[2008] Dynamic LINQ Queries And Select Statements?
Jun 5, 2008
I've recently ported my website from 2005 to 2008, and I'm using LINQ Queries to implement a search. The issue is that none of the fields are mandatory, so I've had to implement a dynamic LINQ Query (sic?). Here's the relevant code -
Public Function searchQuery(ByVal titleType As String, ByVal titleName As String, _
ByVal configMgr As String, ByVal lifecycle As String, _
ByVal CIType As String, ByVal recordsPerPage As String) As IEnumerable(Of
[code].....
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Feb 17, 2011
I use the following code to fill the Table1 dictionary with the information found within the LINQ query.
Dim DB As New DatabaseDataContext
Dim Table1 As New Dictionary(Of String, Integer)
Dim Table2 As New Dictionary(Of String, Integer)
[code].....
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Jun 25, 2009
There is not a VB.net database forum, and there is a HUGE difference (unfortunately) between ADO and ADO.net. I have a connection to a MS SQL database, which I understand is capable of handling multiple SQL statements in one Execution, ie
Using cmdExe As New System.Data.SqlClient.SqlCommand
sSQL = "Delete * from mytable where UniqueID=123;Insert into mytable (UniqueID, Field) values (123, 'something')"
.CommandText = strSingleSQLLine
[Code]....
There are two questions here actually...can I add the parameters before setting the command text, and do I have to add the same parameter over and over again?
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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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Nov 23, 2009
I have a listbox that is dynamically filled by certain values depending on what table has been selected from another list box. Once a value is selected, it is being graphed vs a date & time range. With my ignorance of linq: depending on what value is selected, the linq to sql statement I need to create to grab data from my database is different as I can't use an index on an anonymous type.
result = From t In db.APS _
Where t.DateTime >= startDate And _
t.DateTime <= finishDate And t.Weight = weight _
Select t.DateTime, t.TotalConcentration
t.TotalConcentration should be selected if my listbox value is "Total Concentration", but if it's something else, like "Temperature" or "Flow Rate" (connected to appropreate database columns) - this method obviously isn't going to work. I need to be able to dynamically select a specific column from the anonymous type list, or use some other method I'm unaware of to do this.
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Feb 17, 2011
I'm developing an application to allow engineers to conduct simple single table/view queries against our databases by selecting Database, Table, Fields.
I get how to use the Dynamic LINQ Library Sample to provide for dynamically selecting the Select, Where and Order by Clauses at runtime but I'm at an impass on how to allot for table choice.
Is there a way to provide for dynamically selecting the "from" table at run time
EDIT
So Both of the answers seem to be saying the same general Idea. I'm going to try to convert the C# into VB and get it to work.
The first answer converts to
NotInheritable Class DataContextExtensions
Private Sub New()
End Sub
[Code].....
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May 24, 2010
I need to represent the following query using LINQ:
DECLARE @PurchasedInventoryItemID Int = 2
DECLARE @PurchasedInventorySectionID Int = 0
DECLARE @PurchasedInventoryItem_PurchasingCategoryID Int = 3
DECLARE @PurchasedInventorySection_PurchasingCategoryID Int = 0
[code]....
Now, I know that a query in .NET doesnt look like this, this is my test in the SQL Design Studio. Naturally VB.NET variables will be used in place of the SQL local variables.My problem is this: All of the conditions after "WHERE" are optional. In that a query might be made that uses one, some, all, or none of the conditions. V.PropertyID and V.Value can also appear any number of times.In VB.NET I can make this query easy enough by simply concatenating strings, and using a loop to append the "V.PropertyID/V.Value" conditions.I can also make a Stored Procedure in MS SQL, which is easy enough.However, I want to accomplish this using LINQ.
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Jul 6, 2010
I will start a new project, use the queries and dealing with databases using LINQ or SQl ,Which is better to start ???
