Dataset Referencing .NET Object?
Mar 15, 2010
Ive have a listview on my form and need to populate it with data from my Table called "tblCustomers". However I need to only retrieve records based on field that is populated with data called "Joe". In order for the SQL syntax to retrieve the name "Joe" then the SQL syntax needs to reference the Label on the form called "lblName" which will have the name "Joe" as the caption.
How can my dataset have SQL data that references my label object on my form?
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Oct 15, 2010
I keep getting the error "Object reference not set to an instance of an Object" on the below highlighted line of code and I understand why. It's because I'm checking for something that hasn't even been initialized yet. My question is, what's the best way to check a DataTables row count without getting that error before refilling it?
If Not ds.Tables("tblNotes").Rows(0).IsNull(0) Then
ds.Tables("tblNotes").Rows.Clear()
End If
adp.Fill(ds, "tblNotes")
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Oct 5, 2009
I have a VB6 app that I'm updating to .Net. This app interfaces with PeachTree Accounting through there type library, which I have a reference. When I try to create a reference to Peachtree in .Net,
1. Select References from Myproject
2. Click "Add"
3. Select the "COM" tab
4. Select the "Peachtree Accounting 17.0 Type Library"
When I add the reference, the Path says "<The system cannot find the reference specified>".
There is something different about the way the path is listed. All the other paths are listed like "C:Program Files..." but the Peachtree library is listed like "C:PROGRA~1SagePEACHT~1PAWLegacy.dll"
This is how the old DOS use to list names longer than 8 characters. In my VB6 app the reference path is "C:Program FilesSagePeachtreePAWLegacy.dll"I tested other references with simular paths like "c:progra~1..." and they work fine. It's probably something else. I'm fairly new to .Net so can anyone point me in the right direction?
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Jun 8, 2012
Referencing an object (class) within a thread fails
I have an object ("a vb class") that needs to run on a separate thread and communicate with the U/I.
Even using sample code, I cannot get the object to run within a thread. I demonstrate this problem with two examples. The first calls a function within the form and it works perfectly. The second creates an object and performs the same calls, but fails.
example #1 [working] (Called within a form)
Private Delegate Sub FuctionToBeRunInThreadDelegate
Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
[Code]....
SUMMARY: When the thread creates the object, it appears that the object is not actually running inside of a thread or else form.InvokeRequired would be true. I have other more complex examples where this is strongly verified and evidenced, but I provided these two as a very simple demonstration of my problem.How can I have a thread "own" a series of individual objects so that the objects are run asynchronously and can independently report back to the U/I?
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Dec 30, 2009
i'm trying to reference an object dynamically inside a loop; something like this:[code]
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Sep 19, 2010
Often I have a list of object A, and I have another object type B that needs to hold a reference to one instance in that list. So, as far as I can imagine, it's three ways to hold such reference:
1. Make B hold the instance variable of type A
2. Make B hold some other key/ID of the A instance
3. Make B hold an integer of the list index of the A instance
I guess 3 is quite limited, and mostly suited for use locally inside a method, in a for-next loop etc. But with the other two I tend to have the feeling that I should use 2) over 1), as I believe I shouldn't "duplicate" the object.. But wonder if that is a mistake. I guess it's only holding a reference to the stack memory, so it doesn't really make any overload compared to holding just an integer key/ID..
Further my thought is that with 1), I don't have to loop through the list to get the correct instance, as it already holds it. However if A changes, it may not be reflected in B.A, if the A has been given a new instance, so then 2) would instead give access to the updated object A. So perhaps if A is a "dynamic" object that may have been reinitialized (if that's a word), I need to use method 2). However if it's a type of object that is only changed when for example the user opens a program settings form, and this setting form only changes value type variables, then perhaps 1) is appropriate?
This is kind of the case I have some times, and I wonder if I should then use 1), as it doesn't require me to loop through the list by key/ID. It makes other object hold the full reference, which is not really necessary, but maybe still more efficient? Although at the same time, maybe I shouldn't really care much about looping through an object list either, if the list is not very big.
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Oct 8, 2010
I have several sets of similar objects (labels, progress bars) on a form in Visual Basic 2010 on Windows. In my code, I have collections that contain data, which needs to be pushed into the value/text property of each.
