I have a table which links to another table in the ASP.NET membership schema.
Problem is, all the PKs for the ASP.NET tables are uniqueidentifier so mine has to be too. When I add a SqlDatasource and call its Insert() method, I get the following error:
Cannot insert the value NULL into column 'DiscountCode', table 'CreamDb.dbo.CustomInfo1'; column does not allow nulls. INSERT fails.
The statement has been terminated.
The uniqueidentifier is also treated as an object (its data type), but there is no Guid data type. I had this problem before, but the schema was much simpler so I could fix it.
How can I go about fixing this? If I get rid of the data type part in the markup (so just leave the field/parameter name but not the data type stuff), I get another error so that is not possible.
Thanks
What do you mean by "there is no Guid data type"? What's wrong with System.Guid? Can't you just use Guid.NewGuid(), set the field appropriately, and do the insert?
EDIT: Just to give a bit more meat: attach an event handler to the Inserting event, and populate the field then, via the DbCommand returned by SqlDataSourceCommandEventArgs.Command. Or change the SQL used by the INSERT command to ask the database to populate the GUID field for you.
A popullar approach when dealing with references to the ASP.NET Membership Provider's data is, instead of keeping a proper foreign key to the GUIDs, instead store something like the LoweredUserName in your table. Then, use the Membership Provider's API to interact with the object you need. In some cases, you need an ObjectDataSource abstraction layer to accomplish CRUD scenarios.
Set the default value of the column in SQL Sever to "newid()".
Asp.net won't send the value, and the field will get a new guid.
Related
I'm having a hard time debugging a particular problem and have a couple questions. First, here is what's going on:
I have a relatively simple table called Employees, which has a primary key / identity Id. There is also a Username column - which is a GUID foreign key to my aspnet_Users table used for membership. Finally, there is another foreign key Team_Id which points to another table, Teams.
All I'm really trying to do is give a selected employee's Id and pass it to a method in the DAL which then finds the employee with the following statement:
var employee = entities.Employees.Where(emp => emp.Id == employeeId);
Once the employee is retrieved, I want to use another value which is passed to the same method - the selected team's Id - to update the employee's Team_Id value (which team they are assigned to), using the following:
employee.First().Team_Id = teamId;
entities.SaveChanges();
I get the exception
Invalid column name: {Name}
which doesn't make sense to me, because Employee doesn't have a name column.
All of that said, my questions are:
Where could the mix up possibly be coming from? I've tried thinking up a way to step through the code, but it seems like the error is somewhere in the query itself so I'm not really sure how to trace the execution of the query itself.
Is it possible that it may have something to do with my generated Entities? I noticed that when I type employee.First(). Name comes up in Intellisense. I'm really confused by that, since as I've mentioned there is no Name column in the employees table.
Fixed the issue. I just removed the existing Entity Framework Model and re-added it.
As far as the query goes, you can always use SQL Profiler to watch what scripts are actually running. That's a good way to troubleshoot generated SQL anyway.
For your property, somehow that did make it to your class, so your data model thinks it's there, for whatever reason. I'd say just go to your data model (you don't mention if this this is EF or LINQ-to-SQL), and you'll see "Name" there. Just remove it, and it will remove it from the class, and from the data access stuff.
I am unable to understand the line in bold from this msdn page:-
http://msdn.microsoft.com/en-us/library/bb738618.aspx
SaveChanges can generate an UpdateException when an object added to the ObjectContext cannot be successfully created in the data source. This can happen if a row with the foreign key specified by the relationship already exists. When this occurs, you cannot use Refresh to update the added object in the object context. Instead, reload the object with a value of OverwriteChanges for MergeOption.
In a table, a foreign key column can have a single value multiple times. e.g. DepartmentID foreign key in Users Table: More than one User can have same DepartmentID foreign key.
So how can this cause an UpdateException ?
Easy. You have an entity in your context in the Added state with a PK value of something already in the DB. This is common when people try to use stub objects incorrectly. If you want more help than that, you need to isolate your problem and post your code.
i have two tables
asset employee
assetid-pk empid-pk
empid-fk
now, i have a form to populate the asset table but it cant because of the foreign key constraint..
what to do?
thx
Tk
Foreign keys are created for a good reason - to prevent orphan rows at a minimum. Create the corresponding parent and then use the appropriate value as the foreign key value on the child table.
