Handle SQL Null In .NET?
Jan 19, 2009
I read stuff from a SQL DB (database) using a data set. Some of the columns in the DB may contain NULL. I want to go through the table in the dataset and print, or use in some other way, the data. But when I try to use a certain data that corresponds to a NULL in the DB my program crashes.How can I detect - in the dataset - that it has no value and that I shouldn't try to use it?
Private Sub Get�rendenLista(ByVal e As System.EventArgs)
'----------------------------------------------------------------------
' This function fetches a list of �rende from the table �rende
'----------------------------------------------------------------------
Dim cno As New SqlConnection
[code]....
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May 24, 2011
I have some MS SQL field with NULL value. when i am trying to use below in VB.NET code no result comming...
1- dim sqlq as string = "Select * from table where name3 = null and address3 = null"
2- dim sqlq as string = "Select * from table where name3 = '' and address3 = '' "
But if same query # 1 i run direct SQL Query browser it works well.
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May 24, 2009
I've got a subquery that returns the most recent value from a child table. In some cases the subquery returns nothing. The query below fails at runtime because the inferred type of MemberPrice is decimal and is not nullable. [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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Jul 17, 2011
On a ASP.net form, I need to add a textbox to update a date field in MS SQL server via stored procedure. I want to verify user input cant figure out the correct syntax to do so (please see below)
If d.Text <> "" Then
cmd.Parameters.Add("@date", SqlDbType.DateTime)
cmd.Parameters("@date").Value = Date.Parse(d.Text)
[Code].....
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Mar 30, 2011
I need to round and print a price like below, but this does not handle null values.How can I handle null values on one line of code? DBRSet is an SQLDataReader and the price is money
<%= Math.Round(DBRSet("price"))%>
I have about 200 .aspx pages of this so I could also use some tips on how to change these in an easy way? Can I do a search and replace with a reg-exp or something like that?
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Jun 11, 2009
In a WinForms app (VS2008 / .Net Framework 3.5) I bind data from SQL Server to controls. If there's a null value e.g. an employee has no middle name (allowed by business rules), when I browse that record at runtime an exception is thrown. So I code: If Not (row("middle_name") Is DbNull.Value then txtMiddleName.DataBindings.Add(New Binding("Text", row, "middle_name)). Say someone adds a middle name to this record, because the control had no databindings the dataset.HasChanges property is false and update stored proc doesn't run. I guess I could handle this like this: If txtMiddleName.Databindings.Count = 0 AndAlso txtMiddleName.Text <> "" Then row("middle_name") = txtMiddleName.Text. I guess I would have to do something similar to handle a value changing from not null to null.
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Feb 16, 2011
I have run into this problem a few times and have never come up with a good answer. I figure others must have dealt with this already.I have a datareader returned from the database and I want to use the values therein however values may or may not contain NULL. I would like to have a unction that takes in the value from the datareader and returns the value if it is not NULL and blank space if it is NULL.The problem I have is that the data-type of the variable I am testing is variable. It can be a String, and Integer or a DateTime. Can anyone suggest a simple way to test the value and then return the original value (as same data-type if possible) or something else if it is NULL
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Apr 22, 2011
I am using KeyPressEventArgs to restrict several text boxes to numeric entries only. Rather than repeat the code, I thought I would make a "RestrictToNumeric" subroutine and call it from each "KeyPress" event. Like So:
Private Sub txt1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles txt1.KeyPress
RestrictToNumeric()
End Sub
[code].....
The problem I am encountering is that the variable 'e' is used before it has been assigned a value, causing a null reference at runtime.
So I tried to add Dim e As System.Windows.Forms.KeyPressEventArgs As?to the RestrictToNumeric sub.I cannot figure out what I need to "Dim" it as...
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Apr 18, 2011
I am reading dates from a table in a database to display in a DataGridView column that is formatted as a date. The problem is that when the value is null in the database my program errors out because it cant convert the value to a date. How do you guys handle this? *Edit: If I set the value of my date variable to "Nothing" it displays as "1/1/0001" in my DataGridView, and I would like the cell to be empty for the null dates.
