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Text box does not update after changing after selected item in ComboBox (ComboBox gets the list from a text file)

I am confronting with an issue with the ComboBox in a WinForms app. The combo box contains a list with items that are grabbed from a TXT file. To read and update the list I added the following code to Form_Load.
string[] lineOfContents = File.ReadAllLines(Application.StartupPath + #"Items.txt");
foreach(var line in lineOfContents)
{
string[] tokens = line.Split(',');
ComboBox.Items.Add(tokens[0]);
}
All nice and good, the list does update. However, I also have some TextBoxes that are changing their text based on the string of the selected item in the ComboBox. For example, when the selected item in the ComboBox is "Example", the text in the first text box should change from empty to "I am an example!", but it doesn't and remains empty. The code for it is:
if(ComboBox.SelectedItem == "Example")
{
TextBox.Text = "I am an example!";
}
At first I though it's a conversion issue so I tried to use Convert.ToString(tokens[0]); but it did not work as well.
Any suggestions on what I should try next to fix this issue?

You are describing bound behavior so the first thing to check is whether the TextBox is properly connected to the event fired by the ComboBox. Something like this would be the first step to getting the behavior you describe.
public MainForm()
{
InitializeComponent();
// Subscribe to the event here OR using the Designer
comboBox1.SelectedIndexChanged += comboBox1_SelectedIndexChanged;
}
private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
if (comboBox1.Text == "Example")
{
textBox1.Text = "I am an example!";
}
else textBox1.Text = comboBox1.Text;
}
But the missing step in the code you posted is actually selecting a value in the combo box after the tokens are loaded into it. This leaves the text box blank as demonstrated here:
private void buttonLoad_Click(object sender, EventArgs e)
{
loadMockFile();
}
private void loadMockFile()
{
string[] lineOfContents = MockFile;
foreach (var line in lineOfContents)
{
var token =
line.Split(',')
.Select(_ => _.Trim())
.Distinct()
.First();
if (!comboBox1.Items.Contains(token))
{
comboBox1.Items.Add(token);
}
}
}
string[] MockFile = new string []
{
"Example, A, B,",
"Other, C, D,",
};
So the solution is to make sure that you make a selection after the tokens are loaded into the ComboBox, for example as shown in the handler for the [Load + Select] button:
private void buttonLoadPlusSelect_Click(object sender, EventArgs e)
{
loadMockFile();
var foundIndex = comboBox1.FindStringExact("Example");
comboBox1.SelectedIndex = foundIndex;
}

ListBox deletion

I have a listbox, with 2 buttons, new and delete. new adds an item into the list box, and the delete button should delete the item out of the list box. The list box items are tied to a class that stores user entered data from text boxes below.
private void AddListBox()
{
lstCondition.BeginUpdate();
Condition cond = new Condition("");
cond.Name = string.Format("Condition {0}", _selection.NetConditions.Count + 1);
_selection.NetConditions.Add(cond);
lstCondition.EndUpdate();
lstCondition.SelectedItem = cond;
cboNetCondition.Properties.Items.Clear();
cboNetCondition.Properties.Items.AddRange(NetCondition);
cboControlType.Properties.Items.Clear();
cboControlType.Properties.Items.AddRange(ControlType);
cboFlowRate.Properties.Items.Clear();
cboFlowRate.Properties.Items.AddRange(FlowRate);
}
private void btnNew_Click(object sender, EventArgs e)
{
AddListBox();
}
the cbo items are comboboxes, whose data gets tied in the condition class to each instance of the list box.
public frmNetConditions(Condition condo, Selection selection)
{
InitializeComponent();
_selection = selection;
lstCondition.DataSource = _selection.NetConditions;
condition = _selection.NetConditions.Count;
}
private void btnDelete_Click(object sender, EventArgs e)
{
selectedCondition = (Condition)lstCondition.SelectedItem;
cboControlType.SelectedIndex = -1;
cboNetCondition.SelectedIndex = -1;
cboFlowRate.SelectedIndex = -1;
txtFlowRate.Text = string.Empty;
txtStatPressure.Text = string.Empty;
txtDampOpening.Text = string.Empty;
txtDensity.Text = string.Empty;
cboDensity.SelectedIndex = -1;
lstCondition.Items.Remove(lstCondition.SelectedItem);
lstCondition.Refresh();
}
After pressing this delete button, the listbox, still contains the item i wish to delete, im unsure why thats the case?
Update with datasource
public List<Condition> NetConditions { get { return _netconditions; } }

