ADO.NET :: Update DataContext's Table Implicitly In Linq Using 3.5?
Sep 7, 2010
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.
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'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
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.
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?
System.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:
[Code]....
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 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.
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?)
I have to find the best way to do this using LINQ. I need to summarize an amount in a iTransaction table by
Account (e.g. 12345) and add that amount to an same Account ( e.g12345) if it exists in a iAccount table . Here is the code which syntax checks ok and tested ok up to the .submitChanges statement (i.e. I stopped and didn't allow the submit.
Following is the LINQ code. (1) Is that a good way to do this. OR should I try the INTERCEPT.
(2) How is the best way to insert a new record/row in the iAccounts table if it DOES NOT exist in the iAccount Table.
I 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.
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 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()
If I have below code, how to make it work as it has below compile error:
Error: cannot implicitly convert type 'System.Linq.Iqueryable<system.data.DataSet> to 'System.Data.Dateset'. An explicit conversion exists.
public DataSet GetProductList() { using (var sdatabase = new DatabaseDataContext()) { IQueryable<DataSet> result = wmsdatabase.ExecuteQuery<DataSet>(@"SELECT productid, productname from product group by productid, productname").AsQueryable(); return result; // Compile error here } }
I have a System.Data.Linq.DataContext object and need to know the proper way of closing it out before it goes out of scope in order to prevent the following error when making a bunch of database changes:
Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached.
Can I just call obj.Dispose() or do I need to call obj.Connection.Dispose() or obj.Connection.Close()?
I guess what I want to know is will calling obj.Dispose() end up executing the functionality in obj.Connection.Dispose() and obj.Connection.Close(). The MSDN documentation that I found on these functions does not have this information (at least I didn't see it - I could have mistakenly overlooked it).
I have tables two tables, the "book" and the "author", a book can have many authors and vice versa, so there is an intermediate table called "book_author" with two columns as foreign key for those two primary keys
book_author book_id author_id
I'm trying to edit the book details and also its author using the entity date model, The controller class method
[Code]....
The HTML edit form
[Code]....
I can only update the book table, but not author that the book has or the book_author, I'm new to asp.net, I can't easily find a tutorial on this issue, I think the logic is to delete the author of the book first and then add the author for that book, but I don't know exactly about that linq and C# code. Can show me? I can only update the book table, but not author that the book has or the book_author, I'm new to asp.net, I can't easily find a tutorial on this issue, I think the logic is to delete the author of the book first and then add the author for that book, but I don't know exactly about that linq and C# code.
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 strange problem. I am adding a LinqDatasource object, and set the context:
[Code]....
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'.
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.
I've got a single table, with project information and schedule information. To make the data easier to present, I created a tab control with two panels (a detailsview in each). The first tab is for project info, the second tab is for schedule info (again, all fields in the same table). The problem is, if i change info in both tabs, and then hit the update button, only the data from one tab is added to the table. I think this problem is simple to fix, and boils down to the way I have the page organized, but I can't quite figure it out.
I've boiled my code down to the following conceptualized structure:
[code]....
When you click the update button, you return to the listview, but with only the information from your current tab saved. How can I get it to update from both detailsviews?
I'm sure this has been answered many times already, but I still can't seem to find exactly how to search for this issue, so apologies in advance.
Anyway, I have a VB script for entering a row of data into a table by a web user. When this row of data is entered, I wish to take some of the values from the columns of the "primary" table, and have that data automatically create a new row of data in a "secondary" table. I think I'm part of the way there, here is my script:
[code]...
"ProductsByMfr" is the "primary" table - the table that the user adds data into when the button click event is fired.
"DealerPricing" is a "secondary" table that I wish to have some of the data from the newly-entered row in ProductsByMfr copied into. Am I even close here?
I'm using the ASP.Net Membership provider, but I don't want to allow system administrators to DELETE any users. Instead, I simply want to mark them as locked out (aspnet_Membership.IsLockedOut) of the system so they can't log in when an administrator assigns them to a role titled "Inactive". Make sense? Right now my trigger isn't throwing any errors, but it's not working either. Here's my trigger (which is on the aspnet_UsersInRoles table):
I am trying to delete or add rows in a table but since the table is in an update panel,upon deletion the row goes away and then comes back.I have tried using return false but it does not seem to work in IE or FF.
