Entity Framework - default values doesn't set in sql server table - c#

SQL server 2005 database table has a column 'createdon' for which default value set to getdate(). I am trying to add a record using entity framework. 'createdon' column is not getting updated.
Did I miss any property in Entity framework, please suggest.


This is one of the few issues that are problematic with Entity Framework. Say you have a class that looks like this:
public class MyEntity
{
// Id is a PK on the table with Auto-Increment
public int Id { get; set; }
// CreatedOn is a datetime, with a default value
public DateTime CreatedOn { get; set; }
}
Now, you want to insert a new element:
using(var context = new YourContext())
{
context.MyEntities.Add(new MyEntity())
}
Entity Framework knows how to handle an auto-increment primary key because of the definition in the EDMX. It will not try to insert a value for the Id property. However, as far as Entity Framework is concerned, CreatedOn has a value: the default DateTime. Because Entity Framework cannot say "well, it has a value but I should ignore it", it will actively insert the record with the CreatedOn property value, bypassing the default value on your column definition on your table.
There is no easy way to do this. You can either actively set the CreatedOn property to DateTime.Now when you insert that item. Or you can create an interface and an extension method pair:
public interface ICreatedOn
{
public DateTime CreatedOn { get; set; }
}
public partial class MyEntity : ICreatedOn
{
}
public static TEntity AsNew<TEntity>(this TEntity entity) where TEntity : ICreatedOn
{
if(entity != null)
entity.CreatedOn = DateTime.Now;
return entity;
}
using(var context = new YourContext())
{
context.MyEntities.Add(new MyEntity().AsNew())
}
Edit: To expand on this point, the reason why this is an unresolvable issue is because of the meaning behind an autoincrement field and a field with a default value constraint. An auto-increment field should, by definition, always be handle by the server, using a seed and all that jazz. You cannot specify a value for an auto-increment field on an insert unless you have used SET IDENTITY INSERT ON. A default value, however, is just a hint that say "if I don't specify any value, use this". Because value types in .NET cannot be null, there will always be a value and Entity Framework cannot infer that the default value for that field, at that time, means that you want it to be defaulted on the SQL server.


Next to using the designer and some more nifty stuff shown already, you can also mark the columns as being calculated by simply setting the DatabaseGenerated attribute on the field:
[DatabaseGenerated(DatabaseGeneratedOption.Computed)]
public DateTime CreatedOn { get; set; }


You can set StoreGeneratedPattern to Computed (as Malcolm suggested) in the GUI of the entity data model as well.
Open your .edmx file in Visual Studio
Open the properties of the field (click on the field -> hit
F4 or right click->properties)
Set StoreGeneratedPattern to Computed in the properties window
as shown below:


I've got around this issue by telling EF that the column is 'computed', and should therefore be left alone for inserts.
If you look in the configuration for the generated entity
namespace Data.Context
{
// Table
internal partial class MyTableConfiguration : EntityTypeConfiguration<MyTable>
{
public MyTableConfiguration(string schema = "dbo")
{
ToTable(schema + ".MyTable");
HasKey(x => x.Id);
Property(x => x.ColumnName).HasColumnName("ColumnName").IsOptional().HasDatabaseGeneratedOption(DatabaseGeneratedOption.Computed);
....

Related

SQLite seems to have a problem with [DatabaseGenerated(DatabaseGeneratedOption.Identity)]

I have a problem with the SQLite in-memory database. The normal database is working.
This is my model code
public class Log
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public Guid Id { get; set; }
public string Message { get; set; }
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public DateTime CreatedAt { get; set; }
}
The SQL statement to create the table
CREATE TABLE [dbo].[AuditLogs]
(
[Id] UNIQUEIDENTIFIER NOT NULL DEFAULT newid() PRIMARY KEY,
[Message] varchar(max) NOT NULL CONSTRAINT ensure_json CHECK (ISJSON([Message])> 0),
[CreatedAt] datetime NOT NULL default GetDate()
)
The error
Microsoft.Data.Sqlite.SqliteException (0x80004005): SQLite Error 19: 'NOT NULL constraint failed: AuditLogs.CreatedAt'.
Do you have any solution?

