CodeFirst

Easiest way to debug Seed-method in EF Code-first migrations in Configuration.cs when running Update-Database

Sequence contains more than one element

This post describes the easiest way to debug the issues that may stop your Seed-method in Configuration.cs from going through. The solution here shows you, how you can get a little bit more information out of the process, without attaching the debugger (there’s another blog post for that!)

Description

Entity Framework’s code-first migration’s are a beautiful and easy way of managing database schema changes and populating some preliminary data there. Personally I also sometimes use the method for adding some enrichment to data or or custom property values mapping that would otherwise require an additional/external console program.

Problem: running the Seed-method is by default undebuggable

Okay – so seeding data is cool. That’s fine and dandy, but debugging the issues in the function while running Update-Database is NOT so cool. You only get the stacktrace and exception message – and that’s pretty ugly.

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Applying Entity Framework’s Code-First Migrations against a Database in Azure by running Update-Database

This post describes how to run Entity Framework’s code-first migrations against a database located in the Windows Azure. This is done by running Update-Database commandlet with suitable switches, see below.

The problem and symptoms

Okay, so you’re developing your MVC+EF cool web app with a database in Azure, and you’re using code-first migrations. Cool! What’s nice with code-first-migrations is the fact they are run automatically even in the cloud the next time your app is running (as long as you publish your app with that little box ticked – something like in the screen capture below). But wait – what if there are conflicts – what kind of errors are you going to get?

 

Azure Web Publish

Azure Web Publish

Not very useful ones, I’m afraid, and it’s a pain navigating the Azure portal to fetch the log files. At some point – for me, it wasn’t the first time I ran the web app, but the phase when I was logging in – you’ll be getting the error the migrator internally throws. That might be enough to point you to the right direction, and maybe you’ll be able to figure out what’s wrong! But if that’s not the case, here’s the way to run Update-Database against your Azure Database!

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Fixing the error: “Column XX in table dbo.YY is of a type that is invalid for use as a key column in an index.”

entity-framework-logo

While using Entity Framework and code-first migrations, Entity Framework (EF) creates the indexes for you – but what if you need to create a custom one, explicitly based on certain field / column? Then you’ll have to tell EF which one to use as a key column. Usually, it’s easy – you just add the following annotation to the columns you’ll be using:

(example stripped of extra code and other columns for clarity)

And after adding the migration (Add-Migration… commandlet) you get something like this:

But what if, when running Update-Database, you get an error like:

There’s a quick and simple solution.

Solution

This exception comes from the fact that indexes in EF have the maximum length of 900 chars. If you are like me, you’ll have been a little lazy and you have created your string-typed model variables without specifying a maximum length for them, and this causes the length of the index values to be way too long.

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Fixing “An error occurred while updating the entries” while running code-first migrations in MVC 5 app

Update-Database error

This post describes an issue with EF’s code-first migrations, when mapping between DB’s DateTime and C#’s DateTime kind of fails, and results in Update-Database cmdlet failing. It’s more or less a prime example of a situation, where the error itself tells very little about the actual issue, and since debugging code-first migrations is kind of difficult (see the best tips for that here!), it’s cumbersome to investigate.

Symptoms

While running Update-Database in a code-first ASP.NET MVC5 + EF6 -project, you get a following (or similar) error:

An error occurred while updating the entries. See the inner exception for details.

The whole, pretty terrifying error message is the following:

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