Develop Reference

c# confirm each combobox has a unique value selected

I have a winform with a group of comboboxes, all of the comboboxes with the same list items in them.
I need a way to confirm that when the user is done selecting a value in each box that they only selected each list value once.
Ex:
cbox1 cbox2 cbox 3
Item A Item B Item A (this needs to flag an error since Item A is already selected in cbox1)
I was thinking trying to use the selectedvaluecommited action (as after i populate the list I change the selected index to -1 so they all show "empty" to start) but the loop to make it work seems to be eluding me.
background: this is choosing fields to build a spreadsheet and the user needs to choose the field order.

You can do it like this (quick and dirty):
Add SelectedIndexChanged handler for all three comboboxes (in Form_Load in example)
comboBox1.SelectedIndexChanged += CheckComboBoxes;
comboBox2.SelectedIndexChanged += CheckComboBoxes;
comboBox3.SelectedIndexChanged += CheckComboBoxes;
in CheckComboBoxes method do your checking:
private void CheckComboBoxes(object sender, EventArgs e)
{
if (comboBox1.SelectedIndex == comboBox2.SelectedIndex ||
comboBox1.SelectedIndex == comboBox3.SelectedIndex ||
comboBox2.SelectedIndex == comboBox3.SelectedIndex)
MessageBox.Show("comboboxes are not unique");
}
EDIT:
this is approach when having n comboboxes. Put all items into list, select distinct values and compare that distinct count with items count... Something like this:
private void CheckComboBoxes(object sender, EventArgs e)
{
List<string> comboValues = new List<string>();
foreach (Control c in this.Controls)
{
if (c is ComboBox && !string.IsNullOrEmpty((c as ComboBox).SelectedItem.ToString()))
comboValues.Add((c as ComboBox).SelectedItem.ToString());
}
if (comboValues.Distinct().ToList().Count < comboValues.Count)
MessageBox.Show("not all combos are unique");
}

Here's an approach you can take.
To make the affected comboboxes easy to distinguish, put them all in a GroupBox container.
Write a validation method for your group box.
Subscribe to the group box Validating event by attaching it to your validation method.
In your validation method, loop through all the ComboBox controls in the group box and check if there are any duplicates, and issue an error if so.
For example, assuming the group box is called groupBox1:
private void GroupBox1_Validating(object sender, CancelEventArgs e)
{
base.OnValidating(e);
var selectedIndices = groupBox1.Controls.OfType<ComboBox>().Select(item => item.SelectedIndex);
var anyDuplicates = selectedIndices.GroupBy(x => x).Any(x => x.Count() > 1);
if (!anyDuplicates)
return;
MessageBox.Show("There are duplicates!");
e.Cancel = true;
}
And subscribe to the group box Validating event in the Form1 constructor:
public Form1()
{
InitializeComponent();
groupBox1.Validating += GroupBox1_Validating;
}
Sometimes when validating like this, you need to prevent the validation logic from executing if the user clicks the Cancel button. You're supposed to be able to set the CausesValidation property of the Cancel button to false to prevent this, but I find that it doesn't work for me.
Instead, I just use a bool cancelling field which I set to true in the Cancel button handler:
private void cancelButton_Click(object sender, EventArgs e)
{
cancelling = true;
this.Close();
}
bool cancelling;
And then add the following to the start of GroupBox1_Validating():
if (cancelling)
return;

If it is possible to have different UI design then my suggestion goes as under:
Alternative UI Design - A
Create One ListBox ListFieldsOriginal and populate
Create Second ListBox ListUserSelection, keep it empty initially
Provide buttons as under:
Button '>' means add currently selected item from ListFieldsOrginial to ListUserSelection at end; and remove that item from ListFieldsOriginal
Button '<' means remove currenly selected item from lstUserSelection; and add that item back to ListFieldsOriginal (of course at end)
NOTE: If adding item back to ListFieldsOriginal is your requirement then extra coding is required to find its appropriate index in the ListFieldsOriginal.
Alternative UI Design - B
Create One CheckedListBox ListFieldsOriginal and populate
Create one ListBox ListUserSelection, keep it empty initially
Define ItemCheck event handler for ListFieldsOriginal to add/remove items to/from ListUserSelected.
if (e.CurrentValue==CheckState.Unchecked)
{
string item = ListFieldsOriginal.Items[item];
ListUserSelection.Items.Add(item);
}
else
{
string item = ListFieldsOriginal.Items[item];
ListUserSelection.Items.Remove(item);
}

