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 want to retrieve an object plus its filtered/ordered collection property using EF 5. However, my current code throws an exception:
The Include path expression must refer to a navigation property
defined on the type. Use dotted paths for reference navigation
properties and the Select operator for collection navigation
properties
Here is the class of the object I want to retrieve:
public class EntryCollection
{
[Key]
public int Id { get; set; }
public ICollection<Entry> Entries { get; set; }
...
}
And here is the definition of Entry:
public class Entry
{
[Key]
public int Id { get; set; }
public DateTime Added { get; set; }
...
}
I wanted to retrieve the EntryCollection which contains only the most recent entries, so here is the code I tried:
using (var db = new MyContext())
{
return db.EntryCollections
.Include(ec => ec.Entries.OrderByDescending(e => e.Added).Take(5))
.SingleOrDefault(ec => ec.Foo == "bar');
}
Any ideas?
You cant use OrderBy inside an include.
what about the following
using (var db = new MyContext())
{
return db.EntryCollections
.Where(ec => ec.Foo == "bar")
.Select(ec=> new Something{Entries = ec.Entries.OrderByDescending(e => e.Added).Take(5) }, /*some other properties*/)
.SingleOrDefault();
}
or do it in two seperate queries
I am in the process of creating a domain model and would like to have a "BaseEntity" class with an "Id" property (and some other audit tracking stuff). The Id property is the primary key and each Entity in my Domain Model will inherit from the BaseEntity class. Pretty straightforward stuff.....
public class BaseEntity
{
[Key]
public int Id { get; set; }
public DateTime LastUpdate { get; set; }
public string LastUpdateBy { get; set; }
}
public class Location : BaseEntity
{
[Required]
public string Name { get; set; }
public string Description { get; set; }
}
Using the example above, I would like to map the "Id" field to a "LocationId" column. I understand that I can use the modelBuilder to do this for each entity explicitly by doing something like this:
modelBuilder.Entity<Location>().Property(s => s.Id).HasColumnName("LocationId");
But I would like to do this for every Entity in my domain model and it would be ugly.
I tried the following bit of reflection but did not have any luck. For whatever reason, the compiler "cannot resolve symbol type":
foreach (var type in GetTypesInNamespace(Assembly.Load("Domain.Model"),"Domain.Model"))
{
modelBuilder.Entity<type>().Property(x=>x.Id).....
}
Is there a way to define a convention to override the default PrimaryKey convention to map my "Id" property to a "ClassNameId" property in the database? I am using Entity Framework 6.
You should take a look at Custom Code First Conventions. You need EF6 for it to work, but it looks like you're already using it.
Just to give you an overview, take a look at the following convention I've used to convert PascalCase names to underscore names. It includes a convention for id properties... It also includes an optional table name prefix.
public class UnderscoreNamingConvention : IConfigurationConvention<PropertyInfo, PrimitivePropertyConfiguration>,
IConfigurationConvention<Type, ModelConfiguration>
{
public UnderscoreNamingConvention()
{
IdFieldName = "Id";
}
public string TableNamePrefix { get; set; }
public string IdFieldName { get; set; }
public void Apply(PropertyInfo propertyInfo, Func<PrimitivePropertyConfiguration> configuration)
{
var columnName = propertyInfo.Name;
if (propertyInfo.Name == IdFieldName)
columnName = propertyInfo.ReflectedType.Name + IdFieldName;
configuration().ColumnName = ToUnderscore(columnName);
}
public void Apply(Type type, Func<ModelConfiguration> configuration)
{
var entityTypeConfiguration = configuration().Entity(type);
if (entityTypeConfiguration.IsTableNameConfigured) return;
var tableName = ToUnderscore(type.Name);
if (!string.IsNullOrEmpty(TableNamePrefix))
{
tableName = string.Format("{0}_{1}", TableNamePrefix, tableName);
}
entityTypeConfiguration.ToTable(tableName);
}
public static string ToUnderscore(string value)
{
return Regex.Replace(value, "(\\B[A-Z])", "_$1").ToLowerInvariant();
}
}
You use it like this
modelBuilder.Conventions.Add(new UnderscoreNamingConvention { TableNamePrefix = "app" });
EDIT: In your case, the Apply method should be something like this:
public void Apply(PropertyInfo propertyInfo, Func<PrimitivePropertyConfiguration> configuration)
{
if (propertyInfo.Name == "Id")
{
configuration().ColumnName = propertyInfo.ReflectedType.Name + "Id";
}
}
Try this out in your DbContext class;
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Properties<int>()
.Where(p => p.Name.Equals("Id"))
.Configure(c => c.HasColumnName(c.ClrPropertyInfo.ReflectedType.Name + "Id"));
}
int is the CLR Type of my Primary Key fields. I want to refer to all keys in code as Id but DBA's require keys to be Id with Table entity name prefix. Above gives me exactly what I want in my created database.
Entity Framework 6.x is required.
