Combo Box Selected Item Is Null - Assign An Empty String To It Instead?
Dec 9, 2011
I have a property called ReplacementTo and I set a value to it based on the selecteditem from the combobox, like this:
classEquipmentItem.ReplacementTo = cmbReplcmnt.SelectedItem.ToString
Now I can't use cmbReplcmnt.Text because what I actually need is the value of that SelectedItem
So problem is, if the user leaves the combobox as blank, it throws a null exception.I decided to use the IIf function then:classEquipmentItem.ReplacementTo = IIf(IsNothing(cmbReplcmnt.SelectedItem.ToString), classEquipmentItem.ReplacementTo = "", cmbReplcmnt.SelectedItem.ToString)
Unfortunately I still get the error I tried using a Try-Catch for it and it worked, but I don't want to rely on the Try-Catch, so I was wondering is there a another way to work this through?
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Dec 20, 2010
assign a particular value to each item in a combo box? Or, alternatively, some similar control? Specifically, I want a drop down list to select from a list of countries. I then want to get the ISO 2 letter abbreviation for the selected country. I could have a section of code like this
selected_country = cmb_country.SelectedItem.ToString()
if selected_country = "Afghanistan" Then
country_code = "AF"
ELSE IF selected_country = "Aland Islands" Then
[code]....
but this will get rather tedious.Is there an easier way to do it? I would like to be able to assign a value to each line in the list, like
Afghanistan, AF
Aland Islands, AX
Albania, AL
then get the value for the selected item. Is this possible? If not with a combo box, then any other control?
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Jun 28, 2010
This must've have been asked before but I couldn't locate it. In a mixed code project (VB and C#) we were debugging some old Visual Basic code where a statement as follows could be found:
If Request.Params("xxx") <> "" Then
'do something
I considered this a bug as Request.Params could be null, in which case the statement would've become false which wasn't the idea. So I thought. I just found out, -- probably for the tenth time and I will keep forgetting -- that the following two statements are not equal, while Nothing in VB should be equal to null in C# (thought I):
if(String.Empty == null) // always false
If String.Empty = Nothing Then ' always true
Should I dismiss this as a typical Microsoft backward compatibility effort, or should I consider this a huge error in the VB.NET compiler? Does anybody know the Microsoftean opinion on this oddity?
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May 27, 2011
how do i program by saying if a certain item is selected in a combo box then that item will not appear in a second combo box. i have this code for now but it does not work
[Code]...
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Jan 5, 2011
In my EF4 EntityModel I have an entity named Users. Users have the common UserName and Password string fields. If I do something like this
Dim u as new USERS
U.UserName = String.Empty
Then U.UserName are still Nothing.
But if I Do Something like this
Dim u as new USERS
u.UserName = "A"
u.UserName = String.Empty
Then U.UserName take String.Empty as value without problem.
The reason is the way that EF4 generate the UserName Property
Public Property UserName() As Global.System.String
Get
Return _UserName
End Get
[Code] .....
I do not want to make two assignations every time I want to set string.empty to a property with a nothing value, and I do not want to remember that I must do it in this way everytime, because I'm pretty sure that I will forget it and then I will introduce bugs in the code. I just want to assign the empty.string value to a property and the property take "" as value.
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May 27, 2011
how do i program by saying if a certain item is selected in a combo box then that item will not appear in a second combo box i have this code for now but it does not work
j = 0
Do While j < cmbSession.Items.Count
If (j <> lesson) Then
[code].....
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Mar 11, 2010
i need to use the selected item in combo box when user selects for example GREEN from be drop down list after than i need to put that green into the rest of my code, i need to draw a line in green but i dont know how to tell the program to use Green i tried setting up a variable for that, like : Dim rang as string = cmbcolor.selecteditem but it doesn't work
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May 9, 2011
I ahve a combox (cbnames) on a login form which is populated with items. I make a selection and click on ok. Form1 appears and I have a textbox which I want to fill with the selected item from the combo box.
However, on form1 (view code) I don't appear to see cbnames. cbnames is available on the login form. How do i make a combobox public? or accessible to other forms?
