My MS SQL 2014 database table has a computed property column which uses a database function. Using SQL Server Management Studio, a query against the table lists the computed property values as expected.
The Codefluent model created via the import wizard shows the Entity with the computed column as a property. The underlying .cpf file defines the property with "d3p1:compute=" and the list of parameters that are used by the database function.
When an entity or the collection of entities is loaded, the properties which are used in the computed property have values, yet the computed property has a value of nothing/null.
How do I get Codefluent to read the computed value from the database table and have the value included in the entity's properties?
This is a bit tricky. First of all, you should declare the property like any other property. Then you must instruct the SQL producer to declare a formula on that column. You can do that with a custom 'compute' attribute in the SQL producer namespace. You can set it with the Visual Studio modeler like this:
In this example I've created an int property that is just another column value multiplied by 2.
Optionally, you can declare the property to be 'read on save' because most of the time, you want to read the computed value after a save, not only on load operations:
Once this is all done, this sample console app should display 30:
class Program
{
static void Main(string[] args)
{
var c = new Customer();
c.Name = "killroy";
c.Age = 15;
c.Save();
Console.WriteLine(c.Age2); // will display 30
}
}
If Simon Mouriers solution solves your problem than that is probably the best approach. However, there are 2 other options
RAW View Method
After you create a Codefluent Entities View click on the Edit Where button and it will allow you to create a RAW View
You can than specify the advanced property "UsedForMethods".
WARNING: Related entities will use the table instead of the view. This is by design and there is an article somewhere on the knowledge center on how to get around it. http://www.softfluent.com/product/codefluent-entities/knowledge-center/
Rename SQL Tables and Create a SQL View with the Same Name as the Original Table - This method is a hack, Softfluent discourages this approach, I love it because I know exactly what is happening under the scenes. I have used it with success in a scenario in which I needed soft deletes. I have automated the process with 2 stored procedures that handle the renaming. Using this approach requires running one of the stored procedures to undo the name changing prior to building the model. The other stored procedure handles the renaming after building the model. I'll post the stored procedures and how I use them within a couple of days.
Related
I have a legacy database with a particular table -- I will call it ItemTable -- that can have billions of rows of data. To overcome database restrictions, we have decided to split the table into "silos" whenever the number of rows reaches 100,000,000. So, ItemTable will exist, then a procedure will run in the middle of the night to check the number of rows. If numberOfRows is > 100,000,000 then silo1_ItemTable will be created. Any Items added to the database from now on will be added to silo1_ItemTable (until it grows to big, then silo2_ItemTable will exist...)
ItemTable and silo1_ItemTable can be mapped to the same Item entity because the table structures are identical, but I am not sure how to set this mapping up at runtime, or how to specify the table name for my queries. All inserts should be added to the latest siloX_ItemTable, and all Reads should be from a specified siloX_ItemTable.
I have a separate siloTracker table that will give me the table name to insert/read the data from, but I am not sure how I can use this with entity framework...
Thoughts?
You could try to use the Entity Inheritance to get this. So you have a base class which has all the fields mapped to ItemTable and then you have descendant classes that inherit from ItemTable entity and is mapped to the silo tables in the db. Every time you create a new silo you create a new entity mapped to that silo table.
[Table("ItemTable")]
public class Item
{
//All the fields in the table goes here
}
[Table("silo1_ItemTable")]
public class Silo1Item : Item
{
}
[Table("silo2_ItemTable")]
public class Silo2Item : Item
{
}
You can find more information on this here
Other option is to create a view that creates a union of all those table and map your entity to that view.
As mentioned in my comment, to solve this problem I am using the SQLQuery method that is exposed by DBSet. Since all my item tables have the exact same schema, I can use the SQLQuery to define my own query and I can pass in the name of the table to the query. Tested on my system and it is working well.
See this link for an explanation of running raw queries with entity framework:
EF raw query documentation
If anyone has a better way to solve my question, please leave a comment.
[UPDATE]
I agree that stored procedures are also a great option, but for some reason my management is very resistant to make any changes to our database. It is easier for me (and our customers) to put the sql in code and acknowledge the fact that there is raw sql. At least I can hide it from the other layers rather easily.
[/UPDATE]
Possible solution for this problem may be using context initialization with DbCompiledModel param:
var builder = new DbModelBuilder(DbModelBuilderVersion.V6_0);
builder.Configurations.Add(new EntityTypeConfiguration<EntityName>());
builder.Entity<EntityName>().ToTable("TableNameDefinedInRuntime");
var dynamicContext = new MyDbContext(builder.Build(context.Database.Connection).Compile());
For some reason in EF6 it fails on second table request, but mapping inside context looks correct on the moment of execution.