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May 26, 2010
how to associate a select case statement with, which point to four Function procedures, to four radio buttons that are used to +, -, *, and / two simple fractions in a fractions calculator. This is a class assignment for which I have already been graded. I used an If...ElseIf statment and it worked perfectly. Now I am trying to utilize the Case Statments with Function Procedures to do the same thing. I do not get graded for this, but I was told to research it an find an answer. My current code is listed below.
[Code]...
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Oct 17, 2011
This is an extension of my last question which was answered, so I am starting a new thread. I have a query in LINQ that I was given to trim down the columns of a datatable. This works well, however, I need to make the LINQ query dynamic. So the query below:
Dim qColumnsIWant = From row As DataRow In inDT.AsEnumerable() _
Select _
EPN = row.Field(Of Integer)("EPNID"), _
EPNID = row.Field(Of String)("EPNNumber"), _
Ingot = row.Field(Of String)("Ingot"), _
ShopOrder = row.Field(Of String)("ShopOrder")
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Jul 3, 2011
I use the following code to fill the Table1 dictionary with the information found within the LINQ query.[code]....
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Feb 5, 2010
I would like to bind a DataGridView to a different LINQ query every time (in order to reuse the same form/DGV for different queries), like this:
[Code]....
but the "Qry", and the number of comboboxes, and their field names would change every time.
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Feb 8, 2012
I have a class with properties in it . The properties in it are all named the same with the columns names in the database.The reason for that is that i want to loop through all the properties within the class and dynamically create an sql query with the parameters in it . Then dynamically create the parameters and add them into the oraclecommand , everything works well until one of the properties ( QTY ) is set to 0 . When it is set to 0 , during the properties loop ,it will check it as nothing and bypasses the QTY property , with that i am missing one of the columns.class with properties , Notice the property Qty it is Nullable(Of Integer) , it is because when inserting data into the database , sometimes i would want it to be null instead of default 0 .
Public Class HDB
Public Property BONum() As String
Public Property Owner() As String
Public Property Qty() As Nullable(Of Integer)
[code]....
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Aug 24, 2011
I have a basic grid of Linq2Sql entities (frmList). I have a separate form for editing (frmEdit). frmEdit has its own DataContext (as that appears to be the recommended way). How can I tell when my detail form has saved changes?
I don't see a built-in method. I am considering raising an event on the detail form when I save the datacontex, but not sure how I consume this event on frmList, and I have a feeling these events are already created for me somewhere?
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Oct 11, 2010
Let's say I have 3 tables: carts, baskets and eggs where a basket can contain many eggs and where carts contain many baskets. Each basket has a foreign key that maps to a cart and each egg has a foreign key that maps to a basket.I need to return a table that contains these 3 columns:Cart Name | Count of Baskets in Cart | Count of Eggs in Cart.Each table is an EF and I'm using linq with VB.So far, I have 2 queries: one that returns the columns Cart Name and Count of Basket and another one that returns Cart Name and Count of Eggs. How can I combine these two result tables so that I get the results in one table?
Dim query1 = (From cart In myEntities.Carts
Where cart.UserID = TheUserID
Join baskets In myEntities.Baskets On baskets.CartID Equals cart.CartID
[code]...
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Mar 13, 2012
I have a function used to filter a list of options to return only those that are lot traced, and, when applicable, also only show items matching a specified pattern:
Private Shared Function FilterResultsLot(ByVal source As IQueryable(Of Item), _
ByVal itemCode As String) As IQueryable(Of Item)
If HasFilter(itemCode, True) Then
[Code].....
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Mar 17, 2009
I have 2 tables that are related. Each app can relate to many apps. ie, office can be related to word, excel.[code]I would like to do the following query. I use vb.net but c# is ok.Query is to return all the apps that are not related to (1), so the result should be (4, quake) .
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Jan 9, 2009
I have seen different examples in Linq and one used Select and another didnt but both return the same results. Is there a reason why we should use Select ?
[Code]...
