Could not load file or assembly 'Microsoft.Practices.EnterpriseLibrary.Common, Version=6.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or

I tried to use Logging in Enterprise Library 6.0 in VS2015 and the following exception pops up. The reference Microsoft.Practices.EnterpriseLibray.Common is already added in the references of VS2015.

Server Error in '/' Application.

Could not load file or assembly 'Microsoft.Practices.EnterpriseLibrary.Common, Version=6.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040) 
  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.FileLoadException: Could not load file or assembly 'Microsoft.Practices.EnterpriseLibrary.Common, Version=6.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

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.  

Assembly Load Trace: The following information can be helpful to determine why the assembly 'Microsoft.Practices.EnterpriseLibrary.Common, Version=6.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' could not be loaded.



=== Pre-bind state information ===
LOG: DisplayName = Microsoft.Practices.EnterpriseLibrary.Common, Version=6.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35
 (Fully-specified)
LOG: Appbase = file:///c:/users/damarat/documents/visual studio 2015/Projects/LoginForm/LoginForm/
LOG: Initial PrivatePath = c:\users\damarat\documents\visual studio 2015\Projects\LoginForm\LoginForm\bin
Calling assembly : Microsoft.Practices.EnterpriseLibrary.Configuration.DesignTime, Version=6.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35.
===
LOG: This bind starts in default load context.
LOG: Using application configuration file: c:\users\damarat\documents\visual studio 2015\Projects\LoginForm\LoginForm\web.config
LOG: Using host configuration file: C:\Users\damarat\Documents\IISExpress\config\aspnet.config
LOG: Using machine configuration file from C:\Windows\Microsoft.NET\Framework\v4.0.30319\config\machine.config.
LOG: Redirect found in application configuration file: 6.0.0.0 redirected to 6.0.0.0.
LOG: Post-policy reference: Microsoft.Practices.EnterpriseLibrary.Common, Version=6.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35
LOG: Attempting download of new URL file:///C:/Windows/Microsoft.NET/Framework/v4.0.30319/Temporary ASP.NET Files/root/b1f5e761/8f0d1b40/Microsoft.Practices.EnterpriseLibrary.Common.DLL.
LOG: Attempting download of new URL file:///C:/Windows/Microsoft.NET/Framework/v4.0.30319/Temporary ASP.NET Files/root/b1f5e761/8f0d1b40/Microsoft.Practices.EnterpriseLibrary.Common/Microsoft.Practices.EnterpriseLibrary.Common.DLL.
LOG: Attempting download of new URL file:///c:/users/damarat/documents/visual studio 2015/Projects/LoginForm/LoginForm/bin/Microsoft.Practices.EnterpriseLibrary.Common.DLL.
WRN: Comparing the assembly name resulted in the mismatch: Major Version
ERR: Failed to complete setup of assembly (hr = 0x80131040). Probing terminated.



Stack Trace: 



[FileLoadException: Could not load file or assembly 'Microsoft.Practices.EnterpriseLibrary.Common, Version=6.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)]
   System.ModuleHandle.ResolveType(RuntimeModule module, Int32 typeToken, IntPtr* typeInstArgs, Int32 typeInstCount, IntPtr* methodInstArgs, Int32 methodInstCount, ObjectHandleOnStack type) +0
   System.ModuleHandle.ResolveTypeHandleInternal(RuntimeModule module, Int32 typeToken, RuntimeTypeHandle[] typeInstantiationContext, RuntimeTypeHandle[] methodInstantiationContext) +145
   System.Reflection.RuntimeModule.ResolveType(Int32 metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments) +158
   System.Reflection.CustomAttribute.FilterCustomAttributeRecord(CustomAttributeRecord caRecord, MetadataImport scope, Assembly& lastAptcaOkAssembly, RuntimeModule decoratedModule, MetadataToken decoratedToken, RuntimeType attributeFilterType, Boolean mustBeInheritable, Object[] attributes, IList derivedAttributes, RuntimeType& attributeType, IRuntimeMethodInfo& ctor, Boolean& ctorHasParameters, Boolean& isVarArg) +91
   System.Reflection.CustomAttribute.GetCustomAttributes(RuntimeModule decoratedModule, Int32 decoratedMetadataToken, Int32 pcaCount, RuntimeType attributeFilterType, Boolean mustBeInheritable, IList derivedAttributes, Boolean isDecoratedTargetSecurityTransparent) +438
   System.Reflection.CustomAttribute.GetCustomAttributes(RuntimeAssembly assembly, RuntimeType caType) +103
   System.Reflection.RuntimeAssembly.GetCustomAttributes(Boolean inherit) +37
   Owin.Loader.DefaultLoader.SearchForStartupAttribute(String friendlyName, IList`1 errors, Boolean& conflict) +106
   Owin.Loader.DefaultLoader.GetDefaultConfiguration(String friendlyName, IList`1 errors) +46
   Owin.Loader.DefaultLoader.LoadImplementation(String startupName, IList`1 errorDetails) +75
   Owin.Loader.DefaultLoader.Load(String startupName, IList`1 errorDetails) +21
   Microsoft.Owin.Host.SystemWeb.OwinBuilder.GetAppStartup() +115
   Microsoft.Owin.Host.SystemWeb.OwinHttpModule.InitializeBlueprint() +28
   System.Threading.LazyInitializer.EnsureInitializedCore(T& target, Boolean& initialized, Object& syncLock, Func`1 valueFactory) +115
   Microsoft.Owin.Host.SystemWeb.OwinHttpModule.Init(HttpApplication context) +106
   System.Web.HttpApplication.RegisterEventSubscriptionsWithIIS(IntPtr appContext, HttpContext context, MethodInfo[] handlers) +534
   System.Web.HttpApplication.InitSpecial(HttpApplicationState state, MethodInfo[] handlers, IntPtr appContext, HttpContext context) +172
   System.Web.HttpApplicationFactory.GetSpecialApplicationInstance(IntPtr appContext, HttpContext context) +352
   System.Web.Hosting.PipelineRuntime.InitializeApplication(IntPtr appContext) +296

[HttpException (0x80004005): Could not load file or assembly 'Microsoft.Practices.EnterpriseLibrary.Common, Version=6.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)]
   System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +9947444
   System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +101
   System.Web.HttpRuntime.ProcessRequestNotificationPrivate(IIS7WorkerRequest wr, HttpContext context) +261




Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.6.1055.0  

Help me out to figure it out

The DLL that you are referring might be a different version or might be not referenced at all.

1. Try removing and re-adding the reference.
2. Try setting the Version Specific to false in the properties.