Avoid NullReferenceException - Make Two Calls With The Datareader
Dec 17, 2010
I'm fairly new to .NET programming. I am trying to check if there are settings in a database table and if not, create some default settings. The problem is that when there are no settings I need to make two calls with the datareader and it keeps giving me problems. I originally was only using one datareader but made two to attempt resolving my issue, didn't work. Then I tried closing the datareader and I get errors because it returned a nullreference.
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Feb 9, 2010
I am having a little trouble with an 'IndexOutOfRangeException'. I think it is because when the code tries to get the DateModified col from the database it sometimes contains NULLS (the users haven't always updated the page since they created it).
Here is my code;
s = ("select datemodified, maintainedby, email, hitcount from updates where id = @footid")
Dim x As New SqlCommand(s, c)
x.Parameters.Add("@footid", SqlDbType.Int)
[Code]....
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Feb 20, 2012
Trying to make a call to another forum to chance some text boxes on it and update it. I had it working I thought but the values were not holding when I closed the box so I came up with this solution but Im getting null exceptions.[code]....
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Jan 28, 2010
Once I click Sign in, I want the application to test to see if the user has internet. If it does I want it to call another sub. If the network is not available I want a message to come up and say Error, no internet connection.
This is what I tried but can get it to work If My.Computer.Network.IsAvailable Then Call testnet()
else Messagebox.show("Error", "Truoble connecting to data base")
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Jan 11, 2009
i wanna make a program with vb that can make pc to phone calls and i wanna know if it is possible with vb or if i need another program because im new to this programing thing
i added a tool in toolbox called phonecall but however i cant use it i dont know why
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May 8, 2010
What the Win32 API is? I have looked around but no where really outlines what it is. Is it basically a set of procedures, outlined by Microsoft for programmers in order to get services from the operating system? In essence is it the equivalent to making system calls abd and library calls in UNIX? And yes I now Windows makes library calls too.
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Feb 20, 2012
I have an SQL statement like:
SELECT FNAME, LNAME, CITY from EMPLOYEE
How do I create a multi-dimensional array from a datareader which should store values like:
John, Doe, LA
Mike, Johnson, PASADENA
Freddy, Kruger, Long Beach
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Jul 12, 2011
The scenario is that an ASP.NET webforms page will call a web service in an async manner to make about 8 web service calls to various providers for data. I would like to run them in parallel to speed things up. I also need to wait for them all to come back before moving on.
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Dec 16, 2009
I am trying to create an application that will make calls to an API. I want this process to be fully automated to run a few times a day. What kind of application in vb.net can be automated? I've created windows applications in the past, but never automated anything.
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Jan 26, 2012
Using the code example on the Twitterizer website I am trying to post a tweet to twitter with this code:
Dim asyncResult As IAsyncResult = TwitterStatusAsync.Update(
tokens.Tokens,
Tweet.Text,
[Code]....
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Feb 28, 2012
I want to use a database table as a a queue...but the processing of these messages cannot be done from the database.I have a table that stores the requests i get from a .Net component. I now have to read the data from these tables and make http calls to 2 webservices. Based on the response received from the webservices, the data gets archived or deleted.I had a few specific questions:
1. How do i make sure that if i pick a record for processing and the http call fails I should be able to go on to the next record, and then come back to this record at the end of the run
2. Is there an alternative to using the database as a queue(like MSMQ etc.), which option is better
3. I want to maintain an audit trail of the record status. Is creating a trigger to log the changes before the edit the best way to do it?
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Mar 4, 2010
I have been using DBTransaction for my current projects that access a single database. However, I read some documentation on TransactionScope and was wondering in which scenario would using TransactionScope be better? Or should I be replacing DbTransaction calls with calls to TransactionScope?
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Sep 20, 2011
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In my program, I created a list of a class that contains 5 picture boxes, a button, a label, an identifier, and some other stuff. I've got roughly 65 of these in this list. I'd be stupid to hard code all that in. The identifier is a 2nd way of identifying which specific location I'm working on.
Anways, all this is created at compile time. Works perfectly fine.
I then manually start a background worker that pings a collection of components. Based off the success of those pings, the picture boxes are enabled or disabled. Basically a proactive way to see if a collection of devices over multiple locations are actually working.
It's the background worker that fails because of thread-safe calls.
Private Sub bgwStatus_DoWork(ByVal sender As Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles bgwStatus.DoWork
Dim status As Integer
[Code].....
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May 12, 2012
how I can control the tool tip popup or make calls to the text that displays based on a integer value. I'm wanting it to display a text based on a interger value inside an if statment for a picture box. So if the ingteger = 1 then tooltip.text = "" else tooltip.text = "" but that is not the correct syntax.
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Aug 17, 2009
I have a problem with my project. here is the problem:
My code for login is as follows:
dim conn as SqlConnection = New SqlConnection("Data Source.................)
dim cmd as SqlCommand = New SqlCommand("Loguser",conn)
cmd.CammandType = CommandType.StoredProcedure
[CODE]...
