I'm studing Linq on TheBeerHouse Project,I would create a my Linq Version.I have a big problem with Updating, this i a part of source :
protected static ArticlesDataContext GetContext()
{
return new ArticlesDataContext(Settings.ConnectionString);
[code]...
I have a linq DataSource and a Grid in my htnl and I want to access the DataContext from code behind. Now in the past when I do evrything in code behind I just use...
DataContextName db = new DataContextName();
and I have my reference.
Now I can still do that and it works fine it just seems odd to be making a second class object when there is one that is made from the linq DataSource in the html. But I can't figure out how to get a reference to the DataContext that is created from my html code.
What's wrong with the following code?
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After the SubmitChanges call, the Text field in data2 wasn't changed. According to the NerdDinner sample, I supposedly can just write to my data object and then call SubmitChanges.
I want to create a LINQ DataContext Class as per Database Design. I getting a problem in some cases.
the syntax to bulid a LINQ class :
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Here Table Name Is HardCoded But I my case my Table Name A Changed as Finicial Year Change.So How I Give The TableName As RunTime
I have a strange problem. I am adding a LinqDatasource object, and set the context:
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Then I get this error:The type 'System.Data.Linq.DataContext' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Data.Linq, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'.
On web.config I already have this:
<add assembly="System.Data.Linq, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"/>
NOTE: The datacontext is in a different project (DLL proect) where I added a refernce to System.Data.Linq.
is there another way adding a refernce to a web project? or only though teh web.config?
i am working on Linq,as we know to use any table in linq we have to drag and drop it on our datacontext's Designer File,and at run time we got its value,till here no any problem,main point is if any changes in respective data source's schema has made ,then on datacontext we will not get that changes,for it we have to change this datacontext manually by by again drag and drop,it will not happen implicitly when this changes has been made on the data source. how i solve this problem so that datacontext change implicitly without any over head using .net 3.5.
View 2 RepliesI am running the folowing simple test code:
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But the UpdateUser field does not update - it remains at NULL. No errors occur. I can use similar code to update table fields in other dbmls successfully.
I have a method to execute two "Update" sql statements.
The first one works fine and the second one I can't get to work for nothing.
Here is the entire method:
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The error I am getting is "Incorrect syntax near '05'."
It is occuring on the next to the last line which is:
dc.ExecuteCommand(sql);
I update the variable "sql" first so I can debug. At the time it crashes the value of sql is:
"Update Blogs set Status = 'Archived', ArchiveDate = 06/22/2010 05:14:46 PM Where (BlogID != 1) and (Status = 'Published') and (AuthorID = 9e37e028-c205-4903-920e-e8643b30a724)"
It appears to be the ArchiveDate that is causing the problem here. The "05" is the hour of the time portion. Both ArcgiveDate and PublishDate are defined exactly the same in the database. If you look at the first dc.ExecuteCommand it does exactly the same
thing with PublishDate (DateTime column) in the same table and it works just fine.
Then I modifed the code and remove the ArchiveDate from the sql statement then I get the error:
"Incorrect syntax near 'e028'."
which as you can see is part of the AuthorIDs value in the where clause. So I am assuming both the date and the Guid / Author ID is causing problems. I have tried enclosing the values in quotes but I just cant make this work even though it seems to be working fine in other places.
I even remove the code for the author ID and left in the code for the ArchiveDate and it still does not work so I have proved that both are causing a problem.
I have a table with Id, Name,...IsActive, etc. If user wants to delete a record from the user, he/she should update the field IsActive to false. I am able to acheive this functionality using the below steps,
1. Query the database for the row which is to be updated.
2. Update the property IsActive to false.
3. Submit the changes to the database.
This way i am successful. But i have a query here is that, when we execute steps 1 and 3, there will be two trips to the database for getting the required object and again updating the same object to the database.
Is this not a performance hit having multiple calls to DB for a simple operation.?
Do we have any other go, where in within a single call to database, can i update a field of row?
I'm trying to use linq to sql for my project (very short deadline), and I'm kind of in a bind. I don't know the best way to have a data context handy per request thread. I want something like a singleton class from which all my repository classes can access the current data context. However, singleton class is static and is not thread-safe and therefore not suitable for web apps. I want something that would create a data context at the beginning of the request and dispose of it along with the request
View 1 RepliesI am using Linq to SQL. Tables have timestamp columns and I am using regular Linq methodology in ASP.NET MVC.I do use detached entities and always try to do updates without first querying the database for the original entity. To update an entity I use context.Attach(entity, true) followed by context.SubmitChanges() and all is fine. The sql statement that gets executed looks like:
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For no apparent reason (of course there must be one), my web project will no longer generate LINQ to SQL classes/data contexts!!!I am going about the usual routine of right clicking the project, adding new item, selected LINQ to SQL classes, then dragging over a table from Server Explorer, saving and build but no...the bloody thing won't appear!!!Does anyone know why this might be happening/what have I done wrong?
View 1 RepliesI have 2 databases one called DB1, and the other DB2. Both of them has exactly the same design (tables, procedures and etc..)
Now, I am using SQLMETAL to create the DataContext. problem is that there are two lines that direct to a certain database and so I cannot use the same code for both databases.
here is the code:
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Now, What I am lookin for is a programmatically way to change this two lines (DataBaseAttribute and the connrection string) .
The easiest solution for me of course is to create the class twice, with the same code and just change manually what I need which is not what I am looking for.
There is a full discussion with microsoft stuff right here: [URL]
cannot create datacontext for make a select
View 2 RepliesI like to use my own stored procs as much as possible.
