Code-First Development with Entity Framework 4
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by Scott Guthrie
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Adding a new Property to the Dinner Model

Let’s walkthrough making a simple change to our Dinner class.  Specifically, we’ll add an additional property to our Dinner class called “Country”:

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Now that we’ve made this change, let’s press F5 in Visual Studio to build and re-run the application.  When we do this we’ll see the below error message:

image

This error message occurs because we’ve changed the structure of our Dinner class, and our model object is now no longer the same shape as the “Dinners” table we automatically created within our database. 

When EF automatically creates a database for you, it by default adds an “EdmMetadata” table to the database that tracks the shape of the model objects that were used to automatically create the database schema for you: 

image

The error message above occurs when EF detects that you’ve made a change to a model object and it is now out of sync with the database it automatically created for you. 


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