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Aug 27, 2009
I have an RDLC report that I am rendering directly to the Response Stream as PDF (rather than using the ReportViewer). In the code that renders the report, it's DataSource is bound to a List(Of ClassA) objects defined in a custom assembly. This seems to work for the most part. My problem is that I can't seem to handle the situation where a nested object is null. For example, given ClassA and ClassB (the nested object) defined as follows:
Public Class ClassA
Public Id As Integer
Public Name As String
[Code]....
the report displays "#Error" if TheNestedObject is null. If TheNestedObject is not null, it correctly displays the Name.
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Dec 15, 2011
I have a fairly simple piece of code:
Private _PurchaseDelivery as PurchaseDelivery
Protected Overrides Sub InsertItem(ByVal index As Integer, ByVal item As PurchaseDeliveryItem)
[Code]....
Which is inside a class which overrides a custom list base. The code is occassionaly throwing an unhandled exception, System.NullReferenceException, on this line when used in production:
If _PurchaseDelivery IsNot Nothing AndAlso _PurchaseDelivery.DefaultSKUBinID.HasValue Then
DeafultSKUBinID is declared as an Integer? (Nullable Int) in the PurchaseDelivery class. I cannot see what might be causing this error, why would this be returning an error?
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Mar 23, 2009
I wrote an application to handle a joystick with directinput. It works fine if it uses the handle of the main window but it doesnt happen the same if the handle is the one of the component that contains the joystick's operation.
I mean:
main form handle: 15
component handle (which is inside the window and the joystick needs the focus of this component to work): 25
It always work if the handle i initilizate the device is the main form (15).How can i use only the handle of the component?
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Jul 15, 2011
How to check whether a column is null i use the following code but I got this error "Input string was not in a correct format."
[Code]....
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Aug 12, 2009
When I put a break point to the last if clause in the sub ("If (backOrder < 0) Then", see below) it runs until the break point, if I put the break point further below, I get the following error:
Cannot insert the value NULL into column 'OrderID', table 'WHM.dbo.OrderDetails'; column does not allow nulls. INSERT fails. The statement has been terminated.
I've discovered first hand that it only happens when prodqty is bigger then qtyOnStock, thus executing the if clause.
The code:
Private Sub NCOSubmit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles NCOSubmit.Click
Dim sqlText As String = ""
[Code]....
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Oct 20, 2011
I am trying to create a treeview in VB.net, the data has to be loaded from MSAccess 2010 database. When I try to run this program I get error : Argument Null Exception was unhandled, 'column' argument cannot be null and the program crashes. I have pasted the code as under:
Imports System.Data.OleDb
Public Class frmRating
Private Sub frmRating_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles
[code].....
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Jun 24, 2010
I have some code which gets child items for a menu via the GetChildren function which takes a list of menuData: Dim builtMenu As New List(Of MenuData)(_rawData.FindAll(Function(item) item.GroupingID = 0))
For Each menuData As MenuData In builtMenu
If menuData.Children IsNot Nothing Then
menuData.Children.AddRange(GetChildren(menuData))
End If
Next
If I check if menudata.children isnot nothing, it always is nothing because the GetChildren function is yet to run (providing the child items, which do exist). If I remove this check and just have this code:
Dim builtMenu As New List(Of MenuData)(_rawData.FindAll(Function(item) item.GroupingID = 0))
For Each menuData As MenuData In builtMenu
menuData.Children.AddRange(GetChildren(menuData))
Next
Then I am presented with a Object reference not set to an instance of an object error on menuData.Children.AddRange(GetChildren(menuData))
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Jul 25, 2011
Possible Duplicate: Can .NET intercept and change css files?
