ef core There is already an open DataReader associated with this Command which must be closed first. code example

Example: There is already an open DataReader associated with this Command which must be closed first c#

<connectionStrings>
    <add name="IdentityConnection" connectionString="Data Source=(LocalDb)\v11.0;AttachDbFilename=|DataDirectory|\IdentityDb.mdf;Integrated Security=True;MultipleActiveResultSets=true;" providerName="System.Data.SqlClient" />
  </connectionStrings>