is there "elegant" way to give specific property a default value ?
Maybe by DataAnnotations, something like :
[DefaultValue("true")]
public bool Active { get; set; }
Thank you.
You can do it by manually edit code first migration:
public override void Up()
{
AddColumn("dbo.Events", "Active", c => c.Boolean(nullable: false, defaultValue: true));
}
It's been a while, but leaving a note for others.
I achieved what is needed with an attribute and I decorated my model class fields with that attribute as I want.
[SqlDefaultValue(DefaultValue = "getutcdate()")]
public DateTime CreatedDateUtc { get; set; }
Got the help of these 2 articles:
EF on CodePlex
Andy Mehalick blog
What I did:
Define Attribute
[AttributeUsage(AttributeTargets.Property, AllowMultiple = false)]
public class SqlDefaultValueAttribute : Attribute
{
public string DefaultValue { get; set; }
}
In the "OnModelCreating" of the context
modelBuilder.Conventions.Add( new AttributeToColumnAnnotationConvention<SqlDefaultValueAttribute, string>("SqlDefaultValue", (p, attributes) => attributes.Single().DefaultValue));
In the custom SqlGenerator
private void SetAnnotatedColumn(ColumnModel col)
{
AnnotationValues values;
if (col.Annotations.TryGetValue("SqlDefaultValue", out values))
{
col.DefaultValueSql = (string)values.NewValue;
}
}
Then in the Migration Configuration constructor, register the custom SQL generator.
SetSqlGenerator("System.Data.SqlClient", new CustomMigrationSqlGenerator());
The above answers really helped, but only delivered part of the solution.
The major issue is that as soon as you remove the Default value attribute, the constraint on the column in database won't be removed. So previous default value will still stay in the database.
Here is a full solution to the problem, including removal of SQL constraints on attribute removal.
I am also re-using .NET Framework's native DefaultValue attribute.
Usage
[DatabaseGenerated(DatabaseGeneratedOption.Computed)]
[DefaultValue("getutcdate()")]
public DateTime CreatedOn { get; set; }
For this to work you need to update IdentityModels.cs and Configuration.cs files
IdentityModels.cs file
Add/update this method in your ApplicationDbContext class
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
var convention = new AttributeToColumnAnnotationConvention<DefaultValueAttribute, string>("SqlDefaultValue", (p, attributes) => attributes.SingleOrDefault().Value.ToString());
modelBuilder.Conventions.Add(convention);
}
Configuration.cs file
Update your Configuration class constructor by registering custom Sql generator, like this:
internal sealed class Configuration : DbMigrationsConfiguration<ApplicationDbContext>
{
public Configuration()
{
// DefaultValue Sql Generator
SetSqlGenerator("System.Data.SqlClient", new DefaultValueSqlServerMigrationSqlGenerator());
}
}
Next, add custom Sql generator class (you can add it to the Configuration.cs file or a separate file)
internal class DefaultValueSqlServerMigrationSqlGenerator : SqlServerMigrationSqlGenerator
{
private int dropConstraintCount;
protected override void Generate(AddColumnOperation addColumnOperation)
{
SetAnnotatedColumn(addColumnOperation.Column, addColumnOperation.Table);
base.Generate(addColumnOperation);
}
protected override void Generate(AlterColumnOperation alterColumnOperation)
{
SetAnnotatedColumn(alterColumnOperation.Column, alterColumnOperation.Table);
base.Generate(alterColumnOperation);
}
protected override void Generate(CreateTableOperation createTableOperation)
{
SetAnnotatedColumns(createTableOperation.Columns, createTableOperation.Name);
base.Generate(createTableOperation);
}
protected override void Generate(AlterTableOperation alterTableOperation)
{
SetAnnotatedColumns(alterTableOperation.Columns, alterTableOperation.Name);
base.Generate(alterTableOperation);
}
private void SetAnnotatedColumn(ColumnModel column, string tableName)
{
if (column.Annotations.TryGetValue("SqlDefaultValue", out var values))
{
if (values.NewValue == null)
{
column.DefaultValueSql = null;
using var writer = Writer();
// Drop Constraint
writer.WriteLine(GetSqlDropConstraintQuery(tableName, column.Name));
Statement(writer);
}
else
{
column.DefaultValueSql = (string)values.NewValue;
}
}
}
private void SetAnnotatedColumns(IEnumerable<ColumnModel> columns, string tableName)
