I have a Form1 with a query, and I want to display the results in a DataGridView in Form2, like this:
Form1:
VB
Dim Db As New DataClasses1DataContext
Dim Qry = From country In Db.Countries
Select country
[Code]....
I know that LINQ queries are deferred and only executed when the query is enumerated, but I'm having trouble figuring out exactly when that happens.Certainly in a For Each loop, the query would be enumerated.What's the rule of thumb to follow? I don't want to accidentally enumerate over my query twice if it's a huge result.
For example, does System.Linq.Enumerable.First enumerate over the whole query? I ask for performance reasons. I want to pass a LINQ result set to an ASP.NET MVC view, and I also want to pass the First element separately. Enumerating over the results twice would be painful.It would be great to turn on some kind of flag that alerts me each time a LINQ query is enumerated. That way I could catch scenarios when I accidentally enumerate twice.
I have a form with a tab control, containing a small number of tab pages. I'm writing a sub procedure to clear the controls within a groupbox for the selected tab. A selected tab will only ever contain ONE groupbox and within a groupbox will be command buttons, labels, text boxes and possibly a combobox. The first block of code below firstly finds the groupbox within the selected tab. The next part loops around all control type and if of type texbox clears the text.
Now hears the head scratcher/confusion it error's with :-
Unable to cast object of type 'System.Windows.Forms.Button' to type 'System.Windows.Forms.GroupBox
Which I don't understand as I cant see where Im converting objects simply looping through all controls and then ONLY if type of control is textbox then clear text.
'Loop around all controls in form, simplified that all controls
'are within a SINGLE groupbox and clear contents or reset to default value
Dim groupbox = (From grpbx In tabAdmin.SelectedTab.Controls _
Select grpbx = DirectCast(grpbx, GroupBox) _
Where TypeOf grpbx Is GroupBox)
[Code] .....
I am trying to run a query an Access db from VB. The general query which I want to run is
SELECT * FROM Patient WHERE Patient.PatientID = ?
or SELECT * FROM Patient WHERE Patient.PatientLname = ?
I tried using an input box which captured the user input and pass that variable to the query, but that failed. Then I read about writing a function and using that, however, I keep getting an error which says Function not defined, but when stepping through the code, it seems to work. Here is my function: [Code]
given this function:
Public Function Search(ByVal StartIndex As Integer, _
ByVal MaxResults As Integer, _
ByVal AccountNumber As String, _
ByVal LastName As String, _
[Code]....
instead of what I expected:
Select count(*) from remitline where lastname = "smith"
What am I doing wrong building up the where clause? I'm using Castle ActiveRecord 2.1
if there is that much of a performance gain in running a LINQ stored procedure versus a LINQ query?
View 1 RepliesI have to join two main tables, and I need to filter the results by elements in an ASP.NET web form. These filters are created on the fly so I have to use a lot of where extensions to filter the query. I want to execute the query with as optimized SQL as possible.
I am first doing a simple join between TW_Sites and TW_Investigators. Then there are two sub-tables that are involved. TW_InvestigatorToArea and TW_InvestigatorToDisease. While most of the where clauses are working fine, I have found a performance issue that won't be an issue right now, but will be an issue as the table gets bigger.
The arrays DiseaseCategories and DiseaseAreas would be the results of a CheckBoxList result.
Protected Sub LoadResults()
'Get Dictionary of Filters
Dim FilterDictionary As OrderedDictionary = Session.Item("InvestigatorFilterDictionary")
' Initialize LinqToSql
[code]....
Forgive my ignorance on this.I have this LINQ Query:Dim ngBikersDataContext As New CarBikeWalkDataContext
bikersList = (From c In ngBikersDataContext.Reg_Bikers _
Order By c.L_Name _
Select New Bikers() With { _
.BikerID = c.BikerID, _
.F_Name = c.F_Name, _
[Code]...
with the error "Overload resolution failed because no accesible 'Select' accepts this number of arguments."
Over the "NEW" I get an error " ')'expected."
We are doing a query against an in-memory collection of LINQ data objects. The wrinkle is that we are ordering by a column in a related table whose records have not necessarily been loaded yet (deferred loading:)
Dim oPkgProducts = _
From b In oBillPkg.BillProducts _
Where b.Successful.GetValueOrDefault(Common.X_INDETERMINATE) = _
[code]....
