Some .ToString - Don't Get Any "null" Errors When Processing Values From A Database
Aug 9, 2010
I have some .ToString questions.
I noticed that when I try to use this I don't get any "null" errors when processing values from a database.
strMyPhone = objParentsDataReader("Emergency Phone")).ToString
Could you explain why using or not using .ToString make the difference?
Also is it always good to include .ToString and does it make the program execute slower?
Maybe there is a document that tells use the best time to use .ToString?
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Mar 18, 2011
I just learned some basics of multi threading in VB.net recently as I came across processing a large List of records and inserting them into SQL database one by one.
I have code look like this:
Private Sub btnLoadNow_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnLoadNow.Click
Dim autoLoad1 As New Thread(AddressOf AutoLoad)
autoLoad1.Start()
[CODE]...
Itemlists is a global lists i retrieved from database, everything looks fine to me but when i run this program, I found that the threads are inserting one records 9 times into the database(I have 9 threads in total), which makes me think that maybe i need to specifically assign 1/9 of a list to each thread? Is there another way to do it which doesn't require the splitting of the list, if not , how do i split it then assign?
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Oct 15, 2009
Ive created one database Sql Server Compact Edition 2005, with one table ("Cliente") I know that I can created my database good, but i have a problem saving information since three textbox, in my table(With columns "Nombre" "Apellido" "Cliente". In my form there is a button save ("Guardar"). When I do click in my button appear the next message : "The column cannot contain null values. [ Column name = Nombre,Table name = Cliente ] " and happen the same with apellido and Id_Cliente. And this happen becouse my code cant save the information....
This is the code
Option Explicit On
Option Strict On
Imports System
Imports System.IO
Imports System.Data
[CODE]...
And the code for my button is:
Private Sub cmdguardar_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdguardar.Click
Dim myconnection As SqlCeConnection
Dim mycommand As SqlCeCommand
[CODE]...
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Nov 17, 2011
I am working asp.net vb application. I have set of values to be inserted to Database.But their some fields are optional to be filled. I need to check the textbox empty. If empty I should not enter the value to Database. How to work on this?
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Jan 1, 2012
I am looping thorugh a datatable and and printing each row to the console and I keep on getting a dbnull error. I inserted an if statement in my loop to try and catch it, but I can't seem to get it to work.
[Code]...
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Jan 5, 2010
How update the Access database in VB.Net with NULL values using OLE DB command
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Jun 7, 2011
i am working in windows appl vb.net 08. And i am working in Access DataBase.I have one Table Called "Person" . In this "Person" Table one Column Name Called "OtherName". In this Column binded in one of the Combobox in a Form.But the Problem is "OtherName" Column having the Null Values.Before i bind this Column to Combobox i want to convert this NULL Values to String. Why i need the values in STRING means , In my code i using this Combobox as a filter in SQL Query.If i didn`t change the Null Value to STRING , The Combobox SelectedText or SelectedValue is Showing Nothing. So i am not able to get the Record.
Whn i write a Sql Query to Combobox and apply filter in WHERE statement like Combobox.Selectedtext or Combobox.SelectedValue In "Selected Change Committed Event" then i should get the record in the Output right but unfortunatly i am not getting the Record. The Record Count in DebugPrint showing 0.
[Code]...
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Jan 6, 2010
2008 Array Processing and Sequential File Processing
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May 19, 2011
Im a college student and this is my first programming class, i am having extremely diffcult time with arrays and sequential file processing. Im not asking for the whole program, just something to get me started and hints along as i progress with it. Please help me get started on my program, its due in 2 days.
Here are the requirements....
1. The program must input any number of individual�s last and first names using two separate textboxes.
2. The array of names must be sorted by the last name using a bubble sort. You must code the sort.
3. The program must be able to recall the names from the file and add to the existing list of names so that more names can be added to, sorted, and written back to the file in sorted order.