{
foreach (var column in columns)
{
SetAnnotatedColumn(column, tableName);
}
}
private string GetSqlDropConstraintQuery(string tableName, string columnName)
{
var tableNameSplitByDot = tableName.Split('.');
var tableSchema = tableNameSplitByDot[0];
var tablePureName = tableNameSplitByDot[1];
var str = $#"DECLARE #var{dropConstraintCount} nvarchar(128)
SELECT #var{dropConstraintCount} = name
FROM sys.default_constraints
WHERE parent_object_id = object_id(N'{tableSchema}.[{tablePureName}]')
AND col_name(parent_object_id, parent_column_id) = '{columnName}';
IF #var{dropConstraintCount} IS NOT NULL
EXECUTE('ALTER TABLE {tableSchema}.[{tablePureName}] DROP CONSTRAINT [' + #var{dropConstraintCount} + ']')";
dropConstraintCount++;
return str;
}
}
Your model properties don't have to be 'auto properties' Even though that is easier. And the DefaultValue attribute is really only informative metadata
The answer accepted here is one alternative to the constructor approach.
public class Track
{
private const int DEFAULT_LENGTH = 400;
private int _length = DEFAULT_LENGTH;
[DefaultValue(DEFAULT_LENGTH)]
public int LengthInMeters {
get { return _length; }
set { _length = value; }
}
}
vs.
public class Track
{
public Track()
{
LengthInMeters = 400;
}
public int LengthInMeters { get; set; }
}
This will only work for applications creating and consuming data using this specific class. Usually this isn't a problem if data access code is centralized. To update the value across all applications you need to configure the datasource to set a default value. Devi's answer shows how it can be done using migrations, sql, or whatever language your data source speaks.
What I did, I initialized values in the constructor of the entity
Note: DefaultValue attributes won't set the values of your properties automatically, you have to do it yourself
I admit that my approach escapes the whole "Code First" concept. But if you have the ability to just change the default value in the table itself... it's much simpler than the lengths that you have to go through above... I'm just too lazy to do all that work!
It almost seems as if the posters original idea would work:
[DefaultValue(true)]
public bool IsAdmin { get; set; }
I thought they just made the mistake of adding quotes... but alas no such intuitiveness. The other suggestions were just too much for me (granted I have the privileges needed to go into the table and make the changes... where not every developer will in every situation). In the end I just did it the old fashioned way. I set the default value in the SQL Server table... I mean really, enough already! NOTE: I further tested doing an add-migration and update-database and the changes stuck.
After #SedatKapanoglu comment, I am adding all my approach that works, because he was right, just using the fluent API does not work.
1- Create custom code generator and override Generate for a ColumnModel.
public class ExtendedMigrationCodeGenerator : CSharpMigrationCodeGenerator
{
protected override void Generate(ColumnModel column, IndentedTextWriter writer, bool emitName = false)
{
if (column.Annotations.Keys.Contains("Default"))
{
var value = Convert.ChangeType(column.Annotations["Default"].NewValue, column.ClrDefaultValue.GetType());
column.DefaultValue = value;
}
base.Generate(column, writer, emitName);
}
}
2- Assign the new code generator:
public sealed class Configuration : DbMigrationsConfiguration<Data.Context.EfSqlDbContext>
{
public Configuration()
{
CodeGenerator = new ExtendedMigrationCodeGenerator();
AutomaticMigrationsEnabled = false;
}
}
3- Use fluent api to created the Annotation:
public static void Configure(DbModelBuilder builder){
builder.Entity<Company>().Property(c => c.Status).HasColumnAnnotation("Default", 0);
}
It's simple! Just annotate with required.
[Required]
public bool MyField { get; set; }
the resultant migration will be:
migrationBuilder.AddColumn<bool>(
name: "MyField",
table: "MyTable",
nullable: false,
defaultValue: false);
If you want true, change the defaultValue to true in the migration before updating the database
In .NET Core 3.1 you can do the following in the model class:
public bool? Active { get; set; }
In the DbContext OnModelCreating you add the default value.
