C# - LinqToSql - Prevent Sub Queries When Limiting Number Of Rows Returned?
Sep 16, 2009
Dim query = (From p in Parent _
select _
p.ID, _
Tags = String.Join("|", p.Child.Select(Function(c) c.Tag.TagName).ToArray)).Take(100)
In the above query, when using Take to limit the rows returned, a separate SQL query is executed for each row to return the 'Tags' field. If I remove Take(100), a single query to sent to Sql Server.So, how do I limit the number of rows returned, while preventing a new sub query being executed for each row?
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Jun 18, 2010
After connecting to a database using DataReader, how can I count the number of rows ?
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Sep 6, 2009
I had a DataGridView in which i want to fetch the data from the access database,so i did this
Dim connString As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=Etech.mdb"
Dim myConnection As OleDbConnection = New OleDbConnection
myConnection.ConnectionString = connString
[Code]...
In the above snapshot,after fetching the data from the access database to the DataGridView,i want to remove the PplicyHolderName,PremiumAmount and a few other columns since these are the columns which do not contain any data....
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May 19, 2011
Does anyone know how to add a limit to the number of items in a list box? For example, you can't add more than 10 items in ListBox1.
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Oct 15, 2011
how can i limit a user to enter 10 digit no like telephone no in textbox without using regular expressions?
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Oct 9, 2011
how can i limit a user to enter just 10 digit number (minimum 8 but not more than that 10 in any case) in a textbox(like telephone no)?
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Jun 2, 2012
I am creating an application in Visual Basic '08 with four available checkboxes. Is it possible to limit the number of checkboxes you may select down to 2, and how may I go about doing this?
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Apr 9, 2010
I need to retrieve multiple objects from an external system. The external system supports multiple simultaneous requests (i.e. threads), but it is possible to flood the external system - therefore I want to be able to retrieve multiple objects asynchronously, but I want to be able to throttle the number of simultaneous async requests. i.e. I need to retrieve 100 items, but don't want to be retrieving more than 25 of them at once. When each request of the 25 completes, I want to trigger another retrieval, and once they are all complete I want to return all of the results in the order they were requested (i.e. there is no point returning the results until the entire call is returned). Are there any recommended patterns for this sort of thing?
[Code]...
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Jan 28, 2012
Assuming that I have a Windows Forms textbox and want to reduce the maximum amount of characters that can be allowed in via user entry, how would I do that?
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Aug 11, 2011
I have a model that returns a dataset to a view and builds a list. The crazy thing is that I have tested this code with IE, Safari on Mac and Windows, Chrome and Opera and all return data. However, on the iPad or iPhone, zero rows are returned from the dataset object. It seems that the model is in fact passing the dataset to the view. I am using jquerymobile to render the view for the iOS devices and have taken that out of the mix to test and it still doesn't work.
[Code]...
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Sep 24, 2010
I'd like to know after I've executed MySqlReder = MySqlCommand.ExecuteReader() how many rows it returned. If it's one I can continue processing with the data. If it's more than one I need to populate a drop down list box.
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Jun 23, 2009
I am currently writing unit tests for an application near completion (before management looks at it and turns it inside out). I am testing the business layer and a method is set to return a datatable of all "GroupID"s, which are simply an integer to represent the group that a user belongs to.
I'm assuming the best way to assert on this unit test would be to assert that the correct groupIDs are being returned from a controlled test database. However, I'm not sure how to assert on a datatable. Is the only (and best) possible way to accomplish this to simply loop through the datatable until it's empty and add each value to an array of integers? How would one go about asserting on this test?
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Feb 6, 2011
When I query a DataTable using LINQ, are the rows returned as references? Either way, is it possible to control this behaviour, so that rows are either returned as references or as new rows?My guess is that all objects are returned as references by default, since that seems to be the normal behaviour in most programming languages.
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Jul 27, 2010
when populating a data grid i keep getting a redundant row in the bottom. is there a way to lock grid rows to the number of rows in the data table?
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Jan 18, 2012
I am currently using DevExpress 10.2 within Visual Studio 2010. In a previous question I was trying to print the current user view of a DevExpress GridControl with the user's choice of expanded or collapsed master rows and/or group sections. I was told this was not possible at this time. I have now decided to use the following code:
[Code]...
