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.”

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While using Entity Framework and code-first migrations, EF creates the indexes for you – but what if you need to create a custom one? 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…) you get something like this:

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

There’s a quick and simple solution.

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