Updating A Foreign Key To Null Value Using Nhibernate?
Jan 31, 2011
I have two table BuildGroup and table DocumentTemplate. DocumentTemplate table has BuildGroupId as foreign key which is nullable. In a certain senario I update BuildGroupId in DocumentTemplate table.
[Code].....
In another senario I need to set BuildGroupId in DocumentTemplate table again to dbnull.value. I tried with different cases as in else block. It giving the error : Cannot implicitly convert type 'System.DBNull' to 'int'. How can I update a foreign key value with NULL?
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Oct 2, 2010
I have 2 table Table A, Table B.
Table A - Parent Table
ID - Uniqueidentifier not null(PK)
Table B -Child Table
ID - uniqueidentifier null(FK, TableA)
I have a stored procedure to insert data into Table B, but when I tried to insert a null value into column ID of table B, this error came up:
The INSERT statement conflicted with the FOREIGN KEY constraint "FK_tableB_tableA". The conflict occurred in database "database name", table "table A", column 'ID'.
The statement has been terminated.
The insert statement in asp.net is like so:
sqlcommand.parameter.add(New Sqlparameter("ID", Nothing))
I am guessing adding nothing to the null value column is the problem, but i don't know how to fix it... The INSERT statement conflicted with the FOREIGN KEY constraint "FK_tableB_tableA". The conflict occurred in database "database name", table "table A", column 'ID'.
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Nov 6, 2010
i am using the following in a stored procedure.
[code]....
[Code]....Handling NULL...Field not updating when NULL?
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Sep 24, 2010
here's the situation:
You're using NHibernate with Fluent NHibernate for mappings.
You have an application in production with a database with live data You're adding a new feature in development and it requires a new database column.
The new column cannot be blank. For example, I recently had to a DateCreated column to a table and the app now uses that date. As the only time the data will be missing is now, it seems unnecessary to add code to check for errors.
In my application I have an updater which can execute a SchemaUpdate to add the new database column - however, the application will starting crashing as it is expecting a value in the new column.
I need to get some sensible default data into that column. In this case I manually ran an Update to set the date to the current date (good enough for the situation). In this particular case I believe that you cannot set the column default to getdate() using fluent mappings.
Keep a schema version number in a config file In the updater that runs SchemaUpdate start adding upgrade methods for each version. These methods would run updates to add default data (or other required actions).
After the schema update has been run, call all methods required for a version greater than the current version (i.e. those that haven't previously been run). So if the app is now version 4 and version 2 is installed, methods 3 and 4 would be run.
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Mar 8, 2011
I have the following models & mappings (code snippets further below).
One Competition has to have multiple CompetitionAnswers associated with it (multiple choice) from the outset.
At present, using the Fluent NHibernate mappings shown below, when I create a brand new Competition object, populate the properties, then create 3 brand new CompetitionAnswer objects and add them to the CompetitionAnswers property (property on Competition), I would expect to call Save on the session which would INSERT the 1 Competition row and 3 CompetitionAnswer rows to the DB.
However, as soon as I try to call Save on the session, it complains that CompetitionId is null and it can't insert a null into the CompetitionAnswers table for that field - which is right, it shouldn't, however, I assumed that the NHibernate would first create the Competition, then use the newly generated IDENTITY value (CompetitionId) in the CompetitionAnswers table?
[code]....
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Nov 17, 2010
I would like to know if the forieng key should be nullable or not. We shuld struggle for not making it nullable as much as possible or it doenst matter.
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Apr 8, 2010
I'm trying to insert a new EF object containing a reference to a related table via foreign key, and cannot get the reference stored in the new object. I have two tables in a SQL Server 2008 Database:
Component Templates
PartGroups
with a Foreign Key linking them thus: ComponentTemplates:ID [0..1<->*] PartGroups:ComponentTemplateID
I have imported these tables into a .NET web application project .edmx file (using a new ADO.NET Entity Data Model), and then created a Data Service which I then reference in a Silverlight 3.0 project. The objects are available as expected in the data context called by my Silverlight app and load correctly. Now, when I try to save a reference of ComponentTemplate into a newly created PartGroup, the PartGroup object is created in the database, but the value of ComponentTemplateID in the newly created table record is NULL.
[Code]....