How call the Text_Changed Event for multiple text box controls on a form in C# winforms

I have form that has about 20 TextBox controls and I would like to fire the Text_Changed event with out adding the event for each individual text box. Is there a way to loop through the text boxes to fire this event? What I am trying to do is clear a label control when the text changes. Instead of displaying a message box, for error descriptions, I use a label control to display the message. I also set it up where if a text box has invalid data, I select all text and give focus to that TextBox so when user re-enters information the label control clears the message.
Edit:
To clear up some confusion, here is some of my code from my validation method
if (txtBentLeadsQty.Text == "")
{
//ValidData = true;
BentLeadsCount = 0;
}
else
{
if (int.TryParse(txtBentLeadsQty.Text.Trim(), out BentLeadsCount))
ValidData = true;
else
{
ValidData = false;
lblError.Text = "Bent Lead Qty must be a numeric value";
txtBentLeadsQty.SelectAll();
txtBentLeadsQty.Focus();
}
}
I already have a way to check for numeric values, and I put code in to select all text entered and gave focus if the values are not numeric, I just want to have a way to clear the Label control when the the text is changes like if the user hit backspace or starts typing that why if the error occurs, I highlight all the text in that TextBox if it is not valid. I can do this if I put code in every text boxes TextChanged event, but to save coding I was wondering if there is way to clear the label control if any of the text boxes throws an error from my validation method instead of adding individual events for 20 text boxes.
Note: Not all text boxes will have data entered, these are quantity text boxes I put code in to assign a 0 to the variable if the TextBox in null.

You can use the following code:
private void Form1_Load(object sender, EventArgs e)
{
foreach (Control ctrl in this.Controls)
{
if ((ctrl as TextBox) != null)
{
(ctrl as TextBox).TextChanged += Form1_TextChanged;
}
}
}
private void Form1_TextChanged(object sender, EventArgs e)
{
MessageBox.Show((sender as TextBox).Name);
}

I'm assuming you want to add the same handler to all textboxes in the form dynamically, i.e. without having to add them for each text box in the visual editor (or code).
If so, this might be what you need:
// Iterate over all controls in the current form:
foreach (var ctl in Controls)
{
// Check if the current control is a textbox
// (will be null if it is of another type)
var txtBox = ctl as TextBox;
if (txtBox != null)
{
txtBox.TextChanged += YourMethod();
}
}

Sounds like you want to programmatically fire the method on each text box.
First, create an array of around 20 text boxes.
var textBoxes = new []{textBox0, textBox1, textBox2};
Loop through the each box and call the text changed method
foreach(var textBox in textBoxes)
{
TextChangedMethod(textBox);
}
If the method you are calling was generated by Visual Studio, it will take a second parameter for EventArgs. You can simply pass a null value for that.
TextChangedMethod(textBox, null);

Create a method, something like this:
public void TextChanged(object sender, EventArgs e)
{
//Text-changed code here.
}
At this point you can click on each text box on your form and add your new method to the event you want to occur. Click a text box on your form, and click the thunderbolt icon in the properties menu and scroll down to "TextChanged" event. Change that drop down on that event to your new method.
OR
Add the event at run time after you initialize the forms components:
textBox1.TextChanged += new EventHandler(TextChanged);
textBox2.TextChanged += new EventHandler(TextChanged);
textBox3.TextChanged += new EventHandler(TextChanged);
This could be done easier if you add all the text boxes to an array, and loop through them with a foreach to add the event to each one. You could also just grab all the text boxes from the form and loop the same way, though I don't know if you have other controls/text boxes that would make you avoid this method.

Use a foreach statement.
Example
List<TextBox> TextblockCollection = null;//You have to add them all individually to the list
foreach (var text in TextblockCollection)
{
//Change the text to the same thing, firing the method
text.Text = text.Text
}

So you want to check when any of the text boxes are changed, then check if the new input in the changed textbox is a number (I'm assuming an integer) and then display a message in a label if it's not a number.
public MainForm()
{
InitializeComponent();
foreach (Control control in this.Controls)
{
if (typeof(control)==typeof(TextBox))
{
(control as TextBox).TextChanged += CommonHandler_TextChanged;
}
}
}
private void CommonHandler_TextChanged(object sender, EventArgs e)
{
int number;
string input=(sender as TextBox).Text;
bool isnumber=false;
isnumber = Int32.TryParse(input, number);
if(isnumber==false)
{
yourLabel.Text = "This textbox contains an incorrect number: "
+(sender as TextBox).Name;
}
else{ /*use the number*/ }
}

c# format textboxes to currency when they lose focus

I have several lists of text boxes on a form each representing a column of a database. I want to update the form each time the user exits one of the boxes for price. the name of this list is priceBox[]. I am aware of the lostFocus event but I cant seem to figure a way to get it to work for a collection and this list can grow so I cant have a fixed number. I dont have any code for this yet. if it helps the text box controls are contained in a panel named panel1.
I have tried searching and cant find anything on this. only for singular instances, like updating 1 text box.
sorry if this is a duplicate but I did try to search. also I am new to c#.
thanks.