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Foundation>()
.Property(b => b.Active)
.HasDefaultValueSql("1");
base.OnModelCreating(modelBuilder);
}
Resulting in the following in the database
Note:
If you don't have nullable (bool?) for you property you will get the following warning
The 'bool' property 'Active' on entity type 'Foundation' is configured with a database-generated default. This default will always be used for inserts when the property has the value 'false', since this is the CLR default for the 'bool' type. Consider using the nullable 'bool?' type instead so that the default will only be used for inserts when the property value is 'null'.
I found that just using Auto-Property Initializer on entity property is enough to get the job done.
For example:
public class Thing {
public bool IsBigThing{ get; set; } = false;
}
using System.ComponentModel;
[DefaultValue(true)]
public bool Active { get; set; }
In EF core released 27th June 2016 you can use fluent API for setting default value. Go to ApplicationDbContext class, find/create the method name OnModelCreating and add the following fluent API.
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<YourTableName>()
.Property(b => b.Active)
.HasDefaultValue(true);
}
Just Overload the default constructor of Model class and pass any relevant parameter which you may or may not use. By this you can easily supply default values for attributes. Below is an example.
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace Aim.Data.Domain
{
[MetadataType(typeof(LoginModel))]
public partial class Login
{
public Login(bool status)
{
this.CreatedDate = DateTime.Now;
this.ModifiedDate = DateTime.Now;
this.Culture = "EN-US";
this.IsDefaultPassword = status;
this.IsActive = status;
this.LoginLogs = new HashSet<LoginLog>();
this.LoginLogHistories = new HashSet<LoginLogHistory>();
}
}
public class LoginModel
{
[Key]
[ScaffoldColumn(false)]
public int Id { get; set; }
[Required]
public string LoginCode { get; set; }
[Required]
public string Password { get; set; }
public string LastPassword { get; set; }
public int UserGroupId { get; set; }
public int FalseAttempt { get; set; }
public bool IsLocked { get; set; }
public int CreatedBy { get; set; }
public System.DateTime CreatedDate { get; set; }
public Nullable<int> ModifiedBy { get; set; }
public Nullable<System.DateTime> ModifiedDate { get; set; }
public string Culture { get; set; }
public virtual ICollection<LoginLog> LoginLogs { get; set; }
public virtual ICollection<LoginLogHistory> LoginLogHistories { get; set; }
}
}
Even from .NET Core 1.0, It is possible to set default values when you are using the code first approach. See the following code snippet.
using System.ComponentModel;
[DefaultValue(true)]
public bool Active { get; set; }
Read for more: Microsoft official docs
Lets consider you have a class name named Products and you have a IsActive field. just you need a create constructor :
Public class Products
{
public Products()
{
IsActive = true;
}
public string Field1 { get; set; }
public string Field2 { get; set; }
public bool IsActive { get; set; }
}
Then your IsActive default value is True!
Edite :
if you want to do this with SQL use this command :
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Blog>()
.Property(b => b.IsActive)
.HasDefaultValueSql("true");
}
The Entity Framework Core Fluent API HasDefaultValue method is used to specify the default value for a database column mapped to a property. The value must be a constant.
public class Contact
{
public int ContactId { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string Email { get; set; }
public bool IsActive { get; set; }
public DateTime DateCreated { get; set; }
}
public clas SampleContext : DbContext
{
public DbSet<Contact> Contacts { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Context>()
.Propery(p => p.IsActive)
.HasDefaultValue(true);
}
}
Or
like it!
You can also specify a SQL fragment that is used to calculate the default value:
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Blog>()
.Property(b => b.Created)
.HasDefaultValueSql("getdate()");
}
Hmm... I do DB first, and in that case, this is actually a lot easier. EF6 right? Just open your model, right click on the column you want to set a default for, choose properties, and you will see a "DefaultValue" field. Just fill that out and save. It will set up the code for you.
Your mileage may vary on code first though, I haven't worked with that.
The problem with a lot of other solutions, is that while they may work initially, as soon as you rebuild the model, it will throw out any custom code you inserted into the machine-generated file.
