Asp.net - Check If A Checkbox List Item Is Checked/unchecked?
May 14, 2012
I have a checkbox list which is filled with entries from my database on page load. I need to update an entry in my database when a item is checked and when an item is unchecked. Right now I am doing the following:
<asp:CheckBoxList id="check1" AutoPostBack="True" TextAlign="Right" OnSelectedIndexChanged="Check" runat="server">
</asp:CheckBoxList>
And the function:
Sub Check(ByVal sender As Object, ByVal e As EventArgs)
Dim sql As String
If check1.SelectedItem.Selected = True Then[code]....
The error is: "Object reference not set to an instance of an object." Is there a better way to check if a list item is checked or unchecked?
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Mar 3, 2012
I want to create a solid checkbox that is checked by default, and is not clickable. If you click it, nothing will happen . how to do this?
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Jan 8, 2011
The check box list has an event called "ItemChecked" or something, which triggers when an item is about to change its checked status.
So, it is before the check occurs.I couldn't find an event that occurs after the item has changed.. I want to execute some code only when an item is checked or unchecked.
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May 16, 2011
My form contains a combobox which contains several usernames which are bound to my database.I've added a checkbox to the form which will be used to select the default username from the list.
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Mar 29, 2012
I use a textbox for input unless one of the checkboxes is checked, then the textbox needs to have a value of 1 which I have working.What I need is a way to lock the textbox if the checkbox is check and allow data if it is unchecked.[code]
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Aug 17, 2010
so im dynamically populating a checkbox list. I have confirmed that my text and values are correct for each checkbox but when I check a few and click my event button when I loop through the items they are all set to select=false...
Dim resource As ListItem
Dim SelectedHashTable As New Hashtable
For Each resource In chkResources.Items
[code].....
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Oct 3, 2010
I have a datagridview with a checkbox column.i want to check whether checkbox is checked or not.If the checkbox is selected it should output as "True" in messagebox and if checkbox is not selected it should giving me a message "False".
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Feb 24, 2011
I have about four columns inside my listview.I also have checkboxs that are located to the left of the listview. A checkbox is added to first column but how would I check if the checkbox is checked?
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Jan 16, 2011
I'm trying to see what checkbox is selected is checked
With this code.
[code]...
Unable to cast object of type 'System.String' to type 'System.Windows.Forms.CheckBox'.
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Oct 31, 2010
How can I check if there is at least one checkbox checked?
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Dec 30, 2010
How can i check if only the checkbox is checked without having the user select the node.
This code works, but the user has to check the itm first
If TreeView1.SelectedNode.Checked = True Then
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Jul 2, 2009
how do i make an event for only one checkbox in the checked list box ie there are 3 items
item A
item B < this one needs to have the event...
item C
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Jul 15, 2010
I have the following update command which needs to be amended, I want before the query to check if chkactive checkbox is checked or Not, if checked then True value to be added to the tblProjects otherwise if unchecked False to be added.
[code]...
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Jun 30, 2009
I've got a form with parent-child setup. The parent displays name and other demographic info.The child displays multiple addresses, one row at a time. There can only be one primary address for a name and this is designated by a checkbox at the top of the child form.If the user wants to change the primary address to another address,then they find the other address and click on the checkbox.The form checks the other addresses and if one is found that is designated as primary,the user is warned that one already exists and prompts them to change it.
So for example, a name has 2 addresses, the 2nd being the primary address.The user wants to change the 1st address to be primary.They click on the Primary Address checkbox for the 1st address.A warning displays that there is already an address listed as primary.The user then answers the prompt to change the 1st address to the primary address.The checkbox for the 2nd address will be unchecked and the checkbox will be checked for the 1st address.My problem is getting the checkbox unchecked for the 2nd address.If I close the form and reopen, then the checkbox is unchecked.How do I refresh the checkbox for the 2nd address?Here is the code I'm using to find if an address has already been marked as primary:[code]......
