C# - Fastest Way To Fill DataTable From LINQ Query Using DataContext?
Feb 10, 2011
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()
[code]...
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Aug 13, 2010
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();
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May 10, 2010
using linqs how to fill datatable using linq to sql in asp.net
i have one storedprocedure to select data from table
and one s.p for insert the data and one for update the data
how i use these s.p to insert and update the data using linq. to sql
I am gettin error in this code
[Code]....
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Mar 14, 2010
'm not sure if this is the right forum, but I couldnt find one for linq related questions.I have the following problem. I have four tables, One with users, one with projects, one with the users and the projects they are in (joinProjectTable) and on table where the users can fill in there worked hours for a certain project. These hours are filled in on a daily base. Now every month there is going to be created a report on the workedHours table so there is visible which user has entered how many hours for a certain project. On this report there is gonna be a billing for the company where for the hours are worked. This is the easy part, the hard part is the following.
companies also want to have a list of users that didn't entered any hours for that particular month for a particular project. So I have to write a linq query that would look in the joinprojecttable to see which users are joined to which projects, and than with that join it should look if that particular combination (user+project) is in anyway entered in the workedhourstable for that particular month. If not this has to be shown in the datagrid, for every user that isnt in the workedhourstable for that month. So it should be a certain NOT query, but I can't seem to figure it out.does anyone have any idea to accomplisch this in Linq2Sql? I'm using VB instead of C#.
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Feb 23, 2011
how to convert a linq query to a datatable
this is my query
[Code]....
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Jun 13, 2010
how to extract DataTable or DataSet from Linq Query or List. e.g I have linq query like this
MyDBpDataContext dcSp = new MyDBpDataContext();
dcSp.myProgrammSP().ToList();
I wrote an Sp which sends a Table as result and I have code which is already using DataTable So I want to convert this result in DataTable.
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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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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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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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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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Apr 1, 2011
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).
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May 5, 2010
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 :
[Code]....
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
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May 28, 2010
I'm looking to translate an SQL query into linq
INNER JOIN Usrs ON
SAQ.UserId =
Usrs.UserId AND Scan.UserId =
Users.UserId
I'm not sure how to include the "AND" in the LINQ statement.
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May 28, 2010
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'.
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?
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Feb 7, 2011
I am trying to use a SqlDataAdapter to fill a DataTable, which I use as a data source to a DataGrid. The query is fine, at least when I run it manually in SSMSE. When I do the fill operation, the table gets the right columns, but no rows. The most frustrating part of this is that the code is identical (with a different query) on a different page. I cannot post the query, but my initialization code looks like this:
SqlCommand areaDAC = new SqlCommand (areaQuery, connection);
areaDAC.Parameters.Add (new SqlParameter ("@param", System.Data.SqlDbType.NVarChar, 50));
m_areaDataAdapter = new SqlDataAdapter (areaDAC);
Then to use it:
m_areaDataAdapter.SelectCommand.Parameters["@param"].Value = "Filter Val";
DataTable table = new DataTable ();
m_areaDataAdapter.Fill (table);
At this point, table has the right number of columns and no rows. I know the parameters are being added correctly, I know that data exists for the given query.
Update (as provided by Nik in a comment):
[Code]....
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Dec 1, 2010
I have a dataset with a table adapter that has several queries. I want to execute on of the queries and fill a data table but am having trouble with this operation. Am I invoking my table adapter incorrectly? See line 56.
[Code]....
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Mar 11, 2011
I tried to use typed dataset with a simple query and i got the report working.
Now, i am trying to do is:
I made a class in a project. That class just contains a simple function with a select query. This query returns a datatable. I just want to use all the fields returned by the datatable in the report.
Is there any solution to this ? or my approach is wrong ?
[Code]....
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Jan 26, 2011
Using C#, Visual Studio 2010
I have 8 drop downlists created in .aspx page.
I try to programmatically fill the 8 using a single datatable. Each dropdownlist has its own column in the datatable and is supposed to display only the column that corresponds to it. It does display the column it is supposed to however it also displays a number of empty slots equal to all the other columns combined.Here is the code can someone tell me why I get the empty slots?
[Code]....
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Jun 8, 2010
In am using following code for paging purpose in asp.net to reduce the load of reading all the records from the database.
SqlDataAdapter.Fill(StartRecord,MaxRecords, DataTable);
I want to know whether this code Get all data from data base and filter the records in application or just fetch the needed records only.
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Aug 20, 2010
I trying to fill dataset using LINQ for past 2 days, I could not able to make it.
This is my query.
[Code]....
How can i fill the dataset,make use of above query.
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