I get the following error message when entering edit mode on a DataGridViewComboBoxCell:
System.NullReferenceException was unhandled Message=Object reference not set to an instance of an object.
Source=System.Windows.Forms
StackTrace:
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Using VS2010 and VS2008
I have a DataGridView bound to a DataTable which has an Int16 DataColumn. The DGV has a DataGridViewComboBoxColumn tied to the DataColumn.
I enter integer values in the Items section of the DGVCBColumn properties. When I run the program I get "DataGridViewComboBoxCell value is not valid".
I assume this is because my Items are text and the data column is integer so I created a List of Integer, added my integer values/choices to the list and made the List my data source for the ComboBox column. Same error.
I then created another DT in the DS with one column type Int16, added my integer choices to the DT, created a BS for the ChoicesDT and set this BS as the DataSource, the column as the DisplayMember and the ValueMember. Same error.
There are no issues like this when the DataColumn is bound to a ComboBox outside of the DGV so I assume there is some issue with the DGV understanding the underlying binding.
I have a datagridview and a column which is DataGridViewComboBoxCell
I want to set datasource for that DataGridViewComboBoxCell?
The problem I have now is that I can not get the value selected as a combobox, I'm trying to set the text and value to each item in the combobox of each cell in the datagrid.
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On a form I have a DataGridView. Inside this DataGridView i have several columns of which one is combobox and the others are textboxes.The combobox column is populated with values from a MySql database table using a query. So far so good. What i want next is to populate a certain textbox from that DataGridView, automatically after a value from the combobox is selected. When a value is selected from the dropdown list of the combobox, that value is used in a SQL query to find the value that will be displayed in the textbox.All the textboxes and the combobox are inside the DataGridView!)I did this using DataGridView EditingControlShowing event because a DataGridViewComboBoxCell does not have aSelectedIndexChanged event.The value is displayed correctly in the textbox, but the problem is that the value selected from the combobox disappears after the selection, and the combobox remains empty. I need the value to remain in the combobox after it was selected and after the corresponding value was inserted in the textbox!Here is the code for this:
Code:
Private Sub test_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
'Populating the combobox
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I have come accross many scenarios of handling datagridviewcombobox events, however none seem to fit my scenario, or I may be missing something.1. I need to capture the column index that the combobox is resident in. This is because I have a complete row of comboboxes that should set the header text to the selected value.here is the code I have so far:' I also use a list of string as datasource publicly declared
Public cs As New List(Of String)
'to insert the combo's into the grid
Dim row As New DataGridViewRow
cs.add("Book")
cd.Add("Author")
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[URL]..But I can't design a solution. Could anyone try to help me out here? I know there are some workarounds to be found, but either the links are dead (check above link) or it's writter in a language I still can't read. Here's my code.
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I have a DataGridView with two DataGridViewComboBoxColumns. I want to use the selected item in the first column to trigger a re-population of the items in the second column, on a per-row basis.
Here's the code I have so far. "addlInfoParentCat" identifies the first column, and currentRow.Cells.Item(1) is the DataGridViewComboBoxCell that I want to re-populate. ExtEventAdditionalInfoType is a type I defined that contains the string/value pairs.
Private Sub dgvAdditionalInfo_CellValueChanged(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewCellEventArgs) Handles dgvAdditionalInfo.CellValueChanged
Dim currentCell As DataGridViewCell
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I want to have a DataGridView that has two columns.The first column will always be of type DataGridViewComboBoxColumn. Based on the selection in that column, I'd like to be able to change the corresponding cell in the second column to either a DataGridViewComboBoxCell or a DataGridViewTextBoxCell.I'm thinking I just need to make the second column of type DataGridViewColumn, but don't understand the mechanics of how to change the cell type on the fly.I'm working with VB.NET in Visual Studio 2005.
Update: One way around it, I suppose, is to make the second column as a DataGridViewComboBoxColumn, and change the attributes of the cell so that it either behaves like a drop-down list, or as an (editable) drop-down with no elements. The latter looks enough like a text box that I could live with it, and it wouldn't involve changing the type of the cell.
I'm getting some data from a database and I'm setting them to a DataGridViewComboBoxCell. I also need to set the Tag property of each DataGridView ComboBoxCell item to a specific value, so later, I can query the DB with those two items.The issue, is that I can't seem to figure out how to access the DataGridViewComboBoxCell Item's Tag property.[code]I wrote it on the spot and it wasn't until later that I realized that I'm setting the Tag property of the DataGridViewComboBoxCell itself and not the DataGridViewComboBoxCell's Items.