That way I know exactly what's happening and I can explain and control things.
I'm using stored procs with LINQ to SQL for CRUD operations.
For select, insert and delete - using stored procs with LINQ to SQL is pretty straightforward.
However, if I want to use my own custom stored procs with L2S for updates what's the best way to accomplish this?
Can you provide some code that shows the best approach that you would personally choose for this?
I have a form that gets populated by LINQ and I want to be able to update the database using that same form. The form is populated by grabbing a querystring (for example, "edit=10") and searching the primary key for that record. So far so good. I have a button attached to the function below which is supposed to use LINQ to update the database with data from the form. I get no errors, but for some reason, it is only updating one field (Last_Updated) instead of all of them.
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i want to update many rows with difference values inside table. i'm coding a timetable.
View 3 RepliesSystem.Data.Linq.ChangeConflictException: 2 of X updates failed. at System.Data.Linq.ChangeProcessor.SubmitChanges(ConflictMode failureMode) at System.Data.Linq.DataContext.SubmitChanges(ConflictMode failureMode) at PROJECT.Controllers.HomeController.ClickProc(Int32
id, String code, String n)
This is what I get very often. This action is done thousands of times a day, and I get this exception about once every 5 seconds. From what I understand it happens when something changes in the database in the period between creating DataContext and updating it. Am I right?How can I fix it?I just debugged the error and found the following:
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The Stats table is updated constantly. So how can I still make LINQsave the changes. With "classical" MS SQL access through SqlDataCommand I never had problems like that.
I am trying to return all records from a table using a Linq strongly typed datacontext. I want this in its own dll and accessible via a public method. I am basing this on the following MSDN example:
[URL]
I get no intellisense for appt in the Linq code and I also get a compile error for Table<Appointments>:
The type or namespace name 'Appointments' could not be found (are you missing a using directive or an assembly reference?)
Here is my code:
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I am trying to update my table ARTICLES and it has a field COUNTER, Everytime a user enter this ARTICLES, the page_load event runs a LINQ to SQL query taking the QueryString as parameter, increasing the COUNTER field in 1.
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I am creating a database frontend in aspx/C# using LINQ to MSSQL. It has two pages: a main page which lists all of the records, and a page that appears when the user click the "Edit" button next to one of the list items for the user to edit a record.The database table has about 70 user-editable fields. I need to make the edit page, allowing the user to update/insert records. There are a couple ways I can think of make an edit page:Using a LinqDataSource and FormViewUsing a LinqDataSource and DetailsViewManually retrieve the value for each field and set the value for each field directly from Linq (e.g. "projectIDLabel.Text = Convert.ToString(thisRecord.Project_ID)"What would be the best way to design this?
View 4 RepliesI am writing an application in C# that uses LINQ to validate a datacontext off a textbox to see if the record exists already. If the record does exist I inserted an if statement to advise the user that the record exists, if the record does not exist I would like to allow the record to be added to the database. If I take out my else statement everything works fine as far as inserting goes, but I do not want to allow inserts in this scenario. I have tried moving the if and else statement to different parts of the code but can't quite figure this one out.
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I need my linq to sql datacontext to be available across my business/data layer for all my repository objects to access. However since this is a web app, I want to create and destroy it per request. I'm wondering if having a singleton class that can lazily create and attach the datacontext to current HttpContext would work. My question is: would the datacontext get disposed automatically when the request ends? Below is the code for what I'm thinking. Would this accomplish my purpose: have a thread-safe datacontext instance that is lazily available and is automatically disposed when the request ends?
public class SingletonDC
{
public static NorthwindDataContext Default
{
get
{
NorthwindDataContext defaultInstance = (NorthwindDataContext)System.Web.HttpContext.Current.Items["datacontext"];
if (defaultInstance == null)
{
defaultInstance = new NorthwindDataContext();
System.Web.HttpContext.Current.Items.Add("datacontext", defaultInstance);
}
return defaultInstance;
}
}
}
I'm new to LINQ and have a problem with my query not showing me the Table Collection. I manually created my Cart class and specified the table attributes on each property (works fine for inserting records via LINQ see below). DataContext dc = new DataContext(Conn);
var q = (from c in dc.NOTABLES?? where ((c.UserID == userID)) orderby c.CreateDateTime Based on examples I would expect to see dc.Cart But I don't, so I tried to access it via dc.GetTable<Cart>() which at least gets me data but doesn't seem to convert the rows to my Cart object since this:
foreach (var cart in q) Log.Info("UserID: " + cart.UserID + " CartID: " + cart.ID.ToString());
blows up with a "Specified Cast is Not Valid" exception.
No Problem Inserting Also, I had no problem inserting data into the database:
DataContext dc = new DataContext(Conn);
Table<Cart> Carts = dc.GetTable<Cart>();
Cart aCart = new Cart();
aCart.UserID = userId;
aCart.Description = description;
aCart.CreateDateTime = System.DateTime.Now;
aCart.UpdateDateTime = System.DateTime.Now;
Carts.InsertOnSubmit(aCart);
Carts.Context.SubmitChanges();
I am trying to run a linq query but I need the result as a datatable as I am using that to store records from different queries in the same viewstate object.The 2 versions below compile, but return an empty set. The exact error is "Value cannot be null.Parameter name: source". (and yes I have checked there is data):
MyDatabaseDataContext db = new MyDatabaseDataContext(conn);
IEnumerable<DataRow> queryProjects =
(from DataRow p in db.STREAM_PROJECTs.AsEnumerable()
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