You should think about this update as a series of SQL statements, not just one statement. You'll process the statements in order of dependency, see example.
Asset
PK AssetID
AssetName
FK EmployeeID
etc...
Employee
PK EmployeeID
EmployeeName
etc...
If you want to "add" a new asset, you'll first need to know which employee it will be assigned to. If it will be assigned to a new employee, you'll need to add them first.
Here is an example of adding a asset named 'BOOK' for a new employee named 'Zach'.
DECLARE #EmployeeFK AS INT;
INSERT (EmployeeName) VALUES ('Zach') INTO EMPLOYEE;
SELECT #EmployeeFK = ##IDENTITY;
INSERT (AssetName, EmployeeID) VALUES ('BOOK',#EmployeeFK) INTO ASSET;
The important thing to notice above, is that we grab the new identity (aka: EmployeeID) assigned to 'Zach', so we can use it when we add the new asset.
If I understand you correctly, are you trying to build the data graph locally before persisting to the data? That is, create the parent and child records within the application and persist it all at once?
There are a couple approaches to this. One approach people take is to use GUIDs as the unique identifiers for the data. That way you don't need to get the next ID from the database, you can just create the graph locally and persist the whole thing. There's been a debate on this approach between software and database for a long time, because while it makes a lot of sense in many ways (hit the database less often, maintain relationships before persisting, uniquely identify data across systems) it turns out to be a significant resource hit on the database.
Another approach is to use an ORM that will handle the persistence mapping for you. Something like NHibernate, for example. You would create your parent object and the child objects would just be properties on that. They wouldn't have any concept of foreign keys and IDs and such, they'd just be objects in code related by being set as properties on each other (such as a "blog post" object with a generic collection of "comment" objects, etc.). This graph would be handed off to the ORM which would use its knowledge of the mapping between the objects and the persistence to send it off to the database in the correct order, perhaps giving back the same object but with ID numbers populated.
Or is this not what you're asking? It's a little unclear, to be honest.
The short version:
I have a grid view bound to a data source which has a SelectCommand with a left join in it because the FK can be null. On Update I want to create a record in the FK table if the FK is null and then update the parent table with the new records ID. Is this possible to do with just SqlDataSources?
The detailed version:
I have two tables: Company and Address. The column Company.AddressId can be null. On my ascx page I am using a SqlDataSource to select a left join of company and address and a GridView to display the results. By having my UpdateCommand and DeleteCommand of the SqlDataSource execute two statements separated by a semi-colon I am able to use the GridView's Edit and Delete functionality to update both table simultaneously.
The problem I have is when the Company.AddressId is null. What I need to have happen is have the data source create a record in the Address table and then update the Company table with the new Address.ID then proceed with the update as usual. I would like to do this with just data sources if possible for consistency/simplicity sake. Is it possible to have my data source do this, or perhaps add a second data source to the page to handle some of this?
Once I have that working I can probably figure out how to make it work with the InsertCommand as well but if you are on a roll and have an answer for how to make that fly as well feel free to provide it.
Thanks.
execute two statements separated by a
semi-colon
I don't see any reason why it wouldn't be possible to do both an INSERT and UPDATE in two statements with SqlDataSource just like you are doing here.
However, just so you know, if you have a lot of traffic or users using the application at the same time, you can run into concurrently issues where one user does something that affects another user and unexpected results can cascade and mess up your data. In general, for things like what you are doing - INSERT and UPDATE involving primary or foreign keys, usually SQL TRANSACTIONs are used. But, you must execute them as SQL stored procedures (or functions), on your SQL database. You are still able to call them from your SqlDataSource however by simply telling it that you are calling a stored procedure.
I have web application where Iam using linq to business entites i have business data model.
the problem is :
I have table with one column that it dosen't allow null value, when I try to update this table the folloeing error arise:
error The property 'e.g Carrier' is part of the object's key information and cannot be modified
what I can do?
The easiest thing to do is add a second column to the table that has a unique key eg guid and create a read only property on the entity that corresponds to it.
Linq to business entites needs some kind of key to keep track of what to update in the database. Usually this is the primary key on the database table. If you dont have a primary key it cannot reliably update the database and will then send you an exception.
Also if there is no primary key explicitly set on the table linq to business entites will select one of the columns (think its the first column in the table but i could be wrong) to act as a primary key and will therefore not allow you to update it.