View 7 RepliesHow do I set SelectedIndex of a DataGridViewComboBoxCell?The code fill the combobox with items, but I need to select one of them My Code:
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DataGridViewComboBoxCell Tag cleared in EditingControlShowing event?
View 2 RepliesI have a TextBox column in my DataGridView. When the user clicks one of the cells in the column I turn that cell into a DataGridViewComboBoxCell and fill the items using the columns Tag property which is a 1-dimensional array with 3 items. This is what my Tag looks like:
?CType(sender, DataGridView).Columns(e.ColumnIndex).Tag
{System.Array}
(0): ""
(1): "No Reportable Result"
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I am using VB 2010 Express to create a windows forms application with an unbound DataGridView. The DataGridView has multible columns, two of which are ComboBox Columns. I would like to make the borders of the cells be bold when selected as some type of indication to which cell is the current cell. It is possible that I overlooked something completly but I could not seem to find a property that would allow this to happen.
My solution was to create a custom class which inherits from the appropriate DataGridViewCell type (e.g. DataGridViewTextBoxCell, etc..), in that class I override the Paint sub. There I check the selected property and draw a rectangle using the cell bounds.
This works with every type except the DataGridViewComboBoxCell. On the columns of this type I receive an ArgumentException on the call to the Paint Sub. Even if I just have an empty class that only inherits from the DataGridViewComboBoxCell.
Again, it is quite possible that I have overlooked somthing and am making the a lot more complicated than it needs to be.
i encountered a problem but this happened on the client side. In my PC, i don't encounter this error.
The error is: System.argument datagridviewcomboboxcell value is invalid
Is there anyone who encountered this problem? Could the client's PC needs updating on a certain dot net fix?
I have an error but will explain how i set up my db:Two tables, One is called Area and the other Postal_Code.
The aim is to assign a postal code to the area.Sometimes we add postal codes and sometimes these codes change or need to be deleted.I used the wizard to create the datasets and dropped them on two forms linked to a SQL db.We can Add,Edit,Update & Delete so all is working fine there is no relationship between te tables as they dont need to be linked, I only require the PCode to me added to the Area Table, not any ID or Index etc.
One of the fileds in the Grid on the Areas form is the Postal Code, its set to a combobox that when the user is adding it gives them a selection of postal codes to select from.I get the error when loading the datagrid on the Area form: System.ArgumentException: DatagridViewComboBoxCell value is not valid
This happens only when the postal codes are changed or deleted in the Postal codes table.
I know what causes the error - the dropdown on my Areas form looks for the value in the Postal Code table and does not find it beacause it has either been changed or deleted.Im doing this manually - I go into SQL and remove the postal code data from the record.Then the form loads with no errors.
Q: Is there any way when the Datagridview loads that I can tell it when the PCode does not exsist in the Postal Codes table that it should rather leave it blank and warn the user that there are errors they need to fix befor they can save.
Given a datagridview, using complex binding I have a datagridviewcomboboxcolumn that displays data from a different table. My question is: when the dropdown list of the comboboxcell is shown is it possible to display a different text than the DisplayMember, lets say more detailed?I search for a solution but could not find any.
View 3 RepliesI have a DataGridViewComboBoxColumn, and want to switch the style of the ComboBox control between DropDownList and DropDown (mainly for the text field editing capability). I'd like to do this on a row-by-row basis (at the DataGridViewComboBoxCell level).How would I do that programatically? Or maybe a different way of asking: How do I access the ComboBox control given an object of type DataGridViewComboBoxCell?
View 1 RepliesI've tried pretty much everything to solve this problem (except what works, obviously) and almost worn out Google, so now I'm giving this forum a chance. Basically I'm making an application which needs to map column names in an excel spreadsheet to fields in a table (TableB) through a data transfer setup table(TableA); To make this work as planned, I need to compare a value in "FromField" in TableA with headers/column names read from an excel spreadsheet into a list of strings, and if they match, map "FromField" against "ToField", prior to importing data from the spreadsheet. The column names that don't match with "FromField" are to populate a combo box in the FromField column in my DataGridView.
PROBLEM: I get this to work fine as long as I don't handle case differences (e.g. "FieldToBeImported" in Field1 vs. "fieldtobeimported" as header in spreadsheet), but this prevents matching words with case differences to be mapped, and leaves it to the user to manually map fields that should have been mapped automatically. However, if I make a ToUPPER copy of the List Of String that contains the MS Excel column names and compare them to a ToUpper version "FromField" data, I get the error message from the topic:
"System.ArgumentException: DataGridViewComboBoxCell value is not valid"A little explanation on DataGridView2 before diving into the code: Column in index 0 is a DataGridViewComboBoxColumn added in code, where matching fields in column 0 and 1 are mapped, and non-matching fields are populated in the combobox.Column in index 1 is "ToField" (TableA as source), Column in index 2 is "FromField" (TableA as source) and is hidden in runtime.
