void IExtensionConfigProvider.Initialize(ExtensionConfigContext context) { if (context == null) { throw new ArgumentNullException(nameof(context)); } var keyVaultService = new KeyVaultService(); Func <KeyVaultAttribute, CancellationToken, Task <string> > builder = (KeyVaultAttribute keyVaultAttribute, CancellationToken cancellationToken) => { return(keyVaultService.GetValueAsync(keyVaultAttribute, cancellationToken)); }; context .AddBindingRule <KeyVaultAttribute>() .BindToInput(builder) ; }