You could just use this:
public Guid Id { get; set; } = Guid.NewGuid();
The problem with the Entity Framework is that it won't generate keys for you. If it is database-generated then some trigger in the database would still need to create this ID. This is generally done when the ID is of type int, but not Guid. Then again, SQLite is a weird database provider to begin with as it doesn't really has datatypes. Data type definitions are more suggestions and not enforced by the engine. (But EF will enforce it.)
Anyways, since you use Guids there's nothing wrong with assigning new values to the property, as they will be overwritten by the value in the database on retrieval. But SQLite isn't really generating values for you.
Also, I would use public DateTime CreatedAt { get; set; } = DateTime.Now(); for the same reason. I myself actually had similar problems but I use the Fluid API instead and use this:
var hostBuilder = modelBuilder.Entity<Host>();
hostBuilder
.Property(r => r.Id)
.HasColumnOrder(0)
.IsRequired()
.HasColumnName("Key")
.HasColumnType("varchar(36)")
.HasComment($"Primary key");
hostBuilder
.Property<DateTime>("Created")
.HasColumnOrder(1)
.HasDefaultValueSql("CURRENT_TIMESTAMP")
.ValueGeneratedOnAdd()
.HasComment($"When was it created?");
hostBuilder
.HasKey(r => r.Id)
.HasName($"PK_Visitor_Host_Key");
And my class only has the Id property defined, as I don't need the Created field in my project. It still gets added, though! The HasDefaultValueSql() call will tell that the field is database-generated, including how it's generated. You might want to look into this Fluid API for your project. I prefer it over those attributes as it provides more options and better control, plus I can add fields to tables that are not important for my code, yet still required for other purposes...
(Btw. You don't want timestamps to be unique as two records could be created at exactly the same timestamp on fast systems.)

Dapper ignore property runtime

Is there a way to ignore property from being mapped in runtime. Because I don't know if database has specific column and I have to check it before doing insert. If database doesn't have column then I want to ignore this one specific property.
UPDATE:
Here's my insert code
public static void Insert(string connectionString, T entity)
{
using (var connection = new SqlConnection(connectionString))
{
connection.Open();
connection.Insert(entity);
}
}

That Insert method is part of Dapper.Contrib, not Dapper itself. As the Readme for that library explains, you can use the [Write(false)] attribute to specify that a property isn't writeable, eg :
public class MyClass
{
public int ID {get;set;}
public DateTime Created{get;set;}
[Write(false)]
public DateTime CreatedDate =>Created.Date;
}
The source code shows that Dapper.Contrib simply ignores properties that aren't writable :
var properties = type.GetProperties().Where(IsWriteable).ToArray();
Dapper is a microORM, it doesn't offer the mapping features found in full ORMs like EF or NHibernate. Dapper.Contrib adds some helper methods and very basic mapping through 5 atrributes:
[Table("Tablename")] to specify the table name
[Key] to mark an auto-generated key field
[ExplicitKey] to mark a field that isn't generated automatically
[Write(true/false)] to mark (non)writable properties
[Computed] to mark calculated properties.
There's no way to specify a column name for example

Unable to insert an explicit value in the EF Core identity column [duplicate]

I'm getting this error on EF.
Cannot insert explicit value for identity column in table
'GroupMembers_New' when IDENTITY_INSERT is set to OFF.
The column on the Db is identity increment and on the EF design file, StoreGeneratedPattern is identity as well. Seems like EF is trying to insert 0 every time I try to save.
Some suggestions says ID is reserved on tables or drop the table and rerun the scripts.
Any ideas?
Here's some code:
GroupMember groupMember = new GroupMember();
groupMember.GroupId = group.Id;
groupMember.UserId = (new UserId(group.Owner));
//groupMember.Id = _groupContext.GroupMembers.Count();
group.GroupMembers.Add(groupMember);
_groupContext.SaveChanges();

I have run into this before. This error means you are trying to assign a value explicitly to a column where the database automatically assigns it.
Suggestion:
Update your edmx file to reflect any changes you may have made in the database.
If the database automatically assigns the value, you should see the "IsDbGenerated=true" attribute in your designer file under that property. If it's not there, you can add it manually.

Try this:
using System.ComponentModel.DataAnnotations.Schema;
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
public decimal Identity_Col { get; set; }
The Entity Framework class file adds these lines of code to the Identity column.

Put these attribs on top of the property which is identity:
[Key]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
public int ID { get; set; }

I encountered the same problem and error message in my AspNetCore 2.x application.
The only way I could solve it was by removing this line in the ModelBuilder.Entity method of the DbContext class:
// remove: entity.Property(e => e.Id).ValueGeneratedNever();

EF Code first: Because of an auto-increment PK 'id' field AND a guid column, design like this:
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public Guid FileToken { get; set; }
there was a duplicate identity. I changed it to:
[DatabaseGenerated(DatabaseGeneratedOption.Computed)]
[DefaultValue("newid()")]
public Guid FileToken { get; set; }
and the problem went away.