I have configured IIS6 to get .NET to handle css files.I did the following steps
Launch IIS Manager Right-click on Default Web Site Click on the Home Directory tab Under Application Settings click on Configuration.Add a new association for .css and map it to .NET executable:
C:WINDOWSMicrosoft.NETFrameworkv2.0.50727aspnet_isapi.dll
How can I check if this is working, i.e. I want to change the default style of a page depending on the url, i.e. if the referer url is http://intranet, it should continue to use the old existing style style1.css, if the referer url is http://intranetv2, it should use the new style style2.css.
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Aug 6, 2009
I can't get a handle on the syntax. Can anyone give me a simple demo?
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Jul 2, 2009
I am trying to get a handle on the correct way and easiest way to do things. By easiest I am not talking about being lazy just accessing and modifying later on. I have started using my own classes and such but I have a few questions. Sometimes I want to create a control on the fly through code instead of using the designer. Should I create this control in the main form file or in a separate class? If I make it in another class it seems harder to access later on. Then again if I dont know that the control is going to be created(user clicks a button to add a control) how can I access it? Also it seems alot harder to access certain things when it is in another class. For example if I create a new window in a class and then want to check if it is there or not it is alot harder to do.
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Feb 13, 2012
Are there anyone know how to get the handle of a standard Combobox using API?
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Dec 13, 2011
How do i get the handle of a NotifyIcon?
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May 8, 2009
I need the intPtr for a form. Control.FromHandle(control) gives me the control from a handle, but I need the opposite--get the handle from a control. How do I do this?
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Apr 27, 2009
I need to get the handle of a control as an IntPtr to pass to a screen capture class in vb.Net 3.0. Tried this but get an invalid handle exception.
Dim hwnd As IntPtr = Runtime.InteropServices.GCHandle.Alloc(CanvasMap)
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Jan 24, 2012
I am trying to create a small utility that tracks desktop usage in detail, to the level of individual text boxes etc.... in other applications. However, it is proving quite tricky. I thought I had it nailed using the Windows api. The below code is just a snipet of the code but essentially it provides me the handle of the control that the mouse is over. I thought from here, it would be easy to to the same thing but to provide the handle of the control that the cursor was actually clicked on, for example, if someone is filling in a text box in an application, they would not necessarily move the mouse to get to the text box, they may tab to it. Does anyone know if there is a way to get the handle of the control that is in use?
Private Sub Timer1_Tick(sender As Object, e As System.EventArgs) Handles Timer1.Tick
Dim ptx As Integer = Cursor.Position.X
Dim pty As Integer = Cursor.Position.Y
[code]....
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Apr 12, 2011
I need to get the handle of a window with a specific name from my vb.net application. The form isn't actually from my application.
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Jun 23, 2009
I am going mad about getting the process id for one existing handle on VB2008.I tried both GetWindowThreadProcessId(hwnd, pid) and GetProcessId(hwnd), while PID always returns 0, I tried the same things in VBA of Excel, it works perfect, so this is somewhat weird,
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Jun 22, 2010
I have referred DLL in my project. I have to handle the event from DLL in VB.net code. I guess we can do using WithEvents. Can you give me complete picture?
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May 6, 2009
I am having a SP run in my VB application every 10 seconds to check for any new rows that have been inserted to the database since the last check. What is the best way to do this? Most likely it will be 0 or 1 rows, but I am afraid at random times it maybe more than 1 and so I thought I would fill it in a DataSet, but I came in here to see if there are any other better ways. If dataset is the best way, how do I do a For Each Row in the dataset to process some VB code for each row?
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Sep 12, 2009
The short program below runs just fine when it is the only item on a form. However, when I put it into the ItemInsertTemplate of a ListView control, I get the following message:
Handles clause requires a WithEvents variable defined in the containing type or one of its base types
Line 30: Protected Sub btnDate_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnDate.Click
The error message identifies Line 30 as the problem.I get the same message for Sub clnEvent_SelectionChanged How do I correct this?
<%@ Page Language="VB" AutoEventWireup="false" CodeFile="clnControl.aspx.vb" Inherits="clnControl" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
[code].....
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