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Apr 5, 2011
I know there are similar questions on stackoverflow - and I looked through them and think my issue is somewhat similar, but haven't been able to find a solution by looking at any of these other questions/answers.I'm getting the error when attempting to execute the following code:
Private Sub btnReserve_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnReserve.Click
' Check that the room is still available.
Dim dbCheckOccupants As New pbu_housingEntities
Dim hall As String = CStr(Session("hall"))
[code]....
It is catching an error on this line:
Dim myID As String = GetID.First.id.ToString
As far as I can tell I'm not using multiple contexts?
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Apr 7, 2009
I decided to iterate through the Data.DataTable and trimmed the values there.Utilizing SirDemon's post, I have updated the code a little bit:
[code]...
I know that on the DisplayMember line the .First.Item() part is wrong, I just wanted to show what row I am trying to designate as the DisplayMember.
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Sep 10, 2009
Example-I have a person class
Public Class Person
Private _fname As String
Public Property Fname() As String
[Code]...
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Mar 31, 2011
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."
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Jun 28, 2011
Not sure if this is possible but can you use the select statements in VB to pull in from not just one but multiple tables and put the data in a gridview? [URL]
Code:
Imports System.Data
Imports System.Data.SqlClient
Public Class Form1
[Code].....
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Oct 22, 2009
This is really a continuation from my earlier post. I've never worked with this datatype/collection (system.collection.generic.Ienumerable) before so I'm struggling to declare the query globally so I can reference the results within other sub routines/functions. I also am struggling to convert it to other types.how I can convert the collection of xml elements/system.collection.generic.Ienumerable into an xmltextreader (I know I will have to change the query below as it select the value of the node and not the node itself) I imagine by converting the query result to system.IO.stream My first port of call was MSDN but I find the material very difficult to understand for this particular subject.
[Code]...
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Feb 20, 2009
Dim subtotal As Decimal = CDec(txtSubtotal.Text)
Dim discountPercent As Decimal
Select Case txtCustomerType.Text.ToUpper() = "R"
Case CBool(250) To CBool(500)
discountPercent = 0.25D
[code]....
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Jul 10, 2009
i have a situation in which i have to check if the string starts with something and then perform something....First i used "If" as below
If utn.text.startswith("Fuel") then
messagebox.show("Fuel Purchase is selected")
End If
[code]....
Now i have to use Select and Case statements along with startswith...?
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Sep 19, 2010
I am working on a calculator and I'm trying to use select case statements for the symbols selected (radio buttons) as opposed to If then Else statements. I am running into trouble because I'm only used to using them with list boxes.[code]...
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Oct 7, 2011
Im trying to figure how to use the IF, ELSE statements OR the Select Case statement to write this program.I'm using Visual Studio 2010. The program is suppose to allow the user to input their weight in a text box and from group box 1 the select whether theyre male or female using the radios and they select inactive or active from group box two and the calculate but will determine how many calories they should intake based on the criteria below.
[Code]...
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May 11, 2012
I have a method in a webservice that has parameter with which users can decide how they want to order their results. This is a List(Of String) with the names of the fields in the order they want to sort them. I know I can normally order on multiple columns by doing the following
Dim test = Bars.OrderBy(Function(x) x.Foo) _
.ThenBy(Function(x) x.Bar) _
.ThenBy(Function(x) x.Test)
However in this case this won't work since I can't chain the ThenBy function because I'm adding the sorting orders in a loop. To use ThenBy I need an IOrderedQueryable collection. This is how I would want it to work
Dim sortColumns = {"Foo", "Bar", "Test"}
Dim query = From b in Bars
For each column in sortColumns
Select Case column
Case "Foo"
query = query.Orderby(Function(x) x.Foo)
[Code] .....
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Oct 19, 2009
I am trying to write a code that converts characters in string using a case select statements. For instance if I type the word "aeiou" the the word "<>[]/", also if I type "AEIOU" then <>[]/" should print but its not working here is a sample of my code so far.
[Code]...
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