How To Make LINQ "record Class"
May 16, 2011
I am using Visual Basic 2010 Express. I am just learning LINQ, and so far loving it. I would like to use LINQ to query an ACCDB backend (built with Access 2007/2010). I am assuming that this is accomplished with LINQ to DataSet. I must use filtering criteria which are defined by the user at runtime, both in the selection of which fields are to be filtered, and in the values which are to be matched. How I intend to accomplish this (unless somebody has a better idea), is to build a "Criteria" class with members representing field, operator, value triplets (eg: fieldname="OrderCount" comparison=">" value="3"). I was then going to overload the equivalence operator so that comparisons between a "record" object and a "criteria" object would be conducted by a method of my choosing, and return true only if those field, operator, value triplets specified evaluated to true when provided a record object.My question is, what class of object is it that I must specify in my overload for a query such as:
HTML
From record In table
Where record = criteria
[code].....
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Mar 2, 2009
I have been utilizing Scott Gu's tutorials on LINQ to SQL to try to learn some LINQ. I have been able to view, retrieve, and update records but I am unable to write new records into the database (MSSQL). Scott starts getting into inserting rows in the fourth section of the set of tutorials. As you can see on that page (or may already know), in order to add a record you must do the following (VB.NET)[code]...
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Aug 1, 2011
I am trying to insert a new record though linq. I am able to update and read data with out any problem, but how to just inset a new record. Here is a start of my function.
Public Function AddAddressInfo(ByVal objdeptGUID As String, ByVal objGEOCode As String, ByVal objArressCommonName As String, ByVal objStreetAddress As String, ByVal objAddressNotes As String, ByVal objIsPublic As Boolean, ByVal objSesionToken As String)
''#Check of Token is good
If CheckToken(objSesionToken, objdeptGUID) = False Then
Return "Error"
End If
[Code] .....
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Aug 3, 2010
How can search record in my DataSet (fields: Name, Address, Phone#) for a certain name, given by user by clicking a combo box?
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Aug 22, 2011
I´m trying to update my Students table record using LINQ to SQL. The problem is when one of the Properties of the object changed and 'PropertyChanging' Event is fired using 'SendPropertyChanging()' method.
student_id is a PK
data types are matched
Here is the full ArgumentException:
GenericArguments[2], 'System.String', on
'System.Data.Linq.Mapping.PropertyAccessor+Accessor`3[T,V,V2]'
violates the constraint of type 'V2'.
[code]....
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Apr 22, 2010
What I have is a database in a Windows Form (via tableAdapters etc., basically the default stuff VS adds). What I need to do, is add a very simple record of a name and score (the "place" is an auto-number). I have not even been able to tackle sorting the table, because I can not even figure out how to insert...
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Apr 19, 2012
Our remit is to make a Veterinary Surgery Booking System.
I have an asp.net page that has 4 fields, one of the fields is populated on page load as per the vb code below.
I'm trying to get the selected value (or text) of the dropdownlist control and use it as the value for the first field in the record however every time I select the second or third value in the dropdownlist and click the submit button the new record that is created is inserting the first value in the dropdownlist.[CODE...]
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Jan 12, 2011
I am pretty confused about lambdas. What I am trying to do here is write a function that will return an object from a certain table with a certain criteria. So lets say I can write:
function GetRecord(TableName as string,Criteria as string) as object
'do the linq-stuff
end function
Now I don't care if the parameters are strings or lambdas or whatever, but the end result must be that at runtime I don't know which table and which criteria will be used. As sometimes I need to get a customer record by email and sometimes a product by id etc. If possible I would prefer returning a list of matching objects and then I would just use .firstordefault when I want 1 (such as by id...).
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Nov 14, 2009
I am using the following line of LINQ to drill down into an element. Is it possible to expands this code to drill further down so that I can add content to the <population> element in "Test2". I want to be able to do somthing like element.SetValue(1000000). However I need to expand the code below so that I can pass the entire query results into the variable called "element"'
Dim eles = From c In doc.Descendants("File") _
Where c.Attribute("Name").Value = "Test2" _
Select c
[code]....
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Nov 9, 2011
I'm very new to linq and I'm trying to come up with a linq query against a dataset that will return a max count value based on grouping records.[code]...
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Mar 24, 2011
For a school programming project we are supposed to create a database with 2 tables country, and continent.then we populate country with every country name, population and continentID. For continent we populate with each continent name.
i have completed this step, and i am able to run a linq query to display all countries and corresponding continent into a datagridview. My problem arises because we are supposed to display each record one at a time, and be able to cycle through one at a time. I cannot for the life of me figure out how to do this.
for example if i made a query to select all countries in africa, i want to beable to display the name of the country, and population in textboxes. then have a next button that will go to the next record.
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Mar 10, 2011
ok I have a weird issue. I created a master record in the master table and then a record in the detail table. when creating the detail record i get a Specified cast is not valid error. Now another weird thing is that once I create the master record I can't query and verify it was created. But when i got to sql management studio I can see the master record. Below is my two procedures and the table definitions. Master table primary key is INVNUM child table primary key it INVLIN_ID and the reference key is INVNUM
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Oct 1, 2010
The LINQ VB code below is to read the first record data for database table
ProductTable that has 3 colounms (or 3 fields):
TableCol1, TableCol2, TableCol3. The reading data is stored at variable
MyArrayFirstRow.
'-------start LINQ VB code in Visual Studio Web Developer 2008-------'
Dim MyArrayFirstRow
[Code].....
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Aug 13, 2009
I have a LINQ to SQL DataContext with all my tables and all my stored procedures in it. Let me first start off by saying that we are upgrading our project from an access project to a WPF project. So in the Access project you could set a forms datasource to a stored procedure and edit and add new information. So in my WPF project on the page load I call my stored procedure to return an ISingleResult and then call a function to set the binding on every single textbox on the form. One is there an easier way to do this and two what if I want to add a new record since the textbox's are binded to an ISingleResult?
