Making Complex Types Useful with Entity Framework 6 Custom Configurations -- Visual Studio Magazine
This paper presents a quality-entity-relationship (QER) approach for incorporating quality research, we adopt the following naming convention for the following entity-relationship constructs: attribute lower case, hyphenate words . "attribute name" double quote to denote the name of an attribute ) Orlando, Florida. Explain entity-relationship (ER) model and identify its building blocks: Entity Apply rules for mapping E-R models to the relational model. . CarParts Mariposa Orlando FL Differentiate between attribute name and attribute value. In this column, I'll work through this problem using Entity Framework Code First Conventions. . objects, I need to set the name attribute on each tag in the table to the name of the class Orlando, FL; Visual Studio Live!.
A recent project I worked on had multiple service technicians assigned to multiple locations, for instance. It's also not unusual for there to be data that applies only to the relationship.
Data Modelling with UML
In my client's project, for example, at any location, a service technician has a specific position -- and that position can be different from one location to another. For instance, at one location, the tech might be the "responsible authority"; at another location, the tech might be the "support technician. By the end of the column you'll have a roadmap for handling many-to-many relationships in your applications.
My first step was to create the class that defines the many-to-many relationship between techs and locations the Location, Job and ServiceTech classes were already defined: Finally, the class gives the TechsLocation entity a property to hold the phone extension number Ext for the tech at that location.
With all the entities defined, the next step is to add them to the DataContext: HasMany Function t t.
WithRequired Function tl tl. HasForeignKey Function tl tl. TechId I also need to do the same thing on the Location side of the relationship: HasMany Function l l.
Modeling Quality Requirements
That's easier to define: HasRequired Function tl tl. Map Sub tl tl.
I do, however, need to set the other properties Location, extension and Job for TechsLocations: SaveChanges Deleting a Tech now requires two steps: The code to delete the Tech I just created looks like this: Remove tl Next dc. Remove tch Updating requires more complex code because, before doing any updates, I want to check to see if the tech's assignments have been changed.
CompareTo If TextId - other. In that case, I throw away all the tech's current TechsLocations, create new ones from the selected TechsLocationsDTOs collection I received earlier, add the new TechsLocations objects to my tech object, and eventually save the changes to the database, as shown in Listing 2.Entity, Entity Type, Entity Set - Database Management System
SequenceEqual tchTls Then tch. Single Function j j. Add tchLcn Next End If dc.
To prevent that, you should add a constructor to your entity class holding the Complex Type and initialize the properties that use the Complex Type. For my Customer class, that code would look like this: That is, until the EF6 custom conventions and configurations come along to give you more control over how your EF model ties to your database.
You just need a little bit of fluent code in your DbContext OnModelCreating method to resolve this problem. The first step is to pick the class your convention will apply to, using the ModelBuilder Types collection.
In my example, I want to control my Customer entity class, so I specify it in the Types collection: The Configure method accepts a lambda expression and passes that expression a ConventionTypeConfiguration object.
I want to override the configuration for one of my entity's properties, so I use the Property method on the ConventionTypeConfiguration object: The Property method also accepts a lambda expression that allows you to specify which property on the entity you want to configure this lambda expression is passed the entity's description.
Finally, you supply the configuration for the property. Once I've got the objects I want, I can do what's necessary to tie those well-designed entity objects to my database. And that's the right thing to do.