.NET Core System.InvalidOperationException：实例失败

Question

When connecting EF Core to a local SQL Express instance I'm suddenly seeing the following error -

System.InvalidOperationException: Instance failure.
   at Microsoft.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection)...

The connection string is coming from my appsettings.json file -

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft": "Warning",
      "Microsoft.Hosting.Lifetime": "Information"
    }
  },
  "ConnectionStrings:DefaultDatabase": "Server=.\\SQLEXPRESS;Database=MyDatabase;Trusted_Connection=True;User ID=sqluser;Password=password;"
}

I'm accessing the configuration like so -

public void InitializeContainer(IServiceCollection services, IConfiguration configuration)
{
    var db = configuration.GetValue<string>("ConnectionStrings:ConnectionStrings:DefaultDatabase");

    services.AddDbContext<MyContext>(options =>
        options.UseSqlServer(db));
}

I know the reason I'm seeing this error is because the string is being escaped, so my variable ends up looking like this Server=.\\\\SQLEXPRESS;Database=CustomerContact;Trusted_Connection=True;User ID=swwdev;Password=password; .

Fine, but how do I get around this? If I change appsettings.json to a single \ I get another error saying the JSON is invalid. I can't understand what has changed as it was working up until recently.

Answer 1

Both the appsettings.json file and the configuration code have problems.

Change your connection string section to this:

"ConnectionStrings": {
      "DefaultConnection": "Data Source=localhost;Initial Catalog=MyDatabase;Integrated Security=False;User ID=...;Password=...;Connect Timeout=15;Encrypt=False;Packet Size=4096;"
}
....

and your startup file:

public IConfiguration Configuration { get; }

        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

.....
var connString=Configuration.GetConnectionString("DefaultConnection");
services.AddDbContext<MyContext>(options => options.UseSqlServer(connString));