Tag Archives: .NET

Unable to Migrate after Adding Config to Startup

Hi everyone,

Just a quick post on fixing up a migration error after I added new config to startup.cs via DI. The error after running add-migration was pretty unintuitive:

Unable to create an object of type 'ApplicationDbContext'. For the different patterns supported at design time, see https://go.microsoft.com/fwlink/?linkid=851728

To find out a bit more I ran the following:

add-migration -verbose

This revealed the fact that there was an issue with adding my config line. The error stated that I had to have an empty constructor which led me on a bit of a wild goose chase.

The solution was simply a missed entry in application.json. In my case it was an omitted “assembly” section. Having said that, I did come across a few instances where people had the same problem when omitting commas etc.

Hopefully that’s able to get you on the right track!

Thanks,
Chris

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Unable to Access RDS Database from Elastic Beanstalk Application

Hey everyone,

I ran into a bit of an issue today where I was unable to access my RDS SQL Express instance from my .NET Elastic Beanstalk instance. I was receiving the following error:

The server was not found or was not accessible.

The solution turned out to be fairly simply thanks to this StackOverflow post: http://stackoverflow.com/a/33207022/522859

Get your server instance security group:
– Log into AWS
– Navigate to elastic beanstalk
– Open your application instance
– Open configuration
– Open instances
– Find “server” on the page and copy the value in the “EC2 security groups” field

Add your server instance security group to your rds rules:
– Navigate to the RDS Dashboard
– Open your RDS instance
– Click on view details (left hand side or top)
– Find Security and Network
– Click on the rds-launch-wizard under security groups
– Click on inbound rules (very bottom currently)
– Add a new inbound rule with the copied security group as the source