4. Sort in ascending order: A to Z
5. All names must be displayed in a listbox in sorted order when the user wishes to see them.
6. In the listbox the last and first names must be separated by a comma and a space. Example: Smith, Mary
7. The user must be able to search for a name in the array, using the binary search algorithm. You must code the search.
8. Do not use module-level variables. Instead you may choose to use Static.
9. The program must be designed using Visual Basic 2008
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Dec 16, 2010
1. What's the difference between ToString and ToString()? (i do know that ToString method is to cast numeric values to string but don't know how to get it to work)
2. Why do i need XML comment feature? is it necessary?
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Feb 16, 2012
I've come across an error I'm not quite sure how to get rid of, I've got a listview with listview items making up the grid, I've got values coming from a database populating the cells however if there are any null values(in this case, there's null values in the date) it crashes my program. I'm not quite sure of a way to allow the listview to have null values in it, I figured it would default allow it but that's not the case.[code]....
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Jun 3, 2011
what is the code for allowing null values to appear on the textbox
Dim i As Integer
dg1.DataSource = bs
i = dg1.CurrentRow.Index
Patient_Profile.Txtpatient_id.Text = dg1.Item(0, i).Value
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Jul 30, 2009
I have a databound DataGridView and use a button to control updates.
The problem is that if a db Column does not allow a null value an error is thrown ("Column <ID> does not allow null values") and then the datagridview automatically removes the row. This error is raised as soon as the user leaves the cell and before the update command is issued.
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Jun 9, 2012
I doing a project for my office. In that I am showing the values and strings from a particular table based on the date range and vendor selection. It is working fine with the date range. Except within the date range if the particular reader has no data it throws an error message like dbnull string.
[Code]...
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Jun 4, 2012
I have an SQL query that gets a max value so that I can decide the next value to use in an ID field. The code works fine when there's a matching result, but if the query returns Null, it throws a Specified Cast is Invalid error.This is the code I'm using:
LastID = DirectCast(SQLQuery.ExecuteScalar(), Integer)
What would be the proper way to check for a null value?
I suspect this is going to be one of those cases where within 2 minutes of posting myquestion, I finally hit upon the right combination of terms in Google to find what I'm looking for...
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Oct 15, 2009
I'm trying to import my xls files to sql server, but i saw some values become null even though data in excel values are exist.
below is my connection string :
Code:
Dim cnstr As String = "Provider=Microsoft.Jet.OLEDB.4.0;" & _
"Data Source=" & txtfName.Text & ";" & _
"Extended Properties =""Excel 8.0;HDR=YES;IMEX=1"""[code].....
This error occurs while i'm importing the alphanumeric values into text, but previous values are numeric (but string datatyped).
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Jun 25, 2011
I have a bunch of tables who share the same kind of information, but each table has a different name for each. (There was no standardization on the naming scheme). Some tables have important data that others do not contain. Some tables that have shared important data, but they are null values. I'm writing a program to combine all the tables into one master table.
The problem is when I read in a field, the reader.getvalue(i) is null, and I cannot use that value to insert into my new master table, obviously. The null values are so random, and I cannot write IF THEN statements for every single field for every single table in the database. I'd have thousands of lines of code constantly checking for nulls, and then trying to figure out what to do with them. What can I do to convert these reader values from NULL into something VB/SQL can handle? ere is the code so you can get a picture of how I'm approaching this problem:
[Code]....
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Mar 18, 2010
So I'm writing a simple piece of code to take a series of strings, go through them, and replace and add values as needed, and then dump them all out to a text box. However, when I run the code I'm getting 3 null characters at the end of each line except for the last one. What am I doing wrong?
Code:
If isPet.Checked = False Then
While intI <> lenCode
Try
lineHold = codeHold(intI).Split(",")
[Code]...
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Oct 8, 2009
Have read most of the null value posts here, and I have managed to get things working as far as a "next record" button for my database application form (there's some awesome advice on this forum!). I have just one question, though. How do you manage saving of blank text box values from a form? I am using JET, but when I try to save an updated file that has a null value, it is not letting me. I got around it by forcing the text boxes with null values to contain " ", but obviously this is not the bext solution!