In Entity Framework 6 Code First:
modelBuilder.Entity<roles>().Property(b => b.id).HasColumnName("role_id");
and update-database...
Change in model
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public long id { get; set; }
to:
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public long role_id { get; set; }
Then remove this:
//modelBuilder.Entity<roles>().Property(b => b.id).HasColumnName("role_id");
A start to the Dynamic approach if NOT using custom conventions
modelBuilder.Entity<Location>().Property(s => s.Id).HasColumnName("LocationId");
You can do this using reflection on the context. Pseudo Code as explanation:
Reflect Context to get a list of POCO names
For each POCO in a dbcontext.
Map Property Id -> string PocoName+Id
Here are the extensions I use for this type of solution.
// DBSet Types is the Generic Types POCO name used for a DBSet
public static List<string> GetModelTypes(this DbContext context) {
var propList = context.GetType().GetProperties();
return GetDbSetTypes(propList);
}
// DBSet Types POCO types as IEnumerable List
public static IEnumerable<Type> GetDbSetPropertyList<T>() where T : DbContext {
return typeof (T).GetProperties().Where(p => p.PropertyType.GetTypeInfo()
.Name.StartsWith("DbSet"))
.Select(propertyInfo => propertyInfo.PropertyType.GetGenericArguments()[0]).ToList();
}
private static List<string> GetDbSetTypes(IEnumerable<PropertyInfo> propList) {
var modelTypeNames = propList.Where(p => p.PropertyType.GetTypeInfo().Name.StartsWith("DbSet"))
.Select(p => p.PropertyType.GenericTypeArguments[0].Name)
.ToList();
return modelTypeNames;
}
private static List<string> GetDbSetNames(IEnumerable<PropertyInfo> propList) {
var modelNames = propList.Where(p => p.PropertyType.GetTypeInfo().Name.StartsWith("DbSet"))
.Select(p => p.Name)
.ToList();
return modelNames;
}
However, you will still need to employee dynamic lambda to finish.
Continue that topic here: Dynamic lambda example with EF scenario
EDIT:
Add link to another question that address the common BAse Config class approach
Abstract domain model base class when using EntityTypeConfiguration<T>
Piggybacking on #Monty0018 's answer but this just need to be updated a little if, like me, you're using Entity Framework 7 and/or SQLite.
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
try
{
_builder = modelBuilder;
var typeName = typeof(T).Name;
_builder
.Entity(typeof(T))
.Property<int>("Id")
.ForSqliteHasColumnName(typeName + "Id");
}
catch (Exception e)
{
throw e;
}
}
I am currently using EF4.3 and Code First. Creation of my objects works (via my views - just using the auto-generated Create), but when I attempt to edit an object, it does not save any changes that, utlimately, tie back to my navigation properties. I have been reading on relationships, but I don't understand how to tell my context that the relationship has changed.
Here is some example code of my implementation.
#* Snippet from my view where I link into my ViewModel. *#
<div class="row">
<div class="editor-label">
#Html.LabelFor(model => model.ManagerID)
</div>
<div class="editor-field">
#Html.DropDownListFor(model => model.ManagerID, ViewBag.Manager as SelectList, String.Empty)
#Html.ValidationMessageFor(model => model.ManagerID)
</div>
</div>
Here is my Controller implementation (POST of my Edit):
[HttpPost]
public ActionResult Edit(ProjectViewModel projectViewModel)
{
if (ModelState.IsValid)
{
Project project = new Project();
project.ProjectID = projectViewModel.ProjectID;
project.Name = projectViewModel.Name;
project.ProjectManager = repository.GetUser(projectViewModel.ManagerID);
repository.InsertOrUpdateProject(project);
repository.Save();
return RedirectToAction("Index");
}
ViewBag.Manager = new SelectList(repository.GetUsers(), "UserID", "FullName", projectViewModel.ManagerID);
return View(projectViewModel);
}
Within my Project object:
public class Project
{
public int ProjectID { get; set; }
[Required]
public string Name { get; set; }
// Navigation Properties
public virtual User Manager { get; set; }
}
Here is the corresponding method from the repository (where my context resides):
public void InsertOrUpdateProject(Project project)
{
if (program.ProjectID == default(int))
{
context.Projects.Add(project);
}
else
{
context.Entry(project).State = EntityState.Modified;
}
}
Just to be clear, this does work to update my properties, but it does not update my navigation properties (in this case, Manager). Appreciate any help.
Setting the state to Modified only marks scalar properties as modified, not navigation properties. You have several options:
A hack (you won't like it)
//...
else
{
var manager = project.Manager;
project.Manager = null;
context.Entry(project).State = EntityState.Modified;
// the line before did attach the object to the context
// with project.Manager == null
project.Manager = manager;
// this "fakes" a change of the relationship, EF will detect this
// and update the relatonship
}
Reload the project from the database including (eager loading) the current manager. Then set the properties. Change tracking will detect a change of the manager again and write an UPDATE.
