c# - An exception of type 'System.Configuration.ConfigurationErrorsException' occurred in System.Data.dll but was not handled in user code -

i developing asp.net mvc application mysql. running smoothly until got error after building web project: an exception of type 'system.configuration.configurationerrorsexception' occurred in system.data.dll not handled in user code

here exception details:

system.configuration.configurationerrorsexception unhandled user code   hresult=-2146232062   message=Échec de la recherche ou du chargement du fournisseur de données .net framework inscrit.   source=system.data   baremessage=Échec de la recherche ou du chargement du fournisseur de données .net framework inscrit.   line=0   stacktrace:        à system.data.common.dbproviderfactories.getfactory(datarow providerrow)        à system.data.common.dbproviderfactories.getfactory(string providerinvariantname)        à system.data.entityclient.entityconnection.getfactory(string providerstring)        à system.data.entityclient.entityconnection.changeconnectionstring(string newconnectionstring)        à system.data.entityclient.entityconnection..ctor(string connectionstring)        à system.data.entity.internal.lazyinternalconnection.initializefromconnectionstringsetting(connectionstringsettings appconfigconnection)        à system.data.entity.internal.lazyinternalconnection.tryinitializefromappconfig(string name, appconfig config)        à system.data.entity.internal.lazyinternalconnection.initialize()        à system.data.entity.internal.lazyinternalconnection.createobjectcontextfromconnectionmodel()        à system.data.entity.internal.lazyinternalcontext.initializecontext()        à system.data.entity.internal.internalcontext.initialize()        à system.data.entity.internal.internalcontext.getentitysetandbasetypefortype(type entitytype)        à system.data.entity.internal.linq.internalset`1.initialize()        à system.data.entity.internal.linq.internalset`1.getenumerator()        à system.data.entity.infrastructure.dbquery`1.system.collections.generic.ienumerable<tresult>.getenumerator()        à system.collections.generic.list`1..ctor(ienumerable`1 collection)        à system.linq.enumerable.tolist[tsource](ienumerable`1 source)        à thechef.data.infrastructure.repositorybase`1.getall() dans c:\users\segour junior 1\documents\visual studio 2013\projects\thechef-rms\thechef.data\infrastructure\repositorybase.cs:ligne 72        à thechef.service.employeservice.retrieveall() dans c:\users\segour junior 1\documents\visual studio 2013\projects\thechef-rms\thechef.service\personnel\employeservice.cs:ligne 34        à thechef.web.controlleractionshandlers.employeactionshandler.list() dans c:\users\segour junior 1\documents\visual studio 2013\projects\thechef-rms\thechef.web\controlleractionshandlers\personnel\employeactionshandler.cs:ligne 57        à thechef.web.controllers.employecontroller.index() dans c:\users\segour junior 1\documents\visual studio 2013\projects\thechef-rms\thechef.web\controllers\personnel\employecontroller.cs:ligne 50        à lambda_method(closure , controllerbase , object[] )        à system.web.mvc.actionmethoddispatcher.execute(controllerbase controller, object[] parameters)        à system.web.mvc.reflectedactiondescriptor.execute(controllercontext controllercontext, idictionary`2 parameters)        à system.web.mvc.controlleractioninvoker.invokeactionmethod(controllercontext controllercontext, actiondescriptor actiondescriptor, idictionary`2 parameters)        à system.web.mvc.async.asynccontrolleractioninvoker.actioninvocation.invokesynchronousactionmethod()        à system.web.mvc.async.asynccontrolleractioninvoker.<begininvokesynchronousactionmethod>b__39(iasyncresult asyncresult, actioninvocation innerinvokestate)        à system.web.mvc.async.asyncresultwrapper.wrappedasyncresult`2.callenddelegate(iasyncresult asyncresult)        à system.web.mvc.async.asyncresultwrapper.wrappedasyncresultbase`1.end()        à system.web.mvc.async.asyncresultwrapper.end[tresult](iasyncresult asyncresult, object tag)        à system.web.mvc.async.asynccontrolleractioninvoker.endinvokeactionmethod(iasyncresult asyncresult)        à system.web.mvc.async.asynccontrolleractioninvoker.asyncinvocationwithfilters.<invokeactionmethodfilterasynchronouslyrecursive>b__3d()        à system.web.mvc.async.asynccontrolleractioninvoker.asyncinvocationwithfilters.<>c__displayclass46.<invokeactionmethodfilterasynchronouslyrecursive>b__3f()   innerexception:  

my application architecture follows of asp.net mvc solution architecture – best practices christos s. on february 15, 2015 give idea of how solution structured. when launch debugging, execution stops @ line in repositorybase.cs file:

public virtual ienumerable<t> getall() {     return dbset.tolist(); } 

what have done far solve issue:

1. check configuration files, app.config in model project have ado entity data model file , web.config in web project see if has changed.
2. uninstall visual studio , related .net framework installations , reinstall visual studio.
3. google error and/or additional information provided on yellow page. found stackoverflow.com related questions such configurationerrorexception in trying run console app mysql entity framework 6 , c# - compiler error: system.configuration.configurationerrorsexception unhandled didn't much.

one more point: error occurs when open view retrieves data database.

please !