PasswordCredentials.Password在PasswordVault中始终为空

Muh*_*lah 2 winrt-xaml windows-phone-8.1 win-universal-app

我正在尝试按照代码在Windows Phone 8.1中存储用户名密码.密码保存它存储数据但当我检索回密码字段时总是为空.

  PasswordVault passwordVault = new PasswordVault();
  passwordVault.Add(new PasswordCredential("MyResouceKey", "username", "Password"));

 // Retrieval
 var credential = passwordVault.FindAllByResource("MyResourceKey");
  return credential.Password; /// it is always empty.
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密码始终为空