Null Value Of Combobox?
Mar 10, 2010
I have two combobox on which will display company and department names. There is a"SelectedIndexChanged" event for company combobox. I don not want that is triggered when value of combobox are empty or null. I tried CompanyCombobox.seletedValue is not null and other ways, but they were not working. How do I detect there is empty or null value on combobox?
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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 22, 2012
I'm using vb.net and sql server 2000 for developing my application....The problem i'm having is the Null Reference Exception on the Following line of code:
Dim cmd5 As New SqlCommand("select crtns_removed, pieces_removed, scheme from Outgoing_Invoice where invoice_no = '" & Me.ComboBox5.SelectedItem.ToString.Trim & "' And category = '" & Me.ComboBox1.SelectedItem.ToString.Trim & "' and item_name = '" &
[code].....
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Nov 16, 2010
I have a combobox with a dropdownstyle of dropdownlist (style 2). When a user finishes making entries and clears the form, I want the display value of this to return to null. With an unrestricted combobox, I could just set .text="" and be good to go; that doesn't work with the ones that are restricted.
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May 18, 2010
I tried binding data to combobox at the runtime in the form load event. I had written the following bind function,
Private Sub BindComboBox()
Dim da As SqlDataAdapter
Dim conn As SqlConnection
Dim ds As DataSet = Nothing
[code]....
The problem is cboSubject.SelectedText is returning empty string.
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May 27, 2012
y code below:
Function combobfill(ByVal table As String, ByVal field As String) As DataTable
addconnection.Open()
Dim selectstring As String = "select " + field.ToString() + " from " + table.ToString()
[code].....
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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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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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Jan 27, 2010
I am using VB.NET together with ADO.NET to create a program. I have set my TableAdapters as needed and bound the correct tables-columns to my comboboxes.My problem though is this:My combobox2 item is bound to a datatable. The table adapter's Fill method (the select command basicaly) includes a public variable in the where clause to fetch the correct results. I ll put some code here to clarify it a bit more.Public Class Frm_inv
[Code]...
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Feb 20, 2012
I have a tab control application, each tab loads a particular user control and each of those user controls will then add other user controls that are used amongst other the user controls. For example, I have an "ucQuotes" page and an "ucInventory" page, when the specific tab is selected, the "uc****" user control is loaded on that page, and in the case of "ucQuotes" and "ucInventory" they both use a control called "ucPartNumber"; a user control consisting of a combobox, textbox, and button. I have no issues reusing the shared user controls, in this case. My problem arises with my "ucQuickPrice" control, as it is always present at the bottom of the tab control form (separate from the tabcontrol, but on the same form), and it too uses ucPartnumber.
Here's my issue, as I type into the ucPartnumber combobox, the text I type does not appear in the combobox, it appears in the textbox of the ucPartnumber control that is being used on the tabcontrol page. There are no shared instances of ucPartNumber, nor do I have this issue between typing on one tab page and the text showing on the user control of another tab page.I tried just creating the ucPartNumber controls on the ucQuickPrice control, not adding a new instance of ucPartnumber on the .Load event, and the issue persists.
The combobox(s) in question are bound programmatically with about 40,000 items, ".datasource = dataset.tablename" not to a bindingsource. Autocomplete is set to none, I added code to utilize tool tips and the basic combobox filtering functionality. Is this a bug, or is there something I'm neglecting? I'm about 95% complete with this application, and this just happened today. I made the decision, to just reuse the ucPartNumber control on the ucQuickPrice control (originallly it's size and orientation would not fit, but I added some coding to detect what parent is adding ucPartNumber and to change its appearance accordingly). Before, I made this change, I did not have this problem. And, in trying to go back to how I had things set up before the change, the problem will not go away. if the whole control within a control verbage I used is a bit confusing, let me know and I'll try to better explain what is happening. At this point, I'm going to close and reopen vbexpress, as when I started this ordeal, vb started acting weird and wanted me to save all my work, it usually does this before locking up.
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Jun 17, 2011
I am new to vb.net and I am using visual studio 2010. I have two comboboxes on a form, each combobox is set to DropDownList so that a list of items can show in the combobox, but no text is allowed to be entered.
For combobox A, if user chooses item 1, the list of combobox B should be updated accordingly. I think this is quite common on a lot of applications. But I do not know to implement it. I even do not know the keyword to search for the relevant property or event handler.
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Aug 10, 2009
I had added the items
1
2
3 to the combobox.
Then I gave the "Select" to the text of the combobox.
How can I able to reset combobox to select the text("Select").
I had tried by giving -1 to the SelectedIndex. But it gives only Empty.
This is for VB.NET Windows Application
I have given an Image for your reference
Image path for the reference [URL]
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Mar 26, 2011
When I will click the suggested text shown in the combobox it will disappear.My Combobox btw is connected in a database.If I type Kev then kevin and kevsky will show at its suggestion then when I will click any of it ,the combobox text will be empty or will clear what I typed ("Kev") and will not show what I clicked.[code]
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Aug 11, 2009
I had added the items 1 2 3 to the combobox.
Then I gave the "Select" to the text of the combobox.
How can I able to reset combobox to select the text("Select").
I had tried by giving -1 to the SelectedIndex. But it gives only Empty.
