c# - Key store providers cannot be set more than once (Always Encryption using Azure Function ) -

i've implemented timetriggerc# azure function run store procedure insert table encrypted using column encryption(always encrypted, azurekey vault provider)

the blocking area me function ran @ 1 time , got error again many times. success path rare case

the error faced

mscorlib: exception has been thrown target of invocation. system.data: key store providers cannot set more once.

i done investigation on occurs in line

sqlconnection.registercolumnencryptionkeystoreproviders(providers); 

with in function

static void initializeazurekeyvaultprovider() {     string clientid = configurationmanager.appsettings["authclientid"];     string clientsecret = configurationmanager.appsettings["authclientsecret"];     _clientcredential = new clientcredential(clientid, clientsecret);      // direct provider authentication delegate     sqlcolumnencryptionazurekeyvaultprovider azurekeyvaultprovider = new sqlcolumnencryptionazurekeyvaultprovider(gettoken);      dictionary<string, sqlcolumnencryptionkeystoreprovider> providers = new dictionary<string, sqlcolumnencryptionkeystoreprovider>();     providers.add(sqlcolumnencryptionazurekeyvaultprovider.providername, azurekeyvaultprovider);      // register provider ado.net     sqlconnection.registercolumnencryptionkeystoreproviders(providers); } 

when tried deeper root cause of error, like

exception has been thrown target of invocation. ---> system.invalidoperationexception : key store providers cannot set more once. @ system.data.sqlclient.sqlconnection.registercolumnencryptionkeystoreproviders(idictionary`2 customproviders)

as mentioned above used azure key vault key store provider.i registered keyvault ad , added registered application key vault (access policies).

why i'm facing abnormal behavior, one-time success , time failure?

appreciate response,
jayendran

you running initializeazurekeyvaultprovider() inside every function call. if works first time, when initialization wasn't performed on app instance.

during next function call instance gets reused, initialization performed. call again, duplicated registration error.

to solve it, initialization in static constructor, or store flag (static bool) whether initialized already, , skip initialization if it's true (and take care of thread safety).