Web Forms :: LINQtoSQL DataContext In Web Application ?
Jun 25, 2010
I'm running Visual Web Developer 2010 Express on Windows XP and I'm having some trouble linking my DataContext to a control.If I create a new "Web Site", add a new LINQ to SQL Class and add the database tables I want, then add a Control such as FormView and choose a new LINQ Data Source Type; my DataContext I created is visible in the list and all work OK.If I do the same after creating a new "Web Application", my DataContext doesn't show up in the list, but if I go into my Code Behind I can access my DataContext through:
Dim db = new ForumDataContext()
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Mar 20, 2010
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
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Jun 1, 2010
I have the Global.asax like the code below:
public class MvcApplication : System.Web.HttpApplication
{
public static void RegisterRoutes(RouteCollection routes)
[code]...
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May 14, 2010
Dim newMem As New Subscription With { _
.First = txtName.Text, _
.Email = txtEmail.Text, _
.dateLastEmail = "1/1/1980", _
.subDate = Now}
dbp.Subscriptions.InsertOnSubmit(newMem)
dbp.SubmitChanges()
The table contains a field called conDate that is nullable, and in this case I want it to remain null. It will get a date value later, when a confirmation is received. If I add .conDate = "1/1/1980", _ I can successfully add the record, but without that line I get System.InvalidOperationException: Nullable object must have a value. I tried this:
Dim DateConfirm As System.Nullable(Of DateTime) = Nothing and adding
.conDate = DateConfirm, _ but that didn't help either. How can I add a record without giving a date to a field I want to remain null?
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Feb 3, 2010
I have some datatables in a LinqToSql entity model (edmx) that are structured like this: SalesOpportunity *<-1 User *<-1 Person i.e Many SalesOpportunities / 1 User, Many Users / 1 Person Anyway, My DomainService is SalesOpportunity centric, and I want to serialize info about the person into the metadata class. I can serialize data about the user without any problem like this:
MetaData Class:
<Include("UserName", "UserName")> _
Public User As User
DomainService Class - GetOpportunities()
Return Me.ObjectContext.Opportunities.Include("User")
I've been trying for several hours to get the Person information. If you have any tips, I'd be grateful to hear them.
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Feb 23, 2010
Here's my problem: I have an IPerson which is implemented by Employee and Student. What I really want is what you see below. One LINQ statement to get each type of IPerson. This works great until I call the method ;). It makes sense as to why I'd get the error, but I am really struggling as to find a decent way to pull all IPerson objects from the DB and avoid putting switch statements all over my application.
[code]....
Above, there is a commented out return statement - that essentially does a .ToList() and forgoes the whole deferred execution thing, creating 2 SQL statements - not ideal.
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Sep 9, 2010
I'm trying to create a self referencing object using linqTOsql mapping. So far, I am definitely in over my head. Here's the code I have:
[Table]
public class Category
{
[Column(IsPrimaryKey=true, IsDbGenerated=true, AutoSync=AutoSync.OnInsert)]
public Int64 catID { get; set; }
public Int64 parentCatID { get; set; }
[code]...
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Mar 17, 2011
I have a store procedure as below:
using(DataStoreContext ctx = new DataStoreContext())
{
int value = ctx.RequestProc(filename, message).First().Result;
}
I would like to create Asynchronus access to database to execute this above procedure, where I am using LinqToSql.
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Jun 1, 2010
I need to create a .XLS file and put it available for download in my .aspx page. this file is needed to have information from database. I'm using Linq to SQL. So I need a C# code for reading from DataBase using Linq and create a .XLS file for download.
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Mar 22, 2010
I am probably doing this wrong but I want to take all words entered in to a text box and return all records that contain any or all of the words. Can any one point me in the right direction?
protected void ldsGvFaqs_Selecting(object sender, LinqDataSourceSelectEventArgs e)
{
if (txbSearch.Text.Length > 0)
{
string temp = string.Empty;
string[] words = txbSearch.Text.Split(' ');
int counter = words.Length;
foreach (var word in words)
{
temp += "Tags.Contains('" + word + "')";
counter -= 1;
if (counter > 0)
{
temp += " || ";
}
}
ldsGvFaqs.Where = temp;
}
}
But I get the following error, Character literal must contain exactly one character.