I have an one entity in my edmx model having an one property that can contains huge XML data.
Basically I want to load this entity without this property (column) /* huge data loading */ . And load this column only when it is strictly needed.
I have tried to create an inherited entity containing this property and remove this property from base entity (original entity). I have done mapping.
At this time I have problem, that during compilation a I get error, that base entity is not capable to insert and update itself, because property is not nullable
I am looking for best approach (solution) how this situation should be solved.
I am attaching the cut-out from my emdx designer (containing my current and desired situation)
UPDATE:
I will try to write a procedure that I have tried:
I mapped functions to my custom functions. For entity TRP_TechReport_T without the XML column (property). Then I just mapped for entity TRP_TechReport_T functions to my custom function (containing XML column).
Then I set Mapping condition on the entity TRP_TechReport_T: When TRP_XML = Empty.String
TechReport_T mappings:
TechReport_T functions:
TechReportFull_T mappings:
TechReportFull_T functions:
At this moment I get error:
Error 2 Error 3032: Problem in mapping fragments starting at line 3754:Condition member 'TRP_TechReport_T.TRP_XML' with a condition other than 'IsNull=False' is mapped. Either remove the condition on TRP_TechReport_T.TRP_XML or remove it from the mapping.
The column is not nullable in the database and mustn't be.
I can hard-set XML property to nullable, but in the case of the model updating from the database information will be lost.
At the moment it's the only thing I could think of.
I am using EF 4.1, code first and want a property on a customer entity built up of a constant string value and the customerId zero padded to act as a customer reference.
I might be being a bit daft but am struggling to work out how I can achieve this without
A) having to savechanges twice, once to get the Id then set my reference and save again
B) having a partial Customer class that simply provides a getter returning constant + CustomerId.Tostring("000000")
Is this "doable" with code first?
If you can change the database I would make a computed column for this. Thus, you leave it to the database to generate a reference value and it will also be available to other consumers of the database (if any).
Your Customer class will have a property like CustomerReference (string) that maps to the computed column and that is configured to have DatabaseGeneratedOption.Computed which will cause EF to read the value after inserting an object.
Using Entity Framework CodeFirst, how do I create a created datetime column that gets populated with the current timestamp everytime a record is inserted for that table, and a modified datetime column that has a timestamp generated evertime a row is updated? Rails does this by default and I was hoping the EF generated database would have this as well, but it doesn't. Is this something that can be done with data annotations? If so, how?
Thanks!
It is not supported in EF. EF will not create these columns for you automatically. You must do it yourselves by either:
Have Created and Modified properties in every entity where you want to maintain these values. You must also manually maintain these columns in your application (common approach is overriding SaveChanges and set values accordingly).
If you don't need these values mapped (you never expect to use them in your application and you are happy with the logic in the database) you can create custom database initializer which would execute your custom SQL to alter tables and add those columns, default constraints for Created columns and update triggers for Modified columns.
We've started using Entity Framework 4 for data access and have come across an issue or perhaps lack of understanding.
Our current system is heavily reliant on Stored Procedures, these procedure contain some necessary business logic so we need to continue to use these when doing Select/Insert/Update/Delete.
The issue we are having is the following:
We've mapped a table to an entity, let's say for example this is a User entity and has the following properties - UserId, FirstName, LastName
Now in our sproc to insert a user we accept FirstName, LastName, CreatedById as parameters.
As our User Entity has no CreatedById we get an error indicating that no property of our Entity can be mapped to the "CreatedById" parameter.
Now one thing we've tried is to manually add a CreatedById scalar property to our Entity, but this results in the issue that there is no Field in our User table in the data source that maps to CreatedById. In general the additional property that we'd like to pass in is not something that is stored.
Now there is potential solution to this in that we can just map the procedures to Function Imports and not bother with using the .AddObject, .DeleteObject, .SaveChanges way of manipulating our objects but that doesn't feel like the way to go about it.
that's a good question. There are few options i can tell u.
instead of mapping the entity to the table, map it a view and have the view return CreatedById and then your problem would be solved.
Second option is to create overloaded stored procedure that takes only FirstName, LastName and calls the actual stored procedure with a default value for CreatedById. You can create overloads at the database layer or create it in the model in the ssdl layer which supports inline stored procedure.
exec myproc #firstName,#LastName,null