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May 19, 2009
I have a chechlistbox and i have 10 items. and items are checks randomly.
i want to determine which items in checklistbox is check.
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Oct 9, 2009
How to make every checkbox in a checked list box (VB 08) generate its own click events .
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May 28, 2009
I have this code:
Code:
Private Sub CheckBox1_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CheckBox1.CheckedChanged
If CheckState.Checked Then
AmxModXInstallDir.Enabled = False
Button1.Enabled = False
[code]....
When i check the box, it enables all controls, if i uncheck it, nothing happens.
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Apr 28, 2011
from the code below I am trying to find out if checkBox1 is Checked or Unchecked. and then I want my settings to remember if it is checked or unchecked. so when the form is loaded I want my settings to load the last action.... ie checked or unchecked.
so if a user check's the checkbox1 then the message will not show, But if it is unchecked the the messageBox will be shown
Private Sub CheckBox1_CheckedChanged(sender As System.Object, e As System.EventArgs) Handles CheckBox1.CheckedChanged
If CheckBox1.Checked = True Then
[Code]....
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Apr 12, 2011
Does anyone know of a control such as a Checked List Box where each item can have a value against it.For example you have a list of fruits and in the listbox it displays Apple, Orange & Banana but the values for those items are A, O & B.
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May 11, 2009
I'm having a hard time figuring out why this is happening. When I check an item in the listbox it calls the sub ItemCheck for the listbox accordingly:
Code:
Private Sub chklbToDo_ItemCheck(ByVal sender As Object, ByVal e As System.Windows.Forms.ItemCheckEventArgs) Handles chklbToDo.ItemCheck
Dim iLoop As Integer
Dim iCheck As Boolean
[code]....
I've had to work with the delay of the check by reversing the boolean value caused by the check. But when I worked it into the program to delete the item that is checked, it deletes the selected/(un)checked item and THEN checks the item with the index. So in other words, if a user selects and checks an item in the listbox, and chooses to delete the item, it deletes the item and then checks the item that replaces it in the index (the following item).I don't understand why the checked value doesn't appear until after the sub ends.
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Mar 14, 2009
In Vb.net 2005 how can i trap the checked/unchecked state of a datetimepicker through an event. I'm trying to execute two different methods based on the checked/unchecked state of a datetimepicker when the user clicks the datetimepicker. When the user checks the dtPicker Method A is executed, when the user unchecks it Method B is executed. How can i trap it.
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Jan 11, 2011
So I'm trying to figure out how to correctly override GetHashCode() in VB for a large number of custom objects. A bit of searching leads me to this wonderful answer.Except there's one problem: VB lacks both the checked and unchecked keyword in .NET 4.0. As far as I can tell, anyways. So using Jon Skeet's implementation, I tried creating such an override on a rather simple class that has three main members: Name As String, Value As Int32, and [Type] As System.Type. Thus I come up with:
Public Overrides Function GetHashCode() As Int32
Dim hash As Int32 = 17
[code]....
Problem: Int32 is too small for even a simple object such as this. The particular instance I tested has "Name" as a simple 5-character string, and that hash alone was close enough to Int32's upper limit, that when it tried to calc the second field of the hash (Value), it overflowed. Because I can't find a VB equivalent for granular checked/unchecked support, I can't work around this.
I also do not want to remove Integer overflow checks across the entire project. This thing is maybe....40% complete (I made that up, TBH), and I have a lot more code to write, so I need these overflow checks in place for quite some time.
What would be the "safe" version of Jon's GetHashCode version for VB and Int32? Or, does .NET 4.0 have checked/unchecked in it somewhere that I'm not finding very easily on MSDN?
EDIT:Per the linked SO question, one of the unloved answers at the very bottom provided a quasi-solution. I say quasi because it feels like it's....cheating. Beggars can't be choosers, though, right?
Translated from from C# into a more readable VB and aligned to the object described above (Name, Value, Type), we get:
Public Overrides Function GetHashCode() As Int32
Return New With { _
Key .A = _Name, _
[code]....