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Apr 1, 2011
I am having difficulty using the selected value of the combobox while calling it from the ok button click event procedure. While debugging in the Ok button coding none of the values are their, but for the comboxbox coding it appears that it is working properly.I made a seperate funciton to handle the combobox, could this be my error?
ComboBox
Public Function choosepipecomboboxcoding(ByVal cboChoosePipe As Object,
ByVal HDPE As Double,
ByVal PVC As Double,
[code].....
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Apr 26, 2009
Visual Basic Express Edition 2008 Problem. I have a Combo Box containing Country Names "New York" & "New Zealand", when "New York" is selected it shows the time and date of New York in label1 on the form and the time is updated every second by the timer, but when I make another selection by selecting New Zealand in the combox dropdown list then New York's time updation is stopped in label 1 and only New Zealand's time is updated in label 2. Why the timer control stops functioning for the first selection after we make a second selection in the combo box. I want that time for both label 1 country as well as label 2 country updates simultaneously on the form. My code is as follows:I have added 2 label controls and one combo box control on the form and following code.[code]Can any one advice me how all countries selected in the combo box one after other are dispplayed with updated time every second?
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Feb 10, 2012
I have a combobox that drops up instead of down. I'm setting the selected item to the one on top of the list. I'd like to move my mouse pointer to point to it, so that the user that wants to click on that item doesn't have to move his mouse. I found how to move the pointer, it is with this command:
Windows.Forms.Cursor.Position = New System.Drawing.Point(x,y)
but I need to know how to get the location of the selected item in the combobox.
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Jul 28, 2009
I'm using FileHelper to generate object's property. Here is an example of one property:
<FieldOptional(), _
FieldTrim(TrimMode.Both)> _
<FieldNullValue(GetType(String), " ")> _
Public StoreNo As String
As you can see the StoreNo will either have a value or " ", one of the business policy is to check if the StoreNo is empty or nothing if the object's StoreNo is empty or null then the record will not create.
I though about creating an HasValue Function in the class to check the StoreNo and other properties in the object but I feel like it is a hack.
Public Function HasValue() As Boolean
Dim _HasValue As Boolean = True
If StringHelper.IsNullOrBlank(Me.StoreNo) Then
[Code]....
I don't think this approach is an ideal solution. what if the StoreNo is remove or change to something else. What's the best approach to check object's property?
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Jan 4, 2012
I have a couple of textfields in a Windows form. One of these textfields is allowed to be NULL. When I enter a value for every field, it is all inserted, no problem. When I leave the field (txtGewicht) blank, I can't seem to be able to insert NULL in Access Database.
If Double.TryParse(txtGewicht.Text, 0) Then
klant.Gewicht = Double.Parse(txtGewicht.Text)
Else
[Code]....
This is what I get:
"Cannot set column 'Gewicht' to NULL, please use DBNull instead"
So I changed 'Nothing' to DBNull.value, but it then tells me that System.DBNull cannot be converted to type Double.
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Feb 7, 2011
I need to sort a DataTable or DataGridView by a column that is a string value, but with null/empty values at the BOTTOM when sorting ASCENDING. The DataTable is NOT populated by a SQL statement, so no order by. If I do
[Code]...
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Mar 5, 2009
I need to sort a DataTable or DataGridView by a column that is a string value, but with null/empty values at the BOTTOM when sorting ASCENDING.The DataTable is NOT populated by a SQL statement, so no order by.If I doDataGridView1.Sort(New RowComparer(System.ComponentModel.ListSortDirection.Ascending))then it throws an exception, saying that the DataGridView is DataBound, which is correct, but doesn't help me, and I want to keep it databound.