I would like to get a solution similar to PHP in that I can assign values somewhat like:
For ID as Integer from 0 to count(collectionExample)
lblExample{ID}.Text=collectionExample(variableID)
...and as such to loop through so each of the different lblExample's were updated to their corresponding value.
The issue I have come to is that I cannot seem to reference an object on the form using a variable. I have also tried using something like
CallByName("lblExample" + variableID, "Text", CallType.Set, exampleCollection(variableID))... however I still can't combine the string and variable to reference the object.
Any solutions on referring to objects in VB2010 by combining a string prefix and a variable string identifier, similar to PHP's $variable{$variable} approach?
Edit: Windows Platform
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May 10, 2011
I have an application that creates desktop shortcuts. To do this I have to reference the Windows Script Host Object Model. When I add it as a reference, it always creates the DLL, Interop.IWshRuntimeLibrary.dll, in the objx86Debug directory, then references itself to it, rather than looking at wshom.ocx. Even if I add reference wshom.ocx it reverts to saving the file in the objx86Debug directory. The problem is if I move my application to another computer without that DLL being present, the program fails to run.
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Sep 9, 2011
I have an asp image within my "default.aspx" page.I set cookies on my masterpage vb file and depending on the cookie set, I want to show or hide this image.
default.aspx
<asp:image ImageUrl="/images/myimage.jpg" runat="server" ID="myimage" Visible="false"></asp:image>
mymaster.aspx.vb
[code]....
I get the following error:
'myimage' is not declared. It may be inaccessible due to its protection level.
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Apr 3, 2012
I was given a task of rewriting some Crystal Reports. I found the original reports circa 1999, opened them up in VS 2008 made the changes and saved them.Now, they reference a database that is no longer around. So, I deleted this data source and added a .NET OBJECT datasource. I changed everything around so that the fields now look at this new datasource.
My intent was to create the report and during run time, pass it a datatable. This table is created by running a sproc created.When I run it, I get the first page of the report. But when I try to change pages or print, I get an error: Logon failed. Details: crdb_adoplus : Object reference not set to an instance of an object. Error in File C:...MR01 {8E5164A9-4B01-4019-81E6-87AED65A02DF}.rpt: Unable to connect: incorrect log on parameters
[Code]...
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May 26, 2011
I have a collection (IList(Of Sample)) of the following class:
Public Class Sample
Public sampleNum As String
Public volume As Integer[code].....
This collection is filled from a regex that gets passed over a file.What I want to do is use Linq to generate a collection of these for each unique samplenum using the following conditions.For each samplenum: Have the highest volume where the final is greater then one
If the sample has multiple records for this volume then pick the one with the the highest final
If the previous step leaves us with no records pick the record with the highest final ignoring volume
I am extremely new to Linq and just can't get my head around this. For now I have solved this using for each's and temporary lists but I am interested in how this would be handled using pure Linq.Sample Data:
samplenum | volume | initial | final
1 | 50 | 8.47 | 6.87
1 | 300 | 8.93 | 3.15[code]......
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Jan 31, 2010
I'm new to programming and am trying to learn how to developed data driven application and was wondering which method is recommended? I know there are some debates out there but most of the books I have recommend using object binding, but it doesn't offer any concrete information on how to implement it. I went to MSDN and most, if not all, the documentations are on dataset. So I guess my questions is, object vs dataset, which do you use?
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Feb 25, 2012
The problem is as follows, a group of users (~50k) must be filtered from a DB, four fields for each user must be saved into a variable, then a second process will take each user and proceed to enable some licences into another system/platform. Both processes will be developed into the same application.
My first attempt was basically a query looping through the users but I wonder if thinking in objects is a better approach.
I was thinking in a structure inside an object to hold the 4 parameters, then pass each user object to the other object however considering the amount of data I'm not sure if this is fine.
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Nov 7, 2009
I am writing a program with VB.NET, there I have to select data from one table. Then I have to update about 4 tables and insert to 2 Tables. Which approach will be ok for me? I'm thinking to use DataSet.