(Note that _ctCtrl.ComponentTemplate is a confirmed non-NULL object reference to the parent object on which PartGroup is a child)
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Jan 12, 2011
This must be a common problem but I haven't been able to find an answer.I have dropdownlist that maps from a SQL foreign key, which can be NULL. Currently, I've added a "Please select..." to the top of my dropdown list and assigned it a value of 0.I know how to map from the drop down list to SQL using a CASE statement in my UpdateCommand.But how to I map from the SELECT statement to my dropdownlist? If this foreign key contains null I get "Item not in Dropdown list". I'd like to show "Please Select..." as the dropdownlist item if the SQL item contains NULL. I saw something online that says to use the value '''' for 'Please select...', but I don't think it's right, plus it doesn't work.Do I have to do something in my SELECT statement or do I have to do something on DDL.Databind?
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May 7, 2015
This is my UserRoleList.aspx.cs Code where i am passing the session variable to the page Default.aspx.cs..
And the error is: Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints. I have gone through many pages , and tried by making the AllowDbNull property making True and then different things.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
[code]...
This is the code of the second page Default.aspx.cs where i have to user the session varaible to pass in the SQL fucntion named GetDataByUserId as shown below:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
[Code] ....
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Apr 22, 2010
I am trying to create a stored procedure where I can insert null values in columns that have a foreign key constraint and allow nulls. The columns I am trying to insert nulls into are commentid and imageid. I have created an Insert statement in a stored procedure and I get the foreign key constraint error. Can you tell me how to allow inserting data in the other columns without having to insert anything in the commendid and the imageid?
Here is my exec of the stored procedure that is not working:
[Code]....
[Code]....
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Mar 18, 2011
I have a combobox within an edititem within a datalist:
<asp:DataList
runat="server"
DataKeyField="ChargeID"
ID="HistoryList"
DataSourceID="SqlDataSource1"
OnUpdateCommand="DataList1_UpdateCommand"
<EditItemTemplate>
<tr>
<td
width="70"
align="left">
[code]...
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Feb 11, 2010
Passing a null or nothing value to a datatime datatype database field (Access)
I've been all over the internet looking at this and I have tried dozens of methods without success.
I've read a few forums where, some say you can not assign a null value or a nothing value to a datetime datatype field. Then I see others where they say...'I got it to work'.
If this is true (that you can not pass a null value), how come I can create a record in the Access table and not assign a value to this date field? (The field is defined as not required).
Yet, once a value is in the field, I can not update that field back to a null or a nothing value.
So I'm hoping someone has the definitive answer to this.
I am using VB.Net Vs 2003 and updating an Access data base.
I have an update statement (see below) that uses parameters for updating.
what will work, so that I can put back the null or nothing value?
Or if it really can not be done, I guess I'll have to take that as truth.
[Code]....
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May 24, 2010
I use VS2005 on Oracle 10gR2. Using
(System.ComponentModel.DataObjectMethodType.Update,
True) to update database row that returns null values from date and numeric columns,Whenever i try to update same row with null (or empty) values on both date and numeric columns, it results in sending '01-Jan-0001' for date column and 0 for numeric column. I want the user to have the options of null or corresponding values for the update.
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Sep 13, 2010
1 - Is it necessary to have foreign key to obtain a Relation in Entity Framework between each entity.?
2 - I have a Language Table and many many table with a foreign key related to the language table. Is it right to add this foreign key or I should do something else ?
Ex:
Language
LangID
LangName
TableTextA
TblAID
TextInfo
LangID
TableTextB
TblBID
TextInfo
LangID
TableTextC
TblCID
TextInfo
LangID
etc ...
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Mar 5, 2010
I am updating a gridview. Problem is that when I hide certain fields that I do not want the user to update, they lose their values ie. the data is wiped out in the field unless I show them on the grid and make them writeable. Is there a property I need to set for the field to retain the value when the grid is updated or is this in the sql statement?
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Sep 17, 2010
So I sometimes use app_offline.htm to take an app offline while I upload a new version.However, while I am in the process of uploading larger dll's, I get the yellow error-screen saying the dll could not be loaded.This seems to be out of sync with my expectations of what app_offline.htm does (stops the app entirely), and also provides the users with errors in stead of the nice app_offline.htm I put up.Am I doing something wrong or is this behavior by design?
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Dec 6, 2010
I have setup my business object to have a create_date and edit_date members both datetime datatypes. My company want to display the create_date and edit_date fields in a gridview for each transaction. The problem i have is that after insterting a record it will have a valid create_date but no edit_date and when displayed in the gridview it defaults to datetime.minvalue (My default). How on earth do i show an empty field in my gridview for a null datetime field in the database?
I am using similar architecture to the Imar Spaanjaars example of a tiered solution. With a few small tweeks it has worked well for me for ages. I am passing a List<Database> to my object datasource which connects to my gridview.
