPages.Administration.PreApplicationStartCode.Start() +28
[TargetInvocationException: Exception has been thrown by the target of an invocation.]
System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor) +0
System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Object[] arguments) +192
System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture) +155
System.Web.WebPages.Deployment.PreApplicationStartCode.LoadWebPages(Version version) +238
System.Web.WebPages.Deployment.PreApplicationStartCode.StartCore(IFileSystem fileSystem, String appDomainAppPath, String binDirectory, NameValueCollection appSettings, IEnumerable`1 loadedAssemblies, IBuildManager buildManager, Action`1 loadWebPages, Action registerForChangeNotification, Func`2 getAssemblyNameThunk) +256
System.Web.WebPages.Deployment.PreApplicationStartCode.StartCore() +167
System.Web.WebPages.Deployment.PreApplicationStartCode.Start() +33
[InvalidOperationException: The pre-application start initialization method Start on type System.Web.WebPages.Deployment.PreApplicationStartCode threw an exception with the following error message: Exception has been thrown by the target of an invocation..]
System.Web.Compilation.BuildManager.InvokePreStartInitMethodsCore(ICollection`1 methods, Func`1 setHostingEnvironmentCultures) +547
System.Web.Compilation.BuildManager.InvokePreStartInitMethods(ICollection`1 methods) +132
System.Web.Compilation.BuildManager.CallPreStartInitMethods(String preStartInitListPath, Boolean& isRefAssemblyLoaded) +102
System.Web.Compilation.BuildManager.ExecutePreAppStart() +153
System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters, PolicyLevel policyLevel, Exception appDomainCreationException) +521
[HttpException (0x80004005): The pre-application start initialization method Start on type System.Web.WebPages.Deployment.PreApplicationStartCode threw an exception with the following error message: Exception has been thrown by the target of an invocation..]
System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +9930568
System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +101
System.Web.HttpRuntime.ProcessRequestNotificationPrivate(IIS7WorkerRequest wr, HttpContext context) +254
Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.34209
Solution:
A. Check is available in GAC or not.C:\Windows\Microsoft.NET\assembly\GAC_MSIL\NuGet.Core\v4.0_1.6.30117.9648__31bf3856ad364e35\NuGet.Core.dll
or
B. Check is available in BIN folder of your application or not.
....\BIN\NuGet.Core.dll
If not you may download from http://docs.nuget.org/consume/installing-nuget
Install and you will find NuGet.Core.dll.
Now placed in any of the mentioned location.
Core Error:
Server Error in '/' Application.
Could not load file or assembly 'NuGet.Core, Version=1.6.30117.9648, Culture=neutral, PublicKeyToken=31bf3856ad364e35' 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 'NuGet.Core, Version=1.6.30117.9648, Culture=neutral, PublicKeyToken=31bf3856ad364e35' 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.
Stack Trace:
[FileNotFoundException: Could not load file or assembly 'NuGet.Core, Version=1.6.30117.9648, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.]
System.Reflection.RuntimeAssembly.GetExportedTypes(RuntimeAssembly assembly, ObjectHandleOnStack retTypes) +0
System.Reflection.RuntimeAssembly.GetExportedTypes() +21
System.Web.WebPages.ApplicationParts.ResourceAssembly.GetTypes() +13
System.Web.WebPages.ApplicationParts.ApplicationPartRegistry.Register(ApplicationPart applicationPart, Func`1 registerPageAction) +116
System.Web.WebPages.ApplicationPart.Register(ApplicationPart applicationPart) +51
System.Web.WebPages.Administration.SiteAdmin.RegisterAdminModule() +110
System.Web.WebPages.Administration.PreApplicationStartCode.Start() +28
[TargetInvocationException: Exception has been thrown by the target of an invocation.]
System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor) +0
System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Object[] arguments) +192
System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture) +155
System.Web.WebPages.Deployment.PreApplicationStartCode.LoadWebPages(Version version) +238
System.Web.WebPages.Deployment.PreApplicationStartCode.StartCore(IFileSystem fileSystem, String appDomainAppPath, String binDirectory, NameValueCollection appSettings, IEnumerable`1 loadedAssemblies, IBuildManager buildManager, Action`1 loadWebPages, Action registerForChangeNotification, Func`2 getAssemblyNameThunk) +256
System.Web.WebPages.Deployment.PreApplicationStartCode.StartCore() +167
System.Web.WebPages.Deployment.PreApplicationStartCode.Start() +33
[InvalidOperationException: The pre-application start initialization method Start on type System.Web.WebPages.Deployment.PreApplicationStartCode threw an exception with the following error message: Exception has been thrown by the target of an invocation..]
System.Web.Compilation.BuildManager.InvokePreStartInitMethodsCore(ICollection`1 methods, Func`1 setHostingEnvironmentCultures) +547
System.Web.Compilation.BuildManager.InvokePreStartInitMethods(ICollection`1 methods) +132
System.Web.Compilation.BuildManager.CallPreStartInitMethods(String preStartInitListPath, Boolean& isRefAssemblyLoaded) +102
System.Web.Compilation.BuildManager.ExecutePreAppStart() +153
System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters, PolicyLevel policyLevel, Exception appDomainCreationException) +521
[HttpException (0x80004005): The pre-application start initialization method Start on type System.Web.WebPages.Deployment.PreApplicationStartCode threw an exception with the following error message: Exception has been thrown by the target of an invocation..]
System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +9930568
System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +101
System.Web.HttpRuntime.ProcessRequestNotificationPrivate(IIS7WorkerRequest wr, HttpContext context) +254
Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.34209