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Aug 30, 2011
This is my first post here so forgive me if I am not following any correct protocols. I am attempting to generate a DataSet and bind it to a datarepeater object. I had been doing this at Design Time and was getting an error message when filling the dataset when the form loaded. So I am basically createing the dataset in my code now when the form loads and binding it to the datarepeater. However, when I attempt to bind the dataset I get a NullReferenceException - even through I know that there are 60 rows of data in the dataset table.
[Code]...
As you can see i have several debug messages in there. I get the error on the last line when setting the datarepeater data source. I try and get data for a specified lot - if it doesn't return any values I create some values in the datatable and add them to the DB. On first load when there is no data this works perfectly. If I then close the form and reload it, it will display fine. However, if I change any of the data (database is updated) and then go back in again, I get the error above.
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May 18, 2009
I am trying to read JSON data from a server to a dataset object, any idea on how this can be done. I have tried using the DataContractJsonSerializer class but it only seems to work for objects.
JSON Data
{
"firstName": "John",
"lastName": "Smith",
[code]....
The code above works to an object, but I want to parse the JSON data to a dataset object.
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Jan 13, 2012
I run VS 2010 Premiuim version. I do a lot of data projects and wondered what option i have to setup concurrency if the returned object is a dataset and how do i do it? Does VS 2010 have any built in options for me to take advantage of?Or if anyone else has any other ways of doing this please advise or point me to any articles.
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Nov 14, 2009
In a vb .net winforms app I am trying out something for "wide and shallow" children of a record. I use strongly typed business objects ( Strataframe ).My plan is to have a number of "child tables" collected in a dataset I drop on the form. they have no correspondence in persisted data, so the dataset is untyped and I am creating the schema through the property sheet for the tables. Each table is the datasource for a datagridview in the interface.
In my proof of concept sample, My main businessobject (CustomerBO) interacts with a SQL Server 2008 table with fields - pk, name, - and a third column which is currently varchar(max) as I considered XML but could just as easily be varbinary(max) if that works better for holding the serialized dataset.
bo.bigfield will be the strongly typed prop I want to hold the byte() array or XML or whatever that represents the dataset for that record.So, the question in a nutshell - how do I convert a dataset to a single datum and reproduce the dataset from that datum. This is my first foray into datasets, datagridviews as well so if there are better ways to accomplish any of that I'm listening.
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Nov 8, 2011
We had plan to create a three tiered architecture database application, where the middle tier will be implemented using Web Service. We're going to use Linux for the server, so I think for the web service to be able to be implemented, we only had PHP/Java left. Is this right?
The constraint is, we're going to use VB.NET for the client application.We already had a two tiered VB.NET application from our last successfull database application. It use a lot of DataSet for the result of SQL execution. Now, what I had in mind, is a simple approach of converting all procedure that return a DataSet Object, to be a WebService method. But, because of this thinking, I don't think we can do it in Java/PHP. That is, we'll be enforce to use a ASP.NET approach. Is this correct? I assume my answer from this article Consuming a DataSet from an XML Web Service (ADO.NET)
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Jan 27, 2010
I am instantiating a form object in my code behind the dataset just to access some form level variables and to occasionally set a label in the navigator bar. Recently in the b2 Team version of VS2010 there are some strange errors thrown in the immediate window and then I'm tossed out of debug mode and back into the IDE. This code has been operating for some time in this project without this behavior. A team member has just reproduced the behavior in his development machine also.The error that starts the shutdown of the debug instance is this: Control accessed from a thread other than the thread it was created on.
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Aug 26, 2009
I'm calling a webservice using the async method, and catching the response with the completed event. When I first open the form, it all runs fine, however the second time I run the form I get the above error when attempting to sort the data.
Strangely, if I comment out the sorting code, it loads perfectly, and I can manually sort the dgv by clicking on the columns.
Code:Private WithEvents Tempws As ws.wsPrivate ID As Integer
Public Sub New(ByVal ID As Integer)
' This call is required by the Windows Form Designer. InitializeComponent()
[Code].....
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Mar 14, 2011
I want to add a "object" as a data source... then fill a "dataset" using the datasource?