As already suggested, you should bind to a BindingList<Condition> instead of a List<Condition>. This allows you to change the datasource and the control (ListBox) to get notified by your changes. The code should look like this:
lstCondition.ValueMember = "ConditionId";
lstCondition.DisplayMember = "Name";
lstCondition.DataSource = NetConditions;
After defining the binding, the correct way of operating on the ListBox items is to remove from the datasource, not the ListBox itself:
// SelectedItem should be checked for null (no selection is an option)
NetCondition.Remove((Condition)lstCondition.SelectedItem);
However, if you plan to change properties from an element (so, not the list itself), the control is notified only if your element (Condition) implements INotifyPropertyChanged interface.

Add dropdown for a specific cell in a datagridview

I am trying to add different controls to cells in the same column. The drop down does not show and there is no visible setter:
private void AddBooleanDropDown(DataGridView grid, int row, KeyValuePair<string, string> kvp)
{
DataGridViewComboBoxCell dropDownCell = new DataGridViewComboBoxCell();
dropDownCell.DataSource = new string[] { "True", "False" };
grid.Rows[row].Cells["Value"] = dropDownCell;
}

Not sure if this will be helpful to you, but maybe an alternative method?
I wanted to be able to update an excel spreadsheet that I read into a DataGridView and give the user a few options. I used a ContextMenuStrip that would display on a MouseClick event.
It displays a small menu when you right click on a cell:
If it's not what you're looking for at all, sorry; just perhaps an alternate solution:
////////////////////////////////////////////////////////////////////////
//Change Priority Strip
////////////////////////////////////////////////////////////////////////
ContextMenuStrip changePriority = new ContextMenuStrip();
ToolStripMenuItem highPriority = new ToolStripMenuItem("High Priority");
changePriority.Items.Add(highPriority);
highPriority.Click += new EventHandler(changePriorityHighEvent);
ToolStripMenuItem normalPriority = new ToolStripMenuItem("Normal Priority");
changePriority.Items.Add(normalPriority);
normalPriority.Click += new EventHandler(changePriorityNormalEvent);
ToolStripMenuItem lowPriority = new ToolStripMenuItem("Low Priority");
changePriority.Items.Add(lowPriority);
lowPriority.Click += new EventHandler(changePriorityLowEvent);
////////////////////////////////////////////////////////////////////////
private void gridView_CellMouseClick(object sender, DataGridViewCellMouseEventArgs e)
{
if (e.Button == MouseButtons.Right) //On Right Click
{
DataGridView.HitTestInfo hit = gridView.HitTest(e.X, e.Y); //Get the clicked cell
if (e.RowIndex < 0) //If it's a header, ignore
return;
gridView.CurrentCell = gridView[e.ColumnIndex, e.RowIndex]; //Select the cell for future info
if (gridView.CurrentCell.ColumnIndex == 6) //If this is the priority column
{
changePriority.Show(Cursor.Position.X, Cursor.Position.Y); //Show the strip
}
}
}
private void changePriorityHighEvent(Object sender, EventArgs e) {
//make changes
}
private void changePriorityNormalEvent(Object sender, EventArgs e) {
//make changes
}
private void changePriorityLowEvent(Object sender, EventArgs e) {
//make changes
}

Here is very good MSDN Example.
The DataGridView control provides several column types, enabling your users to enter and edit values in a variety of ways. If these column types do not meet your data-entry needs, however, you can create your own column types with cells that host controls of your choosing. To do this, you must define classes that derive from DataGridViewColumn and DataGridViewCell. You must also define a class that derives from Control and implements the IDataGridViewEditingControl interface.

Not sure if you can change a specific cell in a grid unless it's the same type.
You could try adding a new column of combo boxes all with that data source
var newCol = new DataGridViewComboBoxColumn()
{
DataSource = new string[] { "True", "False" }
};
grid.Columns.Add(newCol);
also you might want to check that the int your passing in isn't greater than the number of rows.