How do I add ROW_NUMBER to a LINQ query or Entity? How can I convert this solution to VB.NET?
[Code]...
I'm having trouble porting that last line. I have been unable to locate a VB.NET example. I'm actually not looking for any paging functionality like the example provides, just good old-fashioned Row_Number(Order By X) row index.
I was wandering is it possible to use a query within another query below is the code I am trying to use.
Public Function GetInventByComp(ByVal CompID As String) Using DC As New DataClassDataContext
'need to get company id's based off names? thats bad should be name from Id need to rethink this
Dim invent = (From C In DC.Inventors_Companies _
Where C.CompID = CompID _
Select C.InventorID).ToString
[Code]...
I was trying to us multiple values in a string like "1, 3, 5" but I can't seem to get that working either so I am trying to use just a single value now. Can anyone help me? "Yes I am new to this"
I have 2 public variables that I declared in form1 of an application. I am trying to call that variable in form2 and then pass that variable in a sql query.
If I declare
Public Class Form1
Public payPeriodStartDate, payPeriodEndDate As Date
[code].....
I have two forms and I'm trying to pass a declared variable from form1 to form2 and then pass that variable in a sql query that I have in a dataset that is bound to my form. I know that my query works but it's not producing any data. I have debugged my form and can see the data being passed in the variables elsewhere on the page but I'm not sure of the syntax within the query.
[Code]...
I create a hyperlink that when clicks generates a url like so:
[URL]
And I read it into a text box like so:
Me.txtTags.Text = CType(Request.QueryString("Tag"), String)
But the result of this is that the textbox txtTags will only contain C and doesnt have the ++. I tried [URL]and the # is missing as well. But if I look at the address bar these values are there....
I have a public variable that I declared in form1 of an application. I am trying to call that variable in form2 and then pass that variable in a sql query. If I declare:
Public Class Form1
Public payPeriodStartDate, payPeriodEndDate As Date
How then to I declare that variable in form2 and how to I pass it to my sql query.
Here is the code I have for form1: [Code]
and when I debug this form, no data will appear. I'm sure that it's something wrong with how I'm either calling the variable in form2 or in the query. Can anyone offer any assistance on this?
I'm trying to write my very first "serious" program using a mysql database. I use the mysql connecter dll to connect with my database. I have a subject and a visit table. I can select a subject and I can get all the visits for all subjects in a list box with:
[Code]...
I have a LINQ query:
VB
Dim Db = New MyDataContext
Dim Qry = From cust in Db.Customers
Select cust.ID, cust.Name
And I want to pass it to a function to filter it, like this:
VB
FilterAnyQuery(Qry, cust.ID) ' WHERE "cust.ID" CAN BE ANY FIELD
The Sub should be of this kind:
VB
Sub FilterAnyQuery(ByVal AnyQry As iQueryable, AnyField as ???)
AnyQry = AnyQry.Where(AnyField = "somevalue")
End Sub
How can I pass "AnyField" to the Sub and make the LINQ "Where" clause work?
Public Shared Function getrealrequests(ByVal itemname1 As String) As ArrayList
Dim sqlStr As String = "data source=localhost;initial catalog=Customers;integrated security = true"
Dim dbRecords As ArrayList = New ArrayList
Dim dbConn As SqlConnection = New SqlConnection(sqlStr)
[Code] .....
I'm trying to pass the value of 'itemname1' to the select query. What's the correct syntax to get it to work?
I am using following code to connect to my database.
Dim conStr As String = "Data Source=.SQLEXPRESS; ![enter image description here][1]
AttachDbFilename=|DataDirectory|dbTest.mdf;
Integrated Security=True;
User Instance=True"
Dim sqlQry As String = "SELECT * FROM [tblTest] WHERE ([Name] = @Name)"
Dim dAdt As New SqlDataAdapter(sqlQry, conStr)
Dim dSet As New DataSet()
Then filling adapter with
dAdt.Fill(dSet, "tblTest")
And then I can use the data the way I want.
My question is: How to pass the value of parameter that user will give through a text box on my webform.
Dim sqlQry As String = "SELECT * FROM [tblTest] <b>WHERE ([Name] = @Name)
I mean how to pass the parameter value to my query?