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Mar 18, 2010
I have a problem with a SessionVariable. I will explain what is happening:
1. From the default.aspx I send Session["LoginByAdmin"] = "Dummy"; and then redirect to this page where I have the code below. So the Page_Load sees that this Session["LoginByAdmin"] != null and enter this page. This works fine !
2. In the Page_Load, I later fill a ListBox1 with foldernames.
3. With Button1_Click1, I will now delete the choosen Folder in the ListBox1 wich works fine the first time and the ListBox updates the new existing folders in the ListBox. (I have wrapped this inside an updatepanel)
The problems comes now when I try to delete a choosen folder in the ListBox1 the second time in a row. When I select a Folder in the ListBox1 and now Press Button1, I will be redirected to "Default.aspx". This meens that this code is running: (That meens that Session["LoginByAdmin"] == null and I have not set this to null anywhere. This is my big question how this variable can be = null here?
if (Session["LoginByAdmin"] == null)
Response.Redirect("Default.aspx");
break;
[Code]....
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Feb 24, 2010
I am using dropdownlist in my view page with some values which will display corresponding ID(primary key of other table) in my database.If i leave my dropdownlist blank and save it in database then its showing null parameter error. Can you explain how to use this reference type to overcome this error
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Aug 27, 2010
I want to use NHibernate with Asp.net 3.5 but i don't know how to use it.I search on Google but couldn't find the complete explanation about why to use NHibernate,Advantages of using it and integration with Asp.net projects.
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Jan 5, 2011
In my code behind, I have the following code that I want to insert a null value for a parameter. Instead of doing that, it is adding the word "NULL" to my database. What am I doing wrong?
dsRevealedByCR.UpdateParameters.Add("txtGrantor","Null")
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Aug 12, 2010
I am about to give up on this pos...unless somebody here simply gives me the right code to fix my problem. I'm tired of running in circles, and scouring the internet with no progress at all.
Problem: not updating collections with FK's.
Example:
Forum forum = new Forum("Sample");
category.AddForum(forum);
categoryRepository.Update(category); <- fails with transient object error for forum with no CategoryId.
Mapped right using References<Category> and HasMany<Forum>. Conventions are as follows.
Ref:
instance.Column(instance.Property.Name + "Id");
HasMany:
instance.Key.Column(instance.EntityType.Name + "Id");
instance.Cascade.All();
instance.Access.ReadOnlyPropertyThroughCamelCaseField(CamelCasePrefix.None);
Now, I've tried every possible setting for inverse, all the different cascades, on both sides. Nothing works. It just flat fails, telling me it can't insert NULL for Forum.CategoryId (field, not entity prop).
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Nov 12, 2010
I've been reading up on DDD a little bit, and I am confused how this would fit in when using an ORM like NHibernate. Right now I have a .NET MVC application with fairly "fat" controllers, and I'm trying to figure out how best to fix that. Moving this business logic into the model layer would be the best way to do this, but I am unsure how one would do that.
My application is set up so that NHibernate's session is managed by an HttpModule (gets session / transaction out of my way), which is used by repositories that return the entity objects (Think S#arp arch... turns out a really duplicated a lot of their functionality in this). These repositories are used by DataServices, which right now are just wrappers around the Repositories (one-to-one mapping between them, e.g. UserDataService takes a UserRepository, or actually a Repository). These DataServices right now only ensure that data annotations decorating the entity classes are checked when saving / updating.
In this way, my entities are really just data objects, but do not contain any real logic. While I could put some things in the entity classes (e.g. an "Approve" method), when that action needs to do something like sending an e-mail, or touching other non-related objects, or, for instance, checking to see if there are any users that have the same e-mail before approving, etc., then the entity would need access to other repositories, etc. Injecting these with an IoC wouldn't work with NHibernate, so you'd have to use a factory pattern I'm assuming to get these. I don't see how you would mock those in tests though......................
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Aug 10, 2010
I am using NHibernate in my web application. I need to use Convert() method in NHibernate query in order to get the date format as "MM/DD/YYYY".
I have used the below query using NHibernate query SELECT DISTINCT Convert(varchar(10),CurrentDate,101) AS Date FROM table order by Date desc.
But getting error.
Even I tried using views without unique key but Entity requires primary key.
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Feb 1, 2010
I am working on NHibernate with oracle in ASP.Net. Now i am trying TDD(Test Driven Development). Can you tell me the best way to develop the TDD for NHibernate with oracle?I am using MbUnit with microdesk but it is not better approach for oracle but SQL server.
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