Now the error i get is that "there is a datareader associate with this connection that need to be closed"
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May 25, 2010
I have an application that I am reworking. It has many reports and a pain to compile and roll out.I'd like to make a root user interface that "calls" the functions and subs remotely.I was concidering pulling them and making formless exe's of them, passing the needed criteria via command line. Yet still be able to update and control them.
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Jun 22, 2010
i am working on a search feature for a program i am working on and i found a tutorial online that provides some insight but the actual code, after being modified to fit my aplication, does not work. i get two different errors as of right now, one that tells me "the value of type 'System.data.sqlclient.sqldatareader' cannot be converted to '1-dimensional array of system.data.sqlclient.sqldatareader" and the other that says"argument not specified for parameter 'array' of 'Public shared function... anyway i am kinda new to this and here is what i have so far. any advice?
Private Sub SearchOKButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles SearchOKButton.Click
[Code]...
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Mar 30, 2011
I have the following code which does what it's supposed to do:
objSQLCommand = New SqlCommand("select * from table1", objSQLConnection)
objSQLCommand.Connection.Open()
objSQLDataReader = objSQLCommand.ExecuteReader()
While objSQLDataReader.Read()
[Code]....
But I need to loop through the objSQLDataReader 1 more time. How would I do that?
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Jul 6, 2011
I got the error message There is an open data reader associated with this command which needs to be closed first by using the following code:
myCommand = New SqlCommand("SELECT BookCode FROM tblBook",myConnection)
myReader = myCommand.ExceuteReader
While myReader.Read
[Code]...
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Jan 12, 2012
I want to get a list of all students who were at one of two events. Here's my function to get an attendance list:
Private Function AttendanceList(ByVal Mode As AttendanceListLookupMode, ByVal AttendaceTypeID As Integer, ByVal EventID As Integer, ByVal EventOccurenceDate As Date) As IEnumerable(Of Integer)
'Get the attendance table for specified event[code].......
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Nov 21, 2009
i want to know how to use api calls in vb.net2008. in visual basic 6.0. we can find the list of api calls in add in manager . in vb.net2008 how to find it..
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Jun 16, 2010
For some time ago I have notice that my App on every start make a call to csc.exe and starts it. I have google-it and found out that csc.exe is some kind off on-the-fly compiler for C# (If I understand it correctly ) but my App is in VB.net. VB.Net code to make my App on every start calls csc.exe?
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Jun 10, 2011
I am copying sample.csv file's content into the new.csv file. But I need to add additional column in new.csv file which holds the default value as "Yes" for each row that exists in old file. Here is the code I have written.
Dim ioFile As New System.IO.StreamReader("C:sample.csv")
Dim ioLine As String
Dim ioLines As String[code].....
The first four columns ID,Name,Number,Amount are present in sample.csv.I am adding additional column Copied which should be "Yes" for each row.
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Mar 18, 2009
If my Select statement finds data that matches the criteria, how do I get myReader (DataReader) to read each record when there are more then one record found?
Dim myReader As MySql.Data.MySqlClient.MySqlDataReader
myReader = myCommand.ExecuteReader()
If myReader.Read() Then
[code]....
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Sep 21, 2009
I am trying to tag of some words.There are 5 tag word in my database. but only the first record is coming.i want to
my codes
Public Function tags(ByVal ID As Integer) As String
[code].....
my html code in gridview <%#tags(Container.DataItem("ID"))%>
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Apr 26, 2011
Hey Friend i am using a form with a *combobox*in which the items i have taken from the
sqldatabase named as balance and that sqldatabase have two columns one is customername and the
another is obbalance now .
In the form i had binded all the customer names from the table and now i have a textbox i want to do is
when the user selects the combobox.selected item any one customer name i need to display the obbalance of the selected customer in tat textbox
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Dec 12, 2009
two DataReader in one TreeView ?
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Jan 27, 2010
I am working on a project which requires me to connect to a MySQL database. From there I query the database and need to do work on the returned values.
I can query the database just fine. However, now I need to do work on the results. The two columns returned are user_name and user_password. The rows are the user accounts. I would like to take my query results and put each column into its own arrary().
[code..]
Instead of writing the results to the console, I would like to write each column to an individual array. Is there an easier way to accomplish this task? Or, what is the code I must place within the loop to do this.
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Oct 21, 2010
I am getting a NullReferenceException was unhandled error when i run my debugging in this part of my code:Dim x As Integer = Val(index.Chars(0))
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Dec 13, 2010
This should be fairly basic, but say I have a Public property as local variable on my WCF service, and I set this in one call to the service. Is there a way to preserve that data for another call to the service? (Without writing the data to xml or a db, and re-referencing it or anything like that)
Executing the calls from the Winform:
Public Class ClientSideWinForm
Private proxy As ServiceReference.Client
Private Sub Client_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
[Code]....
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