Do you just need to format the date? Such as msgbox(New Date(2010, 1, 1).ToString("yyyy-MM"))
Or do you need a hashtable:
[Code]...
I want to pass a date as parameter in vb to query the data from the table.If I hardcore the value in the query it works fine for me, but if I pass it as parameter to query, like I am getting the data from edit text and trying to send that as a parameter, this does not work.
SELECT *
FROM VehicleAnalogParamDownload2
WHERE Vapd2_Date between 'From_date.Text' And 'To_Date.Text'
I am using following code and trying to get data by given parameters. I donot know how to pass the parameter value to my query.
[Code]...
I am trying to run a query an Access db from VB. The general query which I want to run is
SELECT * FROM Patient WHERE Patient.PatientID = ?
or SELECT * FROM Patient WHERE Patient.PatientLname = ?
I tried using an input box which captured the user input and pass that variable to the query, but that failed.Then I read about writing a function and using that, however, I keep getting an error which says Function not defined, but when stepping through the code, it seems to work. Here is my function:
Module Module1
Public Function LookUpNow(ByVal userInput As String) As String
LookUpNow = userInput
Return userInput
[code]....
I've been reading a fair bit about the performance of using LINQ rather than using a for each loop and from what I understand using a LINQ query would be a little bit slower but generally worth it for convenience and expressiveness. However I am a bit confused about how much slower it is if you were to use the results of the query in a for loop.
Let's say that I have a set called 'Locations' and a set of objects called 'Items'. Each 'item' can only belong to one 'location'. I want to link items that are under the same location to each other. If I were to do this using a normal 'For Each' loop it would be something like this:
For Each it as Item in Items
If it.Location.equals(Me.Location)
Me.LinkedItems.Add(it)
End If
Next
However if i was to use LINQ it would instead be this:
For Each it as Item in Items.Where(Function(i) i.Location.equals(Me.Location))
Me.LinkedItems.Add(it)
Next
is the second (LINQ) option going to loop once through the entire 'Items' set to complete the query, then loop through the results to add them to the list, resulting in essentially two loops, or will it do the one loop like the first (For Each) option?
Is it possible to do the following? [code] Basically I have one Load_Gridview function that is called on all postbacks, and rather than creating a bunch of different cases.I want the filters to stack.My actual code has more filters set up (4 or 5 of the).It all compiles ok but when I run and try to execute with active checked, or a department selected I get the following error. [code]
View 4 RepliesI have below XML file
<?
xml version="1.0" encoding="utf-8" ?><
PageFlow>
<
attributegroup name="Search"><
attributes>
[Code]...
I am looking to sum the "Status" field.
Dim _detailRecords As New DataTable
_detailRecords.Columns.Add("y")
_detailRecords.Columns.Add("z")
[Code]....
I'm also wanting to keep this as an IEnumerable of DataRow because I will be creating a datatable from it with
Dim yyyyy As DataTable = query8.CopyToDataTable
I am Fairly new to Linq and I am trying to write a simple query to return the error messages within my xml file.
<?xml version="1.0" encoding="utf-8"?>
<Error xmlns="urn:xxxxx">
The following errors were detected:
[code].....
I want to pass a comma delemited list of values as a parameter to a query I'm building using the designer in Visual Studio 2008 based on some strongly typed DAL tutorials I was going through. The query is going against a DB2 database. Here's what I want to do:
select * from prices where customer in(?)
It works fine win I pass in 123456 as ?But fails when I pass in '123456' (it is a char field so I don't know why this doesn't work; it must be adding these behind the scenes) or 123456, 123457 or '123456', '123457' I'm adding this page to a portal where all the data access is being done based on the DAL designer model with a BLL that calls it so I wanted to do it this way for consistency.
if I run this under c#
from p in Addresses where p.Address2 == null select p.AddressID
it generate this query
SELECT [t0].[AddressID]
FROM [dbo].[Address] AS [t0]
WHERE [t0].[Address2] IS NULL
if I run this under vb.net
from p in Addresses where p.Address2 = nothing select p.AddressID
it generate this query
SELECT [t0].[AddressID]
FROM [dbo].[Address] AS [t0]
WHERE [t0].[Address2] = ''
p.Address2 is a varchar field that accept null value
why vb.net is "wrong" ?