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May 15, 2009
I can't make difference between public class and private class and friend and protected friend class.
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Jun 2, 2010
Somewhat new to SQL and processing loops. I have a non-keyed file and I want to get the next record in sequence .. grab data needed and update it as used. This class is called from a GUI interface so I only need to grab the NEXT record each time..
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Jun 13, 2010
Is there a direct way of generating a class from a record in the database?I use a program to edit records and would like to use a class that has the record fields as member for saving the last values entered while adding new records and the initial values of the fields for editing so that if i press ESC the control while editing the value returns to the original.I tried to use dim r as datarow but i get the error that there is no object
and if i declare dim r as new datarow i get the error that new is not implemented.Do I have to write the class definition explicitly?
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Sep 25, 2009
I'm trying to convert something from C# to VB.NET and I'm having trouble finding an equivlent in VB.NET to C#'s yield keyword. I realize 'yield' is not a convertable keyword to VB.NET, so can someone please show me how I would implement this code in VB.NET. I got all of it converted over except for the implemented GetEnumerator() function. It is simply a class that implements CollectionBase and IEnumerable (to make it LINQ worthy):
[Serializable()]
public partial class Customers : CollectionBase, System.Collections.Generic.IEnumerable<BusinessLayer.Customer>
{
[code]....
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Oct 14, 2009
I have a very interesting LINQ question. I have a document, that I am trying to filter results on, but to filter, I am matching on a REGEX result from one element of the XML. I have the following, working LINQ to XML to get the individual data that I'm looking for.
[Code]...
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Apr 28, 2011
Just a quick question about LINQ, I want to use a value from the returned dataset to lookup a value and return this. The line I am struggling with is .ViewingNotes = NewViewing(pt.ProspectId).GetViewings().Columns(7).ToString(). Is this possible?
With BusinessLayerObjectManager.Context
Return (From p As [Property] In .PropertySet
Join pt As Prospect In .Prospects On pt.Property.propertyID Equals p.propertyID
[code].....
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Dec 10, 2010
I have the following XML file
<Test>
<Modules>
<Module Name= "Test1">
<QueueName Name="Test1Active1" Active="True"></QueueName>
<QueueName Name="Test1Active2" Active="True"></QueueName>
[Code]...
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Sep 26, 2011
I have a collection of objects (classes I created), and each one ties to a record in a database. I want an easy way to update the information, so I thought about declaring a record in the class, that would tie to the record on the database. However, I'm having a problem updating it now.
1) Can I declare a global variable for the data context, and leave it open the entire time the program is running? This would solve my problem, but I don't know if I can do that.
2) If not, besides coming up with a complicated class to do this, is there an easier way? Here is an example of what I am trying to do:
VB.NET
Public C as Record
Public Sub GetValue()
Dim SQL As New DBDataContext
Dim X = From T in SQL.Records Select T
[Code] .....
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Feb 28, 2012
I am New to <acronym title="Visual Basic">Vb</acronym>.Net. this is my first test. i try to create small address book. but i don't know what wrong. it compile perfect but when it run it give error and not work. is there any other way to add same class like in class inside array?
[Code]...
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Apr 5, 2011
I'm trying to create a list of all my objects from several lists of objects using Union.
Return Chart.AnnotativeNodes.Union( _
Chart.DecisionNodes.Union( _
Chart.EndNodes.Union( _
Chart.StartNodes.Union(Chart.WorkCenterNodes))))
The above line gets an error because I can't union List(of AnnotativeNode) with List(of DecisionNode). Each list defined like List(of EndNode) or List(of StartNode), but each class inherits from the base type Node.Is there a possible way to union these to get a result of IEnumerable(of Node)?
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Aug 8, 2010
I call upon the VB ninjas out there. Here's my situation. I need to eventually be able to pass multiple models to a view. Currently I have a linq to sql class that, of course, has a bunch of generated model definitions. I need to make a model that implements multiple models. I somewhat understand how to do this in C#, but this project is testing my VB skillz. Here's some snippets from my linq to sql models. I need to combine these two into one model to pass to the view.
[Code]...
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May 13, 2011
I have an array of unknown (to the current method) class objects. I do know that each class has a property called "Number". I am trying to write a LINQ query where I am looking for the object with the next Number in sequence. AKA, I'm at Number 8, use a LINQ query to find the object where Number=9.
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Sep 29, 2011
I have a datatable being returned by my DAL. In my BAL I want to return a class object. So I have a class called BusinessArea that has ID, Description and Active properties. I tried this:
[Code]...
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Apr 30, 2010
I'm using the following code to sort a List(of Class) using LINQ. It works fine, but I'm wondering if there is a better way to do it. I'm basically taking one list, applying LINQ to it, then using the result to create a second list in the sorted order. Can I do this without creating a second list? Here is my sample
' KeyMatch is my Class Variable
' mMatchList is the Unsorted List
'
[code].....
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Apr 18, 2009
I hav a web service which pull records from a database and I am hosting these services in IIS which works fine but I am trying to retrieve the record and display the record in a listbox displaying the time field as the text for that record.I have created the following function
public sub get_data()
dim dt as new data.dataTable
dim service as ws webservice.webservice
[code]...
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Jan 13, 2010
Public Class form1
Private Sub btnAnswer_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnAnswer.Click[code]........
how can i make vb realize that the side that is opposite of the given angle, has to be less than the other sides. Also im not sure what Acamar meant by If txtAngleA.Text <> "" AndAlso txtAngleB.Text <> "" AndAlso txtSideA.Text <> "" Then 'two angles and a side Because im not sure what <> does.
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