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Aug 3, 2010
I have a bunch of tables which are related in various ways, and I drag and drop them into the MSLinqToSQLGenerator, then save etc. But theres a couple tables and a few columns from other tables that don't get recognized in my code, despite repeated regenerations and trying to create a whole new file, it keeps telling me the fields dont exist when I try to use them, meanwhile I'm using other values from the same tables(the ones that where values are missing from) just fine... The Missing tables are defined in the generated classes, as are the values along with property functions... I'm not using any custom tools either... just straight ms visual web developer 2010 express...
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Mar 15, 2010
I'm using MVC 2 with some Models from a LinqToSql project that I built. I see that when I post back to a Controller Action after editing a form that has a DateTime field from the Model, the MVC Html.ValidationMessageFor() helper will nicely display an error beside the Date text box. This seems to happen automatically when the you test ModelState.IsValid() in the Controller Action, as if the MVC model binding automatically knows that the DateTime field cannot be empty.
My question is... I have some other string fields in these LinqToSql generated classes that are Not-Nullable (marked as Not Nullable in Sql Server which passes thourgh to the LinqToSql generated classes), so why doesn't Mr. MVC pick up on those as well and display a "Required" message in the ValidationMessageFor() placeholders I have added for those fields?
Sure, I have successfully added the MetadataType(typeof<t>) buddy classes to cover these Non-nullable string fields, but it sure does seem redundant to add all this metadata in buddy classes when the LinqToSql generated classes already contain enough info that MVC could sniff out. It MVC validation works with DateTime automatically, why not these Not-nullable fields too?
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Oct 5, 2010
This is my first attempt at updating a database using LINQtoSQL. At least, it's my first if you don't count the tutorials I've followed. Unfortunately, The tutorials that I have found don't offer much more than updating a single table. I'm attempting to update a DB Model that's a bit more complex.
I have a Stream table:
[Code]....
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Apr 4, 2011
DataContext db = new DataContext(conString);
var dvd = db.GetTable<DvdList>();
var category = db.GetTable<CategoryList>();
var query= from b in dvd
join category on dvd.CategoryId equals category.CategoryId
where b.Title.Contains(txtSearch.Text)
select b;
GridView1.DataSource =query;
here has error "join category on dvd"
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Nov 13, 2010
i am using MVC for my project in the logon authentication, when i login using correct values there is no problem.
If i login using false or empty values i get the DataContext accessed after Dispose error.
i get it in the first line itself 'using (HealthObjectDataContext dc = DataContextFactory.GetDataContext())'
this is the method i use in the security service.
[code]....
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Feb 12, 2010
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?
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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.
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Jan 8, 2010
I am using LINQ to SQL in a project. I create a new DataContext class (a "DBML").
This is a DotNetNuke portal, module project. DNN has a standard connection string named "SiteSQLServer." Of course, I want my DataContext class to use this same connection string.
In Server Explorer in Visual Studio, I have a connection to the development database. Of course, that connection knows nothing of the "SiteSQLServer" connection string in web.config.
When I drag a table into the DBML design screen, I get a popup message that the table I'm dragging in is from a different connection, and is it OK if it changes the connection string? If I say "No," then the table never comes in to the designer. If I say "OK," then Visual Studio adds a new connection string to my web.config file. Then I must click in the open area of the designer, then go to the Properties window and reset the connection string. If I miss this, then in testing everything works. But when I deploy to a production server, the connection fails. But even if I do not miss this, that extra connection string remains in my web.config file.
Is there a way to get Visual Studio to drop the table into the designer, and leave web.config alone?
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Mar 26, 2010
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.
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Jan 21, 2010
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.
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Mar 5, 2011
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:
[Code]....
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Mar 30, 2010
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]...
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Aug 20, 2010
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.
[Code]....
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Apr 17, 2010
I 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:
[Code]....
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]
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Mar 20, 2010
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;
}
}
}
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