This method works by adding an extra property to the edmx file:
<EntityType Name="Thingy">
<Property Name="Iteration" Type="Int32" Nullable="false" **DefaultValue="1"** />
And by adding the necessary code to the constructor:
public Thingy()
{
this.Iteration = 1;
Set the default value for the column in table in MSSQL Server, and in class code add attribute, like this:
[DatabaseGenerated(DatabaseGeneratedOption.Computed)]
for the same property.
I've problem with seeding data to database. Eariler I tried way from this tut: Seed Data in EF 6 Code-First
and then the seed method is never called
DBSchool.cs
namespace SchoolTest.DAL
{
public class DBSchool : DbContext
{
public DBSchool() : base("DBSchool")
{
Database.SetInitializer(new Seeder());
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
}
public DbSet<Guest> Guests { get; set; }
}
}
Seeder.cs
public class Seeder : DropCreateDatabaseAlways<DBSchool>
{
protected override void Seed(DBSchool context)
{
IList<Guest> GuestList = new List<Guest>();
GuestList.Add(new Guest()
{
Name = "Dexter",
Surname = "Dexter",
Email = "test#test.com"
});
context.Guests.AddRange(GuestList);
context.SaveChanges();
base.Seed(context);
}
}
Guest.cs
public class Guest
{
public string Name { get; set; }
public string Surname { get; set; }
public string Email { get; set; }
[Key]
public int GuestId { get; set; }
}
App.config
<appSettings>
<add key="DatabaseInitializerForType SchoolTest.DAL.DBSchool, SchoolTest"
value="SchoolTest.Data.Seeder, SchoolTest" />
</appSettings>
Is there any way to call the Seed() method or just through the Configuration.cs?
Try changing your code like this.
public class DBSchool : DbContext
{
public DBSchool() : base("name=<database-name>")
{
Database.SetInitializer<DBSchool>(new Seeder());
}
// Rest of your implementation
}
Replace <database-name> with the name of your database.
If that didn't work, you can give a Generic Type Parameter to the context class and change your code as follows.
Seeder.cs -> public class Seeder<T> : DropCreateDatabaseAlways<DBSchool>
DBSchool.cs -> Database.SetInitializer<DBSchool>(new Seeder<DBSchool>());
Read more on that here.
If that didn't work either, you can use migrations and seed data using custom sql using Sql().
Using Entity Framework Core 2.0, I am trying to construct a query to include related data for a polymorphic child entity.
For example, given the following types:
public class ParentEntity
{
public int Id { get; set; }
public IList<ChildEntityBase> Children { get; set; }
}
public abstract class ChildEntityBase
{
public int Id { get; set; }
}
public class ChildEntityA : ChildEntityBase
{
}
public class ChildEntityB : ChildEntityBase
{
public IList<GrandchildEntity> Children { get; set; }
}
public class GrandchildEntity
{
public int Id { get; set; }
}
and the following configuration:
public DbSet<ParentEntity> ParentEntities { get; set; }
protected override void OnModelCreating(ModelBuilder builder)
{
builder.Entity<ParentEntity>().HasKey(p => p.Id);
builder.Entity<ParentEntity>().HasMany(p => p.Children).WithOne();
builder.Entity<ChildEntityBase>().HasKey(c => c.Id);
builder.Entity<ChildEntityBase>()
.HasDiscriminator<string>("ChildEntityType")
.HasValue<ChildEntityA>("a")
.HasValue<ChildEntityB>("b");
builder.Entity<ChildEntityA>()
.HasBaseType<ChildEntityBase>();
builder.Entity<ChildEntityB>()
.HasBaseType<ChildEntityBase>()
.HasMany(u => u.Children).WithOne();
builder.Entity<GrandchildEntity>()
.HasBaseType<ChildEntityBase>();
base.OnModelCreating(builder);
}
I am trying to write the following query:
var result = this.serviceDbContext.ParentEntities
.Include(p => p.Children)
.ThenInclude((ChildEntityB b) => b.Children);
Unfortunately, this is resulting in a syntax error.
However, I believe I am following the syntax as specified in https://github.com/aspnet/EntityFrameworkCore/commit/07afd7aa330da5b6d90d518da7375d8bbf676dfd
Can anyone suggest what I'm doing wrong?