This triggers the compiler apparently to "cheat" by generating an anonymous type, which it then compiles outside of the project namespace, presumably with integer overflow checks disabled, and allows the math to take place and simply wrap around when it overflows. It also seems to involve box opcodes, which I know to be performance hits. No unboxing, though.
But this raises an interesting question. Countless times, I've seen it stated here and elsewhere that both VB and C# generate the same IL code. This is clearly not the case 100% of the time...Like the use of C#'s unchecked keyword simply causes a different opcode to get emitted. So why do I continue to see the assumption that both produce the exact same IL keep getting repeated? </rhetorical-question>
Anyways, I'd rather find a solution that can be implemented within each object module. Having to create Anonymous Types for every single one of my objects is going to look messy from an ILDASM perspective. I'm not kidding when I say I have a lot of classes implemented in my project.My final implementation, which fits the constraints of GetHashCode, while still being fast and unique enough for VB is below, derived from the "Rotating Hash" example on this page:
'// The only sane way to do hashing in VB.NET because it lacks the
'// checked/unchecked keywords that C# has.
Public Const HASH_PRIME1 As Int32 = 4
[code]....
I also think the "Shift-Add-XOR" hash may also apply, but I haven't tested it.
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Jan 17, 2009
i need a little bit of help with the checkedlistbox. What i want to do is add a phrase or a reminder and if i check the checkbox of that item, i want the text to be strikeout (the text with a line in the middle) and when the form closes i want it be removed from the checkedlistbox.
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Sep 30, 2011
I want to check a checkbox of the selected item in a checkedlistbox but option strict disallow it. How can I do it without turning it off?
Dim clb As CheckedListBox = DirectCast(sender, CheckedListBox)
clb.SelectedItem.checked = True 'late binding error
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Apr 5, 2010
How can I get all the selected values from a check list box? I tried using the name of the check list box (clbLike) but it only returns the first value checked. How can I return all values checked?
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Aug 11, 2009
[code] I am trying to append the name of each checked list box item selected to the end of the current directory but i am obviously doing something wrong.
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Jun 3, 2011
I have a Main form, called Main.vb, that is a Parent Form. I have another form called Notes.vb. Inside Main.vb I have a toolstrip with a button on it called Notes. I'm wanting to change the checked status of the Button to either True when the Notes.vb window is open inside the parent or to false when it is close. Is this possible?
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Mar 14, 2009
How can i trap the checked/unchecked state of a datetimepicker through an event. I'm trying to execute two different methods based on the checked/unchecked state of a datetimepicker when the user clicks the datetimepicker. When the user checks the dtPicker Method A is executed, when the user unchecks it Method B is executed. How can i trap it.
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Sep 12, 2011
ok so the data grid view idea was rejected.
what im working on now is a
checkedlistbox and a listbox
the data on the checkedlistbox are coming from the database
(how do i get the mat_id but just display mat_name only?)
[Code]...
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Oct 3, 2010
I have a very stubborn check box . Let me tell you its story :There is Form1 with a button leading to Form2 . On Form2 there is located that stubborn check box I was telling you about . That check box has code in its CheckedChange event and accordingly to its Checked condition , it enables or disables some text boxes .Well , the first time Form2 is shown , that check box works fine : when I check it it enambles the text boxes and when I uncheck it , it disables those text boxes .Then , I press the button to return to Form1 . If needed , the code in the button is :Form1.ShowMe.CloseMy adventure starts when I show again Form2 ... This time the check box is acting weirdly . No matter if I check it or I uncheck it , it always disables the text boxes , as if it is constantly unchecked ! I can see it changing its checked state whenever I click on it , but it always runs the code to disable the text boxes.
I even used some break points in the code and found out that indeed it is the code that disables the text boxes that is called every time , no matter if the check box is checked or unchecked .I don't thing this has anything to do with the fact that this event is called by all the 4 check boxes on the form . After all , it is always the 1st check box that causes the problem (I can see it when moving the cursor over the genericindex variable) .
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