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Jul 10, 2010
I am somewhat new to object oriented programming and am attempting to flatten a Linq object hierarchy by using a shim class.how to initalize a derived class with property values from a base class?I have two objects, a base object with about 100 properties, and a derived object which inherits from the base object and adds a few additional properties beyond those of the base object. My simple constructor creates the derived object, but I am looking for a way to initialize the derived object properties with values from the base object.Right now I am using reflection to iterate over the properties individually and I suspect there may be a better way. The following example shows my shim class constructor for the derived class, and two properties:
newProperty1 - a new string property of the derived class
flattenedProperty2 - a new string property of the derived class, copied from a 2nd-level object of the base class
Code example:
Public Class derivedObj
Inherits baseObj
Private _newProperty1 As String[code].......
Is this the correct constructor approach to flatten the object hierarchy using a shim class? My second question relates to initialization of properties in the derived class. The constructor above creates the derived object, but what is the best way to initialize the derived object properties with values from the base object? The following code uses reflection to iterate over the properties individually, but I suspect there may be a better way.
Code example:
' property names are in the string array fieldNames
'baseObjQuery is an ienumerable of baseObj
'derivedObjList is a list of derivedObj[code].....
Is there a simple way to initialize values for the properties in the derived object based upon the values of the common properties in the base object?
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Apr 24, 2012
I am a self-taught noob and have been given the task of developing someone elses code. I have rebuilt someone elses solution into my dev machine and able to run with some minimal bugs. I don't know where to add an .xls file into my solution
System.IO.FileNotFoundException was unhandled
FileName=TestRec.xls
Message=Could not find file 'TestRec.xls'.
[code].....
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Apr 25, 2010
I have a line of VB code which looks like this : If GroupTagDropDownList.SelectedValue Is "1" Then The system doesn't throw up any errors for it but the statement doesn't appear to work.
I think that the problem must lie in how I've referenced the '1' value - I've tried putting single quotation marks around it but it appears to make no difference at all.
There is definitely a value in the drop down list of value '1' but it doesn't appear to be read at all.
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Sep 9, 2010
I have been given a .dll file (implemented in C++) that I want to use in my VB.NET application.When I try to add a reference to this dll using Visual Studio I get the following error:A reference to 'path-to-dll' could not be added. Please make sure that the file is accessible, and that it is a valid assembly or COM component.
Based on this error I concluded that I need to register the dll. Since it has been implemented with unmanaged code I tried to use the regsvr32 tool to register it. But when I try to register the dll using this tool I get the following error:Name-Of-DLL was loaded, but the DllRegisterServer entry point was not found. This file cannot be registered. how do I add a reference to this dll in my VB.NET application?If I have to register it, how?
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Aug 10, 2011
Imports System.Runtime.CompilerServices
Module StringExtensions
<Extension()>
Public Sub Print(ByVal aString As String)
[code].....
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Mar 15, 2010
When the user clicks an "Edit" button on my form, I want a box to come up which allows the user to edit a DataTable in a strongly-typed DataSet. What's the best way to do this?
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Jan 28, 2010
I have code running in the Datatable.ColumnChanging event in my dataset. This dataset underlies a form and conventional drag/drop controls are in place for data entry.when the event triggers and runs, I am running code in the form that checks the dataset.HasChanges property. It is showing False. But this is immediately after the ColumnChanging event has been triggered.Okay, I see by others posts and MSDN that .HasChanges will only be true after moving off the row with the changed column. I have also noted lots of discussion about the advanced binding property of DataSourceUpdate Mode, but that does not address this issue.I guess I can do this by checking the state of the row for the binding source. Just seems odd that the event behind the dataset can be triggered and that does not change the dataset.HasChanges property.
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May 14, 2012
I have tried everything I can to get beyond this error which shows below as <<<<< error here. It is trying to fill a dataset from a data adapter. If I change the SELECT statement to just SELECT * FROM xTable I get the correct number of records in each table. But anytime I try with a more complex statement I get the error message shown below which indicates System.Data.Common.DbDataAdapter.Fill(DataSet dataSet. I've completely erased all data and entered a new set of test data so I know there is no problem with relationships. Each table has primary key which is foreign key in other table. IS there something wrong with the Imports section: Imports System
[Code]...
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