One approach is adding a ControlAdded handler to the panel, so every time a new textbox is added, it automatically adds LostFocus handler for it. Step-by-step below:
For your panel you bind a handler ControlAdded event, which would be something like:
private void Panel1_ControlAdded(object sender, ControlEventArgs e)
{
var tb = e.Control as TextBox;
if (tb != null)
{
tb.LostFocus += new EventHandler(TextBox_LostFocus);
}
}
Then in TextBox_LostFocus you can add whatever logic you want
void TextBox_LostFocus(object sender, EventArgs e)
{
var tb = sender as TextBox;
if (tb != null)
{
// modify tb.Text here, possibly like this...
tb.Text = String.Format("{0:C}", Decimal.Parse(tb.Text));
}
}
To update all existing controls (not tested)
foreach (TextBox in panel1.Controls)
{
tb.LostFocus += new EventHandler(TextBox_LostFocus);
}

detect keypress event for all textboxes inside a nested TableLayoutPanel

I have a series of nested TableLayoutPanelcontrols which each of them contains lots of TextBox controls.
I think it is insane to make a keypress event for each of the textboxes, So what I am trying to do is to have a common event method and then apply the event for all textboxes on FormLoad event. What I want to do is to see if the user has pressed Enter key in any of those textboxes.
This is my common method (I hope nothing is wrong with it!):
private void ApplyFiltersOnEnterKey(object sender, KeyPressEventArgs e)
{
if (e.KeyChar == (char)13)
{
tsApplyFilters_Click(this, null);
}
}
And I have the following code in Load event of my form:
//Applying common event for all textboxes in filter options!
foreach (var control in tableCriterias.Controls)
{
var textBox = control as TextBox;
if (textBox != null)
textBox.KeyPress += new KeyPressEventHandler(this.ApplyFiltersOnEnterKey);
}
Well, maybe you can guess already, the codes above does not work! I can list the problems I can think of:
tableCriterias which is the parent TableLayoutPanel and all the other layout panels are inside it, is itself inside a series of Panel SplitContainer and....Do I need to point this in my loop?
Or do I recursively loop over each layoutpanel inside the main layoutpanel?
Or the whole idea is wrong?!!?
Thanks.

private void Recursive(TableLayoutPanel tableCriterias)
{
foreach (var control in tableCriterias.Controls)
{
var textBox = control as TextBox;
if (textBox != null)
textBox.KeyPress += new KeyPressEventHandler(this.ApplyFiltersOnEnterKey);
else if(control is TableLayoutPanel)
Recursive(control as TableLayoutPanel);
}
}
And call this method for parent TableLayoutPanel

How to attach different EventHandlers to combos of a single DataGridView

I am using VS2005 (c#.net desktop application). When I add an eventHandler to a combo of datagridview, it's automatically adding the same eventhandler to all other combos of the same datagridview.
My code:
private void dgvtstestdetail_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
{
DataGridView grid = (sender as DataGridView);
if (grid.CurrentCell.OwningColumn == grid.Columns["gdvtstd_TestParameter"])
{
ComboBox cb = (e.Control as ComboBox);
cb.SelectedIndexChanged -= new EventHandler(dvgCombo_SelectedIndexChanged);
cb.SelectedIndexChanged += new EventHandler(dvgCombo_SelectedIndexChanged);
}
}
I want to add different event handlers to different combos in datagridview. Please tell me how can I do it.

By default, I believe that the DataGridColumn reuses the same instance of ComboBox for each cell. This is an optimization used by the grid to keep the number of created editing controls low.
The easiest thing is just to have one event handler, check the cell being edited, and take the appropriate action.
public void dvgCombo_SelectedIndexedChanged()
{
if (<condition1>)
ExecuteConditionOneLogic();
if (<condition2>)
ExecuteConditionTwoLogic();
}
A more advanced solution would be to create your on custom DataGridViewColumn implementation which does not share an editing control. I wouldn't recommend this unless you really have some reusable functionality.