EF 6 Codefirst -Setting default value for a property defined in base class using fluent API

问题

I have a base class which has audit properties like

public abstract class BaseModel
{
    [Column(Order = 1)] 
    public long Id { get; set; }
    public long CreatedBy { get; set; }
    public DateTime CreatedDate { get; set; }
    public long ModifiedBy { get; set; }
    public DateTime ModifiedDate { get; set; }
    public bool IsActive { get; set; }
}

All my poco classes derive from this class.

I am trying to set a default value to the IsActive properties. I am not keen on using annotations and hence was wandering if I can work this using fluent API.

I tried this but it does not work. Seems like it creates a new table named BaseModel

modelBuilder.Entity<BaseModel>()
    .Property(p => p.IsActive)
    .HasColumnAnnotation("DefaultValue", true);

Can any one suggest a way here?

回答1:

There is no way to do this. It can't set default values with Entity Framework. Instead you can use the constructor

public abstract class BaseModel
{
    protected BaseModel()
    {
        IsActive = true;
    }
}

回答2:

I have resolved this problem by overriding the SaveChanges method. See below for my solution.

Solution Explain

i) Override the SaveChanges method in the DbContext class.

public override int SaveChanges()
{
    return base.SaveChanges();
}

ii) Write logic to set default values

public override int SaveChanges()
{
    //set default value for your property
    foreach (var entry in ChangeTracker.Entries().Where(entry => entry.Entity.GetType().GetProperty("YOUR_PROPERTY") != null))
    {
        if (entry.State == EntityState.Added)
        {
            if (entry.Property("YOUR_PROPERTY").CurrentValue == null)
                entry.Property("YOUR_PROPERTY").CurrentValue = YOUR_DEFAULT_VALUE;
        }
    }

    return base.SaveChanges();
}

Example

i) Create Base Class

  public abstract class BaseModel
  {
       [Column(Order = 1)] 
       public long Id { get; set; }
       public long CreatedBy { get; set; }
       public DateTime CreatedDate { get; set; }
       public long ModifiedBy { get; set; }
       public DateTime ModifiedDate { get; set; }
       public bool IsActive { get; set; }
  }

ii) override SaveChanges

public override int SaveChanges()
{

    //set default value for IsActive property
    foreach (var entry in ChangeTracker.Entries().Where(entry => entry.Entity.GetType().GetProperty("IsActive") != null))
    {
        if (entry.State == EntityState.Added)
        {
            if(entry.Property("IsActive").CurrentValue == null)
                entry.Property("IsActive").CurrentValue = false;
        }
    }

    return base.SaveChanges();
}

来源：https://stackoverflow.com/questions/30945133/ef-6-codefirst-setting-default-value-for-a-property-defined-in-base-class-using

标签

entity-framework

entity-framework-6

ef-fluent-api