So I am trying to add items to a comboBox like this (the comboBox itself looks fine; it appears on screen and everything):
people_comboBox.Items.Add("Present");
people_comboBox.Items.Add("Late");
people_comboBox.Items.Add("Absent");
It only comes up with one item, which is "System.String[]".
What am I doing wrong?
Try creating List or Array of strings with those values and then set .DataSource property of ComboBox to this collection.
Related
I'm new to C# but not to programming. I've been toying around with VS, becoming more comfortable with the language and got stuck on a combobox bound to an int datatable column of an in-memory dataset.
I worked on a DataGridView and had no problems creating a DataGridViewComboBoxColumn and populating its dropdown list using a custom class comprised of Key:int and Desc:string. ValueMember = Key, DisplayMember = Desc. DataSource is left as null since the list is directly built into the ComboBox. Pick from the combobox and save changes works fine in the grid.
Then I moved to a ComboBox. Both the grid and the ComboBox have the exact same BindingSource. So yes they point to the same row at the same time.
I bind the ComboBox with:
cbCtrl.DataBindings.Add( "Text", myBindingSource, ColDBName );
Without populating the dropdown items of the ComboBox, I see the raw int value show up in the ComboBox. I change rows using the grid and the ComboBox value changes too. So it's good.
Then I populate the dropdown list of items in the ComboBox (the same as the grid's column tied to the same column) and it's trouble. The raw int value (eg 19) does not get matched to the proper "Key" item in the dropdown list of the ComboBox. I've tried DropDownStyle = DropDown & DropDownList but no luck with either. And I've looked for hours trying to find a fix. There are no events hooked up to the ComboBox. I expected automatic hookup of the raw value to the matching "Key" item in the ComboBox's dropdown list.
Is there something else to hook up? Frustrating since I expect something minor.
Any help would be Greatly appreciated. Thank you.
*Edit: The dropdown list actually comes from a populated BindingList<> and the BindingList<> is supplied as the ComboBox.DataSource.
I finally stumbled upon the answer:
cbCtrl.DataBindings.Add( "SelectedValue", myBindingSource, ColDBName );
That's all I needed. I got it from a great article
http://www.codeproject.com/Articles/24656/A-Detailed-Data-Binding-Tutorial?msg=5325959#xx5325959xx
I'm coding a combobox in C# and for some reason the items in the drop down don't have text. When I have selected an item, it is shown in the combo box text field (the drop down list is always blank whenever I click the drop down button). The datasource seems bound properly because the proper values are being returned when I select items, and the size of the drop down list will change depending on how many items the datasource has. Everything looks fine except for the fact that it seems like my drop down is populated with a bunch of empty strings, which it clearly isn't since as soon as an item is selected the proper text will display.
This is the relevant code:
if (list.Count > 0)
{
cboCustomers.DisplayMember = "Name";
cboCustomers.DataSource = list;
cboCustomers.ValueMember = "ID";
cboCustomers.SelectedIndex = 0;
}
I have looked for an answer to this but can't find it anywhere...I'm sure it's something really simple, but I can't figure it out. The closest problem I found had an answer suggested to set the display member before the data source, which clearly didn't work.
The list is populated from a database query. This will run on keyUp, the idea is that the list is populated as the person is typing based on the info given. So if I wrote 'S' I'd get a combobox with a dropdown that had all the clients starting with 'S'.
Given you don't have any anomalies in your binding, you are probably being affected by DrawMode property of your ComboBox, which may be set to OwnerDrawFixed or OwnerDrawVariable. Set it to Normal and things should get better.
as soon as an item is selected the proper text will display.
A foreground color the same as the background color will produce the same results you are seeing.
In WPF, I select multiple items in the listview. In the code-behind, I inserted an element at index 2 using ObservableCollection.SetItem(). The multiple items I selected a while ago will be deselected. How can I insert an element in the listview while not losing the multiple items I selected?
The code below triggers the deselection of the selected items.
this.SetItem(index2, new student("name",age,"school"));
Any help is appreciated. Thanks
For one, SetItem() does not insert an item, it replaces it. To insert an item use Insert().
As for multi-selection, you're best off implementing a bind-able multi-select ListView. One issue with ListView is that the SelectedItems is not a DependencyProperty so it cannot be bound to, and isn't the most reliable thing to deal with in ViewModels or code.
A good example of how to implement a better ListView can be found Here. There is a 3-part series on binding ListViews there which can provide some useful ideas as well.
Create a list of bools for each item in your checklist.
Before inserting new item, check each existing item and see if it is selected and store result in bool list.
Once item is inserted, simply parse back over the bool list and re-set the previously selected items.
I have a ComboBox whose items I have populated from a database. I wish to know if the selected item has changed from when I initially displayed the ComboBox. How can I determine this?
it is not simple- try to handle EndEdit event/ But you couldnot handle select change in dropdown list
You could try storing the default value in the .Tag property and comparing the two whenever you need.
After binding a list to combobox, its dataSource.Count is 5 but, combobox item count is 0.
how can it be?
I'm used to Web programming and this is in Windows Forms.
So no combo.DataBind(); method exists.
The problem here is, I'm trying to set the selected item programmatically. Since I don't see the combo.Items collection filled, I cannot set the desired item.
Update
A total update is needed I guess:
datasource contains 7 items
when bound to combobox, DisplayMember and ValueMember are appropriately implemented
after databound, through the gui, I can clearly see the 7 items in the combobox
combobox.DataSource.Count = 7 and combobox.Items.Count = 0
So the problem is here; since after databound no items are there in the ItemCollection of combobox; I cannot search for one to match and set the appropriate one.
Here is a image for better understanding (But I'm pretty sure I'm missing sth simple)
After adding ddl.BindingContext = new BindingContext(); before the BindingSource assignment, everything worked fine.
If you'd expand DataSource items in debuger, you'd probably notice that 1st element on list is null. That is why DataSource does not render ComboBox Items. Removing null items from the list should do all the work;
I had the same problem, but in my case it was caused by calling
combobox.Sorted = True
in InitializeComponent. I guess that call initializes Items, which then prevents the assignment to DataSource from updating it (Items).