Update DataGrid's ItemsSource on SelectionChanged event of a ComboBox

I subscribed to a SelectionChangedEvent on a ComboBox in a DataGrid with the following code:
public static DataGridTemplateColumn CreateComboboxColumn(string colName, Binding textBinding, SelectionChangedEventHandler selChangedHandler = null)
{
var cboColumn = new DataGridTemplateColumn {Header = colName};
...
if (selChangedHandler != null)
cboFactory.AddHandler(Selector.SelectionChangedEvent, selChangedHandler);
...
return cboColumn;
}
The handler I actually register contains:
private void ComboBoxSelectionChangedHandler(object sender, SelectionChangedEventArgs e)
{
Console.WriteLine(#"selectHandler");
var cboBox = sender as ComboBox;
if (cboBox == null)
return;
if (cboBox.IsDropDownOpen) // a selection in combobox was made
{
CommitEdit();
}
else // trigger the combobox to show its list
cboBox.IsDropDownOpen = true;
}
... and is located in my custom DataGrid class.
If I select an item in the ComboBox, e.AddedItems and cboBox.SelectedItem contains the selected value, but nothing is changed on CommitEdit().
What I want is to force a commit to directly update the DataGrid's ItemsSource, when the user selects an item in the drop-down-list. Normally this is raised if the control looses focus...
The link in the solution found in this thread is not available any more and I don't know how to use this code.

I created a tricky, but working, solution for my problem. Here's the modified handler from above:
private void ComboBoxSelectionChangedHandler(object sender, SelectionChangedEventArgs e)
{
Console.WriteLine(#"selectHandler");
var cboBox = sender as ComboBox;
if (cboBox == null)
return;
if (cboBox.IsDropDownOpen) // a selection in combobox was made
{
cboBox.Text = cboBox.SelectedValue as string;
cboBox.MoveFocus(new TraversalRequest(FocusNavigationDirection.Right));
}
else // user wants to open the combobox
cboBox.IsDropDownOpen = true;
}
Because my ComboBoxColumn is a custom DataGridTemplateColumn I force it to show its list, when the user first selects the cell.
To change the bound items value I manually overwrite the displayed text with recently selected item and force the UI to select another item (in this case the control to the right) to make an implicit call to CellEditEnding event, which (in my case) commits the whole row:
private bool _isManualEditCommit = false;
private void _CellEditEnding(object sender, DataGridCellEditEndingEventArgs e)
{
// commit a manual edit
// this if-clause prevents double execution of the EditEnding event
if (!_isManualEditCommit)
{
Console.WriteLine(#"_CellEditEnding() manualeditcommit");
_isManualEditCommit = true;
CommitEdit(DataGridEditingUnit.Row, true);
_isManualEditCommit = false;
checkRow(e.Row);
}
}
Maybe I could help somebody with this "dirty" solution ;-)

Confusion in DataGridView combobox

I'm currently using DataGridView with three cells, and the first cell is
DataGridViewComboBoxColumn object, and I want to ensure whenever I select any new item in DataGridViewComboBoxColumn object other cells of dataGridview get empty. It doesn't matter if I reselect the same item again.
Could anyone please tell me how should I ensure that I've selected new item in DataGridViewComboBoxColumn object? Which property or method should I use for this approach?

You can declare a global List<int> gridComboSelections and when you bind your DataSource to your grid, you can fill this list with the SelectedValues of the comboboxes. When any of the combobox' value is changed, find the position of the combobox and check if it is same with gridComboSelections[i]. If it is same end operation, if not do what you want with it. If the value is changed, remember to change the corresponding value on your List.

You can refer following code which does same thing.
private void dataGridView1_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
{
ComboBox combo = e.Control as ComboBox;
if (combo != null)
{
combo.SelectionChangeCommitted += new EventHandler(combo_SelectionChangeCommitted);
}
}
void combo_SelectionChangeCommitted(object sender, EventArgs e)
{
DataGridViewComboBoxEditingControl combo = sender as DataGridViewComboBoxEditingControl;
if (combo != null)
{
for (int columnIndex = 0; columnIndex < dataGridView1.ColumnCount; columnIndex++)
{
if (columnIndex != combo.EditingControlDataGridView.CurrentCell.ColumnIndex)
{
dataGridView1[columnIndex, combo.EditingControlRowIndex].Value = null;
}
}
}
}