This is for VB.NET Windows Application
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May 3, 2011
I am making a custom ComboBox, inherited from Winforms' standard ComboBox. For my custom ComboBox, I set DrawMode to OwnerDrawFixed and DropDownStyle to DropDownList. Then I write my own OnDrawItem method. But I ended up like this:
How do I make my Custom ComboBox to look like the Standard one?
Update 1: ButtonRenderer After searching all around, I found the ButtonRenderer class. It provides a DrawButton static/shared method which -- as the name implies -- draws the proper 3D button. I'm experimenting with it now.
Update 2: What overwrites my control?I tried using the Graphics properties of various objects I can think of, but I always fail. Finally, I tried the Graphics of the form, and apparently something is overwriting my button.
Here's the code:
Protected Overrides Sub OnDrawItem(ByVal e As System.Windows.Forms.DrawItemEventArgs)
Dim TextToDraw As String = _DefaultText
__Brush_Window.Color = Color.FromKnownColor(KnownColor.Window)
[code]....
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May 2, 2012
DataGridView TIPs has TextBoxes and ComboBoxes in it and the data comes from an SQL table. I see how to get or set the cell values that come from the ComboBoxes using Item, but how do I access the actual ComboBox events and properties?
[Code]...
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Sep 28, 2011
I have a table in my database with 5 columns (ID1 to ID5) and just one row. I'm trying to bind a comboBox, to show ID1 through ID5 in the combobox when my form loads. I have a dataset and tableAdapter's made for this already. I just want to know how to bind a combobox to those ID values.
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Jun 14, 2011
[Code]...
I'm making a combobox on a form. I want the combobox to have a list of choices from a table in a db. The two columns are a String and a Date. I want the date column to only show the year. I'm hoping I have the code right as it is above, but I'm not positive I've done the whole date thing right.
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Oct 19, 2010
I think my question is discriptive, or as Microsoft in the Documentation for Data Grid the question is, How do I have a combo box column display a sub set of data based upon the value of a different combo box column?
[Code]...
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Jun 19, 2009
I have a combobox..... When a user clicks on the list inside the combobox my webbrowser opens to the selected items website.how to make the combobox go back to the original text of the combobox?
Example: Combobox list
---- Select Item ----
Royals
Mets
[code]....
When the user see's the screen the ---- Select Item ---- is visible. When a user clicks a teams name it opens the teams website and the name stays in the box. I want it to go back to ---- Select Item ---- immediately after they click a list item.
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Mar 27, 2011
Is there a way to update source combobox to printer combobox selection?So going from printer1 to printer2 the source will update according to what that printer has to offer.
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May 13, 2009
I have completed my project and i have one remaining thing to settle... I want to make the combobox not to be able to write yourself. for example there are 4 options ,"A","b", "c","d".If i type w in the combo all the project is ruined!i want not to be able to type at all to prevent this...Which property should i change?
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Feb 22, 2012
I'm having a problem with combo boxes. I usually use Java and it's been awhile since I used VB but I never remember having this much difficulty.My application is using an SDF file. From Data Sources, I drag the details on one of my Tables to my Form to get all of the fields. Three of them are comboboxes. Each of the three is an INT64 and each corresponds to a primary key in a different table. I click the tasks button on a combobox and for data source I select the appropriate table that has the data to go with the combobox, for display member I select the field that I want users to see, and for value member I select the primary key. Then I run a quick test and start the app, open the form, and add a new record. When I select a value from the combobox the selection won't validate because it doesn't think it's an INT64 like it should be. It seems to be using the display member as the actual value instead because if I change display member to the primary everything works great.
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Sep 23, 2009
have build some code which goes through the datasource finding records on what a user types, basically if the user types 'P' in the combobox it finds all records from FieldName with 'P' and if you type 'Portugal' it finds all records from the FieldName with 'Portugal, it all narrows down the search list say if there are to entries which match 'Portugal' the combox would only have to items in. The problem i am have is that when i bound the datasource back to the combobox every letter you type stays at Postion 0 of the combobox and doesn't move to the end of the letter as normally the combo works, does any one now how to get arround this problem.
At the moment i call my combobox search code from the keypress event of the combobox.This code works fine with recordsets in msaccess combobox but i cannot get it to work with the datasource of the combobox in vb.net Heres the code from the combobox keypress event:
Private Sub ComboBox1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles ComboSearch.KeyPress
Dim keyascii As Integer = AscW(e.KeyChar)
PhoneBookComboSearch(keyascii)
End Sub
Below is the code at the end of my keypress event send the datasource back to the combobox.
Dim adapter As New SqlClient.SqlDataAdapter(strSQL, conn)
Dim dt As New DataTable("MyTable")
Dim ds As New DataSet
[code]....
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Jun 5, 2011
Private Sub AddIngoing_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
[Code]...
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May 10, 2011
I need to give a user a drop down list of items to choose from, but I dont want them to be able to type in the combo box, any ideas?
[Code]...
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Dec 15, 2011
I have cascading comboboxes and when I choose the value for the first one everything is fine. But when I try to choose the value for the second combo the value of the first disappears. However, the second combobox is populated with the appropriate values and then I have to choose again the value for the first one. This is the code:
For the fisrt Combobox
Dim PostcodeDA As New SqlDataAdapter()
Dim PostcodeTable As New DataTable
[code]....
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