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Apr 21, 2009
I'm trying to access the Count Property on the array of rows returned by the datatables select method, this is after converting the Web Project to 3.5
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Jan 23, 2006
I have been playing around with datareader for a little while, and I can't figure out how to get the number of row returned? [code]...
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Mar 17, 2011
Here's my
Module Module1
Dim Board(3, 3) As Char
Dim PlayerOneName As String
Dim PlayerTwoName As String
Dim PlayerOneScore As Single
[Code] .....
How can I make it come up with no error when no coordinate has been entered, basically instead of a number being enter, the return key is just pressed.
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Feb 1, 2012
I have an application that reads the output from a process running the "Net View" command. How can I determine the number of lines returned by the process so that I can dynamically set the upper bound of a "For Next" statement?
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Jan 8, 2012
how do i count the number of rows that are affected when I updated a table, and display the number of affected rows in a message box ??
here is my code for updating the table ...
For Each row As DataGridViewRow In DataGridView1.Rows
req = row.Cells(Column1.Name).Value
If row.Cells("Column1").Value = True Then
[Code].....
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Apr 19, 2009
Im wondering, whats the code for looking up and preventing a number from being submited into, say a textbox?
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Jan 6, 2010
I am writing a message system on my server, the xml is something like this
<xml>
<entry>
<sender>[code]....
my problem now i guess is 2 fold, i wish to combine the first 3 queries into a single query and place in a list or a collection or is there a way to do this with a single query that will give me my desired result?
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Sep 11, 2011
what is code that prevent user to given number less than 8 in the text box. If the user give less then 8 number then message box box will appear which show Minimum Number is 8. Here is my code
Private Sub btnregister_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnregister.Click
If TELEPHONETextBox.Text.Trim.Length = 0 Then
MsgBox("Please Enter Phone Number", MsgBoxStyle.Question)
Me.TELEPHONETextBox.Focus()
[code].....
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Feb 23, 2012
I'm going to use an existing query on an SQLCE database on Windows Phone. From what I understand, the only way to access a local db is via Linq2Sql.So, your challenge, if you choose to accept it, is to convert this fairly complicated query to Linq. I have doubts whether the linq driver is smart enough to use the exists functions.The inserts are for context only, to give you an idea of the db structure
DECLARE @OrderProducts TABLE(OrderID INT, ProductID INT);
DECLARE @Products TABLE(ProductID INT, ProductName VARCHAR(32));
INSERT @Products VALUES
[code]....
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Aug 19, 2010
Here is the code:
Function getData(ByVal id As String)
Dim reader As SqlClient.SqlDataReader
Dim statement As String
[code].....
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Oct 28, 2011
I wonder if somebody could point me in the right direction. I've recently started playing with LinqToSQL and love the strongly typed data objects etc.I'm just struggling to understand the impact on database performance etc. For example, say I was developing a simple user profile page. The page shows basic information about the user, some information on their recent activity, and a list of unread notifications.
If I was developing a stored procedure for this page, I could create a single SP which returns multiple datatables covering all of the required information - resulting in a single db call.
However, using LinqToSQL, this could results in many calls - one for user info, atleast one for activity, atleast one for notifications, if I then want further info on notifications this may result in further calls - multiple db calls.
Should I be worried about the number of db calls happenning as a result of using this design pattern? Ie, are the multiple db handshakes etc going to degrade my db etc?
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Sep 14, 2010
I'm using LinqToSql to talk to my database. It's working great but I would like to know if there are pending changes. I know how to endedit() and submitchanges() on the underlying context. But is there a property that will tell me if changes have been made? I've looked through the properties and methods of both the bindingsource object and the datacontext but nothing is popping out at me.
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Jul 26, 2010
Is it possible to number the rows in DataGridView ( does this property exist)?
When I load the data from the database to DataGridView I want to show thenumbers of row. like this
0
1
2
3
.
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Nov 2, 2009
I have a DataGridView.datasource bound to LinkToSql. I fill the data based on a sequence number. If the sequence number is not part of the the data, I will need to add a record. This should be easy and make sence, but it would appear, at least to me to be a bit more difficult.The grid will not add a new record if the LinqToSql query is empty
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May 10, 2012
I have a VB report which contains a list of locations. I have this list separated into areas and I need to count the total number of rows per area section. I have a groupHeader which contains my area field, then in the group I list the corresponding entries for that area. Then in the groupFooter I would like to give the total number of entries in the group. How can I do this? I have two fields in my groupFooter
groupCount
groupTotalAmount
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