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May 29, 2012
I have the followin problem. Opening a table using SqlDataAdapter, numeric columns(sqlDbType = int16, 32, 64) that allow Null value, are set in my dataRows to 0.I am using Visual Studio 2010 and Sql Server 2008.Here's my code:
Dim cmd As New SqlCommand
Dim ds As New DataSet
Dim dt As DataTable
[code].....
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Nov 10, 2011
I'm confused at the variety of different ways to say "null" in VB.net. I've got text and numerical fields with checkboxes to mark unknown values; I just want to populate a table with the fields' values (if the corresponding checkbox is not checked) or null values (if checked) so I can later input them into a mySQL database.So my question is just which of the various null types I should be using in what situations.
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Jun 3, 2005
I have a dataset which I wish to export to XML. The writeXML function works fine, but if a value in my dataset is a NULL, it doesn't export that element at all, for that row. I would have expected it to export at least an open and closed element.
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Feb 9, 2010
Some tables I am dealing with have null values and are throwing errors. So far ive tried a few solutions to deal with the nulls with no success.Here are the code samples from my efforts so far;
If (r("datemodified").Equals(DBNull.Value)) Then
datemodified = String.Empty
Else[code]....
i have ran the query and it is working ok (i.e all the cols exist)
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Dec 27, 2011
I have used XML serialization to persist objects in my application but I am now interested in using null- able Data types for properties. Will I still be able to serialize?
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May 19, 2012
the combox is bound database table,but it is not displaying the contents of table in database,instead it is displaying corresponding null values(blank).it is showing just "select" and the blank spaces corresponding to the number of items in database
here is my
Function combobfill() As DataSet
addconnection.Open()
Dim selectstring As String = "select materialsname from materialtype_table"
[Code]....
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Jan 12, 2012
Dim myreader As SqlDataReader = cmd.ExecuteReader
'read information from the database and give the values to the arguments(column_1, and column_2)
While myreader.Read
column_1 = myreader.GetString(1)
column_2 = myreader.GetString(2)
.....
I get an error when the data returned from myreader.GetString(2) is NULL. How do I check for nulls before assigning column_2 a value?
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Jan 4, 2010
I have a database that has null date values in it. When I call the columns from the database with the null datetime values and display it in the datetimepicker text box using a dataset, theres always values in the datetimepicker text box. It sets everything that was in the database with null values to the current date. This is what i have..
DateOPStartedRevisionDateTimePicker.Text = ds.Tables(0).Rows(0).Item(13).ToString
I just cant figure out a way to get the datetimepicker text box to display nothing if the values are null in the database.
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Jul 8, 2010
Some tables I am dealing with have null values and are throwing errors. So far ive tried a few solutions to deal with the nulls with no success.
Here are the code samples from my efforts so far;
If (r("datemodified").Equals(DBNull.Value)) Then
datemodified = String.Empty
[code].....
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Apr 26, 2011
What are NULL values? Sometimes when I try to assign a query to variable, I get error saying:
Type-Cast-Error. txtMiddleName.Text = Reader.GetString(2)
How can I put it that if the value of the Middle is nothing then txtMiddleName.Text = "". Working on VS 2010 (VB.net) EDIT 1: This is the error Message I get (Line 364 is the above mentioned code)
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Dec 15, 2010
I am building VB.NET application that takes data from text files that are exported from a legacy DOS program. These are written to a datatable and displayed in a datagridview. Right now my code simply loops through the datagridview and inserts the data into the database (SQL Server). There is a requirement now that the client number must be checked before the insert to see if it exists in the database. If it does, then the value of one field (tax rate) is checked against the value of the field in the datagridview. If there is a difference, then the rate is to be updated in the database and the data that was in the database is to be written to a history table for audit purposes. If the client number is not there, then we are to do the insert (which is already written). I want to know what is the most elegant and efficient solution for this problem.
I need to compare what is in the database table with what is in the datagridview, update the history table for records that exist, and then insert new records.
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