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May 1, 2012
I am creating a program that allows a user to view a list of foods in a combo box, add that food unto a list box, and adds all of the calories of that food together. When the user highlights their select food, the program automatically shows the amount of calories for that particular food in a text box. The program is getting the food and calorie information from an access database. I managed to get all of the food calories to add up properly, however, I ran into a problem. Sometimes, well, most of the time, when I select certain foods from the combo box, the program automatically reselects another random food, usually a food that begins with either an A, B, or C. Also, the other random food that the program chooses usually has the same amount of calories as the food I originally wanted to choose. I have over 6,000 items in the database. I don't understand why this is happening. This is what my code looks like for the button that adds each food to the list box:
Private Sub Button4_Click(sender As System.Object, e As System.EventArgs) Handles Button4.Click
Foods_Selected.Items.Add(ComboBox1.Text)
Static i As Single
[CODE]...
And this is what my code looks like for the button that adds all of the foods together:
Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
Dim x As Single
Dim TotalCalories As Single
[CODE]...
I have no idea what to try. It's like the program just skips over random foods, even though all of the information for them is in the database.
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Apr 20, 2010
How do you manipulate a string that you have selected from a Combo Box that has been upated dynamically from an MS Access Database table?I have strings that are "1, Surname, Forename" and need to get both the number, and the surname out to put back into a different database table.
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Nov 16, 2011
I am getting an error when i try to populate some combo boxes with a value, the combo box has values in and the right amount the code is getting the right number.
the error msg is "Object reference not set to an instance of an object."
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Aug 25, 2009
How do I assign a My.Settings.Item connection string to cmd.Connection connection string value?
Dim cmd As New SqlCommand()
cmd.Connection = My.Settings.Item("csStaffHoursWorked")
cmd.CommandType = CommandType.StoredProcedure
cmd.CommandText = "spSaveDeltekImport"
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Jul 5, 2010
In my application I have a listbox and SelectionMode should be MultiSimple because users need to see which items they selected. In another tab we have another listbox this one should show all the selection users had done in first tab. Private Sub
[Code]....
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Dec 21, 2010
I tried DbNull.Value but no luck. How do I assign a default value as null to a string parameter that is null in VB.NET? Its litte strange to see that VB does not have anything like plain null as most of the other languages do. Also what is the difference between null and DbNull and Nothing.
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Mar 5, 2010
I am not sure why VB makes everything such a pain. I have a fields which stores the date and time in the format required to store in MySQL database
[Code]...
Now I need to assign the AppDate to NUll like DBNull, but I am not able to do it directly. If I change AppDate to Date then I am not getting the required format.
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Aug 11, 2010
I have a array of strings and I am looping through them, but the string might be empty so I am trying this:
[Code]...
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Jun 7, 2011
Attempting to convert a possible null value into date/time field. Any easy way ?
[Code]...
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Mar 3, 2009
Anyway for my vb class we need to write an auto inquiry system. Im a total n00b and am struggling altogether. My interface is below Basically what my problem is (among others) is that I don't know how to assign prices to each model from the combo box. This is what I used to populate the two boxes:
[Code]...
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Jun 23, 2009
i have a date control on form (vb.net) and by default its value is current date. i want to make its value to null or empty so that no date is shown and user choose from the drop down date calendar.
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May 7, 2010
I am getting the attached error when any cell in a row is empty. How to avoid this error and to accept the null values?
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Apr 19, 2012
If you assign a value to a nullable integer via a ternary operator, it can't become null..While this question may seem like a duplicate of many, it is actually being asked for a specific reason.Take this code, for example: Dim n As Integer? = If(True, Nothing, 1) In that code, the ternary expression should be returning Nothing, but it's setting n to 0. If this were C#, I could say default(int?) and it would work perfectly. Now it looks like I am going to have to ditch the ternary and use a regular If block, but I really want to use the ternary. If Nothing were truly VB.NET's equivalent to C#'s default, how can you explain this behavior?
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Apr 24, 2011
when i try to assign data to an array from a text box, i get a null reference exception, stating "Object reference not set to an instance of an object".
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Jun 17, 2009
I am getting product id value some times null and empty from databasehere how i check if valule null and empty
productid = IIf(IsDBNull(TempDT.Rows(0).Item("productid")) =
True,
"", TempDT.Rows(0).Item("productid"))
[code].....
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