Disabling Column in Entity Framework Code First

Question

I'm using Entity Framework to insert data into 2 different databases. There are a few columns that are present in one of the databases but not the other. Their data types are not nullable (int and float).

I don't use these columns (when they are present) in my code. Meaning I only insert 0 as the data for them but I can't send null obviously.

Is there a way for me to insert data with ease without creating 2 different versions of my app for these? Ideally I'd like to just have one model with something like an attribute that says insert 0 in this column if it's available.

David Browne - Microsoft · Accepted Answer · 2018-10-09 17:08:41Z

1

If your application runs only against one database, then you can just use an IF statement in your OnModelCreating that uses the Fluent API to .Ignore() the missing properties.

public class MyDbContextWithMissingColumns: MyDbContext
{
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        if (myConfig.UseDatabaseWithoutSomeProperties)
        {
          modelBuilder.Entity<Foo>().Ignore(f => f.SomeProperty);
        }
        base.OnModelCreating(modelBuilder);
    }
}

If a single instance of your application connects to both databases, then you have to use separate DbContext subtype, as OnModelCreating only runs for the first instance of a DbContext type in an AppDomain.

EG:

public class MyDbContextWithMissingColumns: MyDbContext
{
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Foo>().Ignore(f => f.SomeProperty);
        base.OnModelCreating(modelBuilder);
    }
}

edited Oct 9, 2018 at 17:08

answered Oct 7, 2018 at 15:36

David Browne - Microsoft

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2 Comments

Alireza Noori Over a year ago

This seems to be exactly what I'm looking for. However it seems that my best option is to have an if statement to use the Ignore() whenever I'm using the 2nd database.

David Browne - Microsoft Over a year ago

If you never have a single instance of your application that connects to both databases, then an IF statement in OnModelCreating will work. But OnModelCreating only runs for the first instance of a DbContext type in an AppDomain. See updated answer.

Peter Smith · Accepted Answer · 2018-10-07 15:47:23Z

0

In the repository for the database with the restricted fields create the entity:

public class MyClass
{
   int MyCommonClassID {get; set;}
   string Name {get; set;}
   [NotMapped]
   string PhoneNumber {get; set;}
}

Where the attribute [NotMapped]. is used that field will not appear in the database but you can use it everywhere else. That wat you determine what gets written at the lowest level and your application doesn't care.

answered Oct 7, 2018 at 15:47

Peter Smith

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