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I use VS2005 and visual basic. I have a SaleDetail table has the following fields:
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I'm using this code:
Dim cListItems As New System.Collections.Generic.List(Of Combobox_values)
cListItems.Add(New Combobox_values("One", "1"))
cListItems.Add(New Combobox_values("Two", "2"))
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I have a Class MessageIndex which holds an integer. I have a custom DataGridViewComboBoxCell which has a MessageIndex variable. If the MessageIndex is not set, the cell acts as a normal DataGridViewComboBoxCell; if the MessageIndex is set, then the GetValue and SetValue methods of the DataGridViewComboBoxCell are overridden so as to return the value of the object from its DataSource at the index of the integer stored in the MessageIndex.
As far as I can tell from stepping through the code, that actually works fine. The object returned by the GetValue function is fetched from the DataSource, based on the integer stored in the MessageIndex.
The problem is that when the DataGridView is displayed, all of the cells are blank. The values of the cells can then be set using the ComboBox dropdown, which appears to work fine.
But why are the initial selections not being displayed? As I say, as far as I can tell, the correct information is being retrieved by the GetValue function of the DataGridViewComboBoxCells when the form is initially displayed. It's just not ending up on the screen.
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))
View 7 RepliesThis never happened to me, and the less data one has (usually) the less you can say what happened.I am trying to write a simple query analyser. I randomly receive these kind of crashes:
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The file specified above does not exist. The place where it crashes is wrapped with Try-End Try. Moreover, yes, I have the painting event set up but it should not concern it (or maybe it does?). I have to add that I use visual basic express edition. The error occurs ocasionally - sometimes when I'm lucky nothing happens, and when I'm not then I get this crash.
When I debug a program my IDE simply does not catch System.NullReferenceException - execution continues as if there were nothing wrong.Moreover, when I go to the menu Debug/Exceptions System.NullReferenceException is not even in the list(Common Language Runtime Exceptions).
I manually add it (there is the Add button) and I put a checkmark in the 'Thrown' and 'User unhandled' column - now IDE catches it, but after I re-load the project the situation re-appears - and NullReferenceException is not on the list again. What may be wrong?
Update:No, when I step through the code the execution does not continue but exits the current block of code (sub or function). There were no Try...Catch blocks and there is a message: A System.NullReferenceException occured in MSCorlib.dll... But why doesn't the debugger stop at this line?
How can I get a NullReferenceException in the following scenario?
Dim langs As IEnumerable(Of SomeCustomObject) = //some LINQ query
If langs Is Nothing Then Return Nothing
If langs.Count = 1 Then //NullReferenceException here
What am I missing here? Debug shows that langs is really just a LINQ queryresult without any results...
Okay after searching two listbox's on a form I am trying to put a number as a string in a label setup for that but keep exgetting a NullReferenceexception error on the label. Label being "shippingDataLabel.text".e is my code;
Public Class MainForm
Dim fifteenShipping As Integer = 15
Dim twentyShipping As Integer = 20
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I have a VB.NET solution that I just upgraded. It was originally in .NET 1.1, I upgraded to .NET 2.0 and verified that it would build and run correctly. Then I upgraded from 2.0 to 4.0. It is still building with no errors, but when I try to run I am getting a NullReferenceException in Global.asax.vb. The really weird thing is, the line that is throwing the exception is this:
Dim dt As System.Data.DataTable I am not trying to use the variable, just declare it. Further down a Function is called that returns a DataTable and sets the variable, but I don't even get to that line. It is throwing the NullReferenceException on the Dim line. Has anyone run across this before? Is this some issue with upgrading?
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I did a Rebuild Solution before posting. This is a web application and the only files I see in the bin folder are the dll files I am referencing. I'm not sure what else I should clean up.
I've seen so many posts on this but I just don't understand how to fix it.
HTML
Me.txtDeletedItem.Text = objDeleteLog.Name
[b]Me.txtDeleteReason.Text = objDeleteLog.Code.Description[/b]
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vb
Imports System.Windows.Forms.HtmlDocument
Public Class test_vbdotnet
Private Sub runtime()
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I want VB.NET to get access to the innerText and make a if statement out of it. But it always returns error. (see the comments for details.)