In EF 6, there is a property of the field/column in your model for doing this:
StoreGeneratedPattern.
Set this to "Identity" in the property dropdown list.
(I don't know about EF 4. The above answer, using IsDbGenerated, seems to be for EF 4.)
And this corresponds in the underlying XML to an attribute to the element:
<Property Name="MyTableId" Type="int" Nullable="false" StoreGeneratedPattern="Identity" />
--but you don't need to deal with the XML manually, since you can use the designer.
How this gets messed up isn't clear. I had the problem even after refreshing my model from the database. Perhaps it gets confused if you set the PK on the table, or change its name, after you have already generated the model. (I am using the table/database-first approach, not code first.)
You can't use the above approach of putting the C# attribute on the entity code, because in this situation the entity code is generated by EF. EF is supposed to understand ("by itself") that the field is an identity.

I had this issue in my app; and got fixed it changing the property "StoredGeneratedPattern" of the id field to Identity.
So, Go to the model; look up for the table; click on propierties of the primary key fiel; and change the property.

See intercepting Entity Insert for generated always columns like StartTime and EndTime columns on history tables, rowversion columns as well.

I solved this by removing primary key in model from inserting data. because primary key auto increment.
var book = new Book
{
// Id = 1, //Don't need to write this
Genre = "Technology",
Author = "Charles Petzold",
Title = "Programming Windows 5th Edition",
Price = 30,
Publisher = "Microsoft Press"
};
_unitOfWork.Books.Add(book);

Well, You need give a value to ID, for example for the object Auto, just you should VarAuto.Id = 0;
After that you could do it something like this =>
using( MyContext db = new MyContext()){
db.Autos.Add(VarAuto);
db.SaveChanges();
}
That is the solution just give value to id, EF could be recognize the identity value in the table.
Just Try.

I'm using DB first and the table has identity column. I didn't use the db-scaffolding to generate this, I copied it from another entity and by mistake I took this property with.
So
Try to check the DBContext Class. I got this error, and the issue was with this property ".ValueGeneratedNever()"
I have just removed it and it works fine,
modelBuilder.Entity<TableName>(entity =>
{
entity.Property(e => e.Id)
//.ValueGeneratedNever()
.HasColumnName("ID");
});

Note: a moderator deleted this answer as a duplicate and left my other answer up, on a question with only the sql-server tag (which was the first question I arrived at from google). Since this question has the entity framework tag, posting the answer again here.
This is for EntityFramework Core 3.1.22. Using the wrong property to specify a foreign key causes Entity Framework to demote the primary key to ... something else. Entity Framework will then always attempt to insert an explicit value, which throws a database exception because it can't insert the value it's been told is a primary key and shouldn't be inserted.
Microsoft.EntityFrameworkCore.DbUpdateException: 'An error occurred while updating the entries. See the inner exception for details.'
Inner Exception:
SqlException: Cannot insert explicit value for identity column in table 'FOO' when IDENTITY_INSERT is set to OFF.
Code example. We have a 1-to-1 class mapping:
public class Foo /* child */
{
public int FooPrimaryKey { get; set; }
public int BarPrimaryKey { get; set; }
public virtual Bar PropertyBar {get; set; }
}
public class Bar
{
public int BarPrimaryKey { get; set; }
public virtual Foo PropertyFoo {get; set; }
}
modelBuilder.Entity<Foo>(entity =>
{
entity.HasKey(e => e.FooPrimaryKey);
entity.ToTable("FOO", "dbo");
entity.HasOne(d => d.PropertyBar)
.WithOne(x => x.PropertyFoo)
// wrong, this throws the above exception
.HasForeignKey<Bar>(x => x.BarPrimaryKey);
});
The foreign key should instead be (same key, different type):
.HasForeignKey<Foo>(x => x.BarPrimaryKey);

If you don't want to use EF core's auto-generating primary key values feature, you can turn it off. You can add your data to the primary key
It should resolve the error - Set Identity Insert off
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public int StudentId { get; set; }
Setting Database Generation option to None helped me.
You can find more about it here- https://learn.microsoft.com/en-us/ef/core/modeling/generated-properties?tabs=data-annotations

Add this line in order to allow the Id column to receive 1,2,3 and 4 values instead of being auto-numbered.
Sql("SET IDENTITY_INSERT MembershipTypes ON")

Database default value is not inserted while create record by entity framework

I have a LoginRecord table in sqlserver 2008 with the following column structure-
LoginId - int, identity
UserId - int
LoginDateTime- Allow nulls false,default value getdate()
I am inserting new record by entity framework 6 as below-
db.LoginRecords.Add(new LoginRecord() { UserId = UserId });
db.SaveChanges();
But in LoginDateTime table, null value is being inserted. It supposed to be current datetime.
I am using database first approach.
How can overcome this issue?