Expose a foreign key property for the Manager navigation property in your model:
public class Project
{
public int ProjectID { get; set; }
[Required]
public string Name { get; set; }
public int ManagerID { get; set; }
public virtual User Manager { get; set; }
}
Now ManagerID is a scalar property and setting the state to Modified will include this property. Moreover you don't need to load the Manager user from the database, you can just assign the ID you get from your view:
Project project = new Project();
project.ProjectID = projectViewModel.ProjectID;
project.Name = projectViewModel.Name;
project.ManagerID = projectViewModel.ManagerID;
repository.InsertOrUpdateProject(project);
repository.Save();
There are several options here, I will list 3 of them:
Option 1: Using GraphDiff
*This needs the Configuration.AutoDetectChangesEnabled of your context set to true.
Just install GraphDiff with NuGet
Install-Package RefactorThis.GraphDiff
Then
using (var context = new Context())
{
var customer = new Customer()
{
Id = 12503,
Name = "Jhon Doe",
City = new City() { Id = 8, Name = "abc" }
};
context.UpdateGraph(customer, map => map.AssociatedEntity(p => p.City));
context.Configuration.AutoDetectChangesEnabled = true;
context.SaveChanges();
}
For more details about GraphDiff look here.
Option 2: Find and Edit
Searching your entity with EF to track it to the context. Then edit the properties.
*This needs the Configuration.AutoDetectChangesEnabled of your context set to true.
var customer = new Customer()
{
Id = 12503,
Name = "Jhon Doe",
City = new City() { Id = 8, Name = "abc" }
};
using (var context = new Contexto())
{
var customerFromDatabase = context.Customers
.Include(x => x.City)
.FirstOrDefault(x => x.Id == customer.Id);
var cityFromDataBase = context.Cities.FirstOrDefault(x => x.Id == customer.City.Id);
customerFromDatabase.Name = customer.Name;
customerFromDatabase.City = cityFromDataBase;
context.Configuration.AutoDetectChangesEnabled = true;
context.SaveChanges();
}
Option 3: Using a scalar property
In a matter of performance this is the best way, but it mess your class with database concerns. Because you will need to create a scalar (primitive type) property to map the Id.
*In this way there is no need to set the Configuration.AutoDetectChangesEnabled to true. And also you won't need to do a query to the database to retrieve the entities (as the first two options would - yes GraphDiff does it behind the scenes!).
var customer = new Customer()
{
Id = 12503,
Name = "Jhon Doe",
City_Id = 8,
City = null
};
using (var contexto = new Contexto())
{
contexto.Entry(customer).State = EntityState.Modified;
contexto.SaveChanges();
}
I am not sure exactly what you mean by navigation properties? Do you mean like a foreign key relationship? If so then try the following data annotation:
public class Project
{
public int ProjectID { get; set; }
[Required]
public string Name { get; set; }
[ForeignKey("YourNavigationProperty")]
public virtual UserManager { get; set; }
}
Update your EF Context, and see what happens?
UPDATE
public class Project
{
public int ProjectID { get; set; }
[Required]
public string Name { get; set; }
[ForeignKey("ManagerId")]
public ManagerModel UserManager { get; set; }
}
public class ManagerModel
{
[Key]
public int ManagerId { get; set; }
public String ManagerName { get; set; }
}
See if that works?
This should be a simple one involving EF Code first but I can't wrap my head around the documentation and all the examples I am finding are from older versions. I am working with the latest (4.1).
Anyway I have some models like:
public class Foo
{
public int ID { get; set; }
public Bar Bar { get; set; }
}
public class Bar
{
public int ID { get; set; }
public string Value { get; set; }
}
I used some scaffolding with Asp.Net MVC to create my controllers/repositories and when I create a 'Foo' object, it also creates a 'Bar' object even though I set the 'Bar' property from something stored in the database.
public class FooViewModel
{
public int ID { get; set; }
public int BarID { get; set; }
}
public ActionResult Create(FooViewModel foo)
{
var entity = new Foo()
{
ID = foo.ID,
Bar = _barRepository.Find(foo.BarID)
};
_fooRepository.InsertOrUpdate(entity);
_fooRepository.Save();
// more stuff
}
How can I use fluent syntax for EF in order to stop it from creating a new 'Bar' row in the database?
Update
Here is the generated repository code:
public void InsertOrUpdate(Foo foo)
{
if (foo.ID == default(int)) {
// New entity
context.Foo.Add(foo);
} else {
// Existing entity
context.Foo(foo).State = EntityState.Modified;
}
}
public void Save()
{
context.SaveChanges();
}
your _fooRepository and _barRepository need to share same DB context instance. If the are using two instances the Bar will be in added state.
The problem must be somewhere in your repository layer - using the same model directly with EF 4.1 produces the expected result - a new row in the Foos table with a bar FK column pointing to the existing Bar.