Thanks
This functionality is not available in EFC 2.0.
It's been tracked as #3910 Query: Support Include/ThenInclude for navigation on derived type and according to the current EFC Roadmap, it's scheduled for EFC 2.1 release (Include for derived types item under
Features we have committed to complete).
I'm trying to setup a simple inheritance scenario with EF 4.3.1 using code first approch and fluent configuration.
I've created an abstract base type 'A' with a one-to-one navigation property and an inherited class 'AA' also with a one-to-one navigation property has following :
public abstract class A
{
public Guid ID { get; set; }
public B ChildB { get; set; }
}
public class AA : A
{
public C ChildC { get; set; }
}
public class B
{
public Guid ID { get; set; }
public A Parent { get; set; }
}
public class C
{
public Guid ID { get; set; }
public AA Parent { get; set; }
}
public class AConfiguration : EntityTypeConfiguration<A>
{
public AConfiguration()
{
this.HasRequired(o => o.ChildB)
.WithRequiredPrincipal(o => o.Parent);
this.Map(o =>
{
o.ToTable("A");
});
}
}
public class AAConfiguration : EntityTypeConfiguration<AA>
{
public AAConfiguration()
{
this.HasRequired(o => o.ChildC)
.WithRequiredPrincipal(o => o.Parent);
this.Map(o =>
{
o.ToTable("AA");
});
}
}
public class BConfiguration : EntityTypeConfiguration<B>
{
public BConfiguration()
{
this.HasRequired(o => o.Parent)
.WithRequiredDependent(o => o.ChildB);
this.Map(o =>
{
o.ToTable("B");
});
}
}
public class CConfiguration : EntityTypeConfiguration<C>
{
public CConfiguration()
{
this.HasRequired(o => o.Parent)
.WithRequiredDependent(o => o.ChildC);
this.Map(o =>
{
o.ToTable("C");
});
}
}
public class DataContext : DbContext
{
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Configurations.Add<A>(new AConfiguration());
modelBuilder.Configurations.Add<AA>(new AAConfiguration());
modelBuilder.Configurations.Add<B>(new BConfiguration());
modelBuilder.Configurations.Add<C>(new CConfiguration());
}
public DbSet<AA> AASet { get; set; }
public DbSet<B> BSet { get; set; }
public DbSet<C> CSet { get; set; }
}
When I try to get my data back with the first level of navigation property, it works as expected :
... dataContext.AASet.Include("ChildB") ...
But when I try to include the navigation property of the inherited type like following :
... dataContext.AASet.Include("ChildC") ...
I get an EntityCommandCompilationException at runtime with the following inner exception message :
The ResultType of the specified expression is not compatible with the
required type. The expression ResultType is
'Transient.reference[...A]' but the required type is
'Transient.reference[...AA]'. Parameter name: arguments[0]
Has anybody encountered a similar issue ?
I am probably missing something but I can't see what's wrong with this sample.
What can I do to get my model works as expected ?
No, you don't miss anything. Actually you ran into an old Entity Framework bug. Your second query can be written like this:
var result = dataContext.ASet.OfType<AA>().Include("ChildC").ToList();
(when you replace your DbSet AASet by ASet).
For this type of eager loading of one-to-one mapped children on inherited types this article applies: http://weblogs.asp.net/johnkatsiotis/archive/2010/04/28/huge-ef4-inheritance-bug.aspx
The bug has been reported long time ago here: https://connect.microsoft.com/VisualStudio/feedback/details/544639/ef4-inheritance-defined-using-queryview-doesnt-work-properly-with-association
The bug still exists in EF 4.3.1. But Microsoft has announced in this thread that the bug is fixed in .NET 4.5 ( = EF 5.0).
The code would work if the relationship is one-to-many instead of one-to-one. Lazy or explicit loading would work as well (also with one-to-one relationship), I believe:
var result = dataContext.ASet.OfType<AA>().ToList();
foreach (var item in result)
dataContext.Entry(item).Reference(a => a.ChildC).Load();
But this will generate multiple queries. If you don't have performance problems with multiple queries I would prefer the last workaround - until you can migrate to EF 5.0.