Combined my two comments into an answer.
Try setting the "StoredGeneratedPattern" attribute of your datetime in the EDMX file to Computed. From the following thread: http://www.stackoverflow.com/a/4688135/2488939
To do this, go to the edmx file designer by clicking on your edmx file. Then locate your table and the property. Right-click the column in the table that you want to change and click on properties. The property window should then come up and you will see as one of the properties "StoredGeneratedPattern". Change that to computed.

In addition to changing the EDMX file as suggested by Vishwaram Maharaj, you should make the definition of the table match between EF and the DB. The table description of "LoginDateTime- Allow nulls false" is itself false. The field clearly allows NULLs if NULLs are being inserted. Alter the column to not allow NULL if it truly shouldn't have NULL values in it:
ALTER TABLE LoginRecords ALTER COLUMN LoginDateTime DATETIME NOT NULL;

Setting default values in Entity Framework 5 and 6 by changing T4 Template File
Made below changes in .tt(template file)
Example:
red means remove and green means add
This will add constructor in all entity classes with OnCreated method.
Like below
public partial class Category
{
public Category()
{
this.Products = new HashSet<Product>();
OnCreated();
}
partial void OnCreated();
public int Id { get; set; }
public string Name { get; set; }
public virtual ICollection<Product> Products { get; set; }
}
Then create class file using same namespace that of Entities.
public partial class Category
{
partial void OnCreated()
{
Name = "abc"
}
}
Refer this
https://www.youtube.com/watch?v=i8J2ipImMuU
Helpfull

Entity Framework 6 Code First default datetime value on insert

When I'm saving changes to the database, I'm running into the following exception:
Cannot insert the value NULL into column 'Registered', table
'EIT.Enterprise.KMS.dbo.LicenseEntry'; column does not allow nulls.
INSERT fails. The statement has been terminated.
The related code first model property looks like this:
[DatabaseGenerated(DatabaseGeneratedOption.Identity), DataMember]
public DateTime Registered { get; private set; }
... and here's why I'm confused: As far as I know, by providing the annotation [DatabaseGenerated(DatabaseGeneratedOption.Identity) I'm ordering Entity Framework to auto-generate the field (in this case: Only once at creation time.)
So I'm expecting to have a non-nullable (required) field, without the possibility to alter the field manually where EF is taking care of.
What am I doing wrong?
Notes:
I don't want to use Fluent-API, as I want to use POCOs.
The property defaultValueSql is also not an option, because I need to rely database independed for this project (e.g. for GETDATE()).
I'm using Entity Framework 6 alpha 3, Code First.

Try this:
[DatabaseGenerated(DatabaseGeneratedOption.Identity), DataMember]
public DateTime? Registered { get; private set; }
The question mark makes the property nullable

There is no default DateTime. Only a min value.
You could potentially just set the datetime on that entity before calling dbContext.SaveChanges.
See this for a solution.

This technique behaves like a readonly field that is persisted to the database. Once the value is set it cannot (easily) be changed by using code. (Of course, you change the setter to public or internal if needed.)
When you create a new instance of a class that uses this code Registered will not initially be set. The first time the value of Registered is requested it will see that it has not been assigned one and then default to DateTime.Now. You can change this to DateTime.UTCNow if needed.
When fetching one or more entities from the database, Entity Framework will set the value of Registered, including private setters like this.
private DateTime? registered;
[Required]
public DateTime Registered
{
get
{
if (registered == null)
{
registered = DateTime.Now;
}
return registered.Value;
}
private set { registered = value; }
}

What I did was I set value as optional and nullable. I used Data Annotation, but its also possible to use IsOptional in Fluent Api:
[DatabaseGenerated(DatabaseGeneratedOption.Computed)]
public DateTime? UpdatedAt { get; set; }
Then I created another Sql migration, to alter value to default:
public partial class AlterTableUpdatedAtDefault : DbMigration
{
public override void Up()
{
Sql(#"ALTER TABLE dbo.[Table]
ADD CONSTRAINT DF_Table_UpdatedAt
DEFAULT getdate() FOR UpdatedAt");
}
public override void Down()
{
Sql(#"ALTER TABLE dbo.[Table]
drop CONSTRAINT DF_Table_UpdatedAt");
}
}

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