Select Values from two combobox from a list of combobox? - asp.net

Question

I have six combobox placed on my form and at same time i want user can select values from maximum of two combobox.
for this i have take a counter variable which get incremented every time when selectedindex of a combobox get changed but didn't reach to solution.
Can you guys explain how can i do this ?

Answer 1

I created an example for you. I hope it can be usefull.
ASP.Net Page:
<form id="form1" runat="server">
<div>
<div>
<label>Combobox 1</label>
<asp:DropDownList runat="server" OnSelectedIndexChanged="Unnamed1_SelectedIndexChanged" AutoPostBack="True">
<asp:ListItem>Select</asp:ListItem>
<asp:ListItem>Combo-1-1</asp:ListItem>
<asp:ListItem>Combo-1-2</asp:ListItem>
</asp:DropDownList>
</div>
<div>
<label>Combobox 2</label>
<asp:DropDownList runat="server" OnSelectedIndexChanged="Unnamed1_SelectedIndexChanged" AutoPostBack="True">
<asp:ListItem>Select</asp:ListItem>
<asp:ListItem>Combo-2-1</asp:ListItem>
<asp:ListItem>Combo-2-2</asp:ListItem>
</asp:DropDownList>
</div>
<div>
<label>Combobox 3</label>
<asp:DropDownList runat="server" OnSelectedIndexChanged="Unnamed1_SelectedIndexChanged" AutoPostBack="True">
<asp:ListItem>Select</asp:ListItem>
<asp:ListItem>Combo-3-1</asp:ListItem>
<asp:ListItem>Combo-3-2</asp:ListItem>
</asp:DropDownList>
</div>
<div>
<label>Combobox 4</label>
<asp:DropDownList runat="server" OnSelectedIndexChanged="Unnamed1_SelectedIndexChanged" AutoPostBack="True">
<asp:ListItem>Select</asp:ListItem>
<asp:ListItem>Combo-4-1</asp:ListItem>
<asp:ListItem>Combo-4-2</asp:ListItem>
</asp:DropDownList>
</div>
<div>
<label>Combobox 5</label>
<asp:DropDownList runat="server" OnSelectedIndexChanged="Unnamed1_SelectedIndexChanged" AutoPostBack="True">
<asp:ListItem>Select</asp:ListItem>
<asp:ListItem>Combo-5-1</asp:ListItem>
<asp:ListItem>Combo-5-2</asp:ListItem>
</asp:DropDownList>
</div>
<div>
<label>Combobox 6</label>
<asp:DropDownList runat="server" OnSelectedIndexChanged="Unnamed1_SelectedIndexChanged" AutoPostBack="True" Height="19px">
<asp:ListItem>Select</asp:ListItem>
<asp:ListItem>Combo-6-1</asp:ListItem>
<asp:ListItem>Combo-6-2</asp:ListItem>
</asp:DropDownList>
</div>
<div>
<asp:Label ID="Label1" runat="server" Text=""></asp:Label>
</div>
</div>
</form>
ASP.Net Code-Behind
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
ViewState["DropdownSelectLimit"] = 0;
}
}
protected void Unnamed1_SelectedIndexChanged(object sender, EventArgs e)
{
if (ViewState["DropdownSelectLimit"] != null)
{
if ((int)ViewState["DropdownSelectLimit"] < 2)
{
int count = (int)ViewState["DropdownSelectLimit"];
count++;
ViewState["DropdownSelectLimit"] = count;
}
else
{
DropDownList dropDown = (DropDownList)sender;
dropDown.SelectedIndex = 0;
Label1.Text = "You can't select any option anymore";
}
}
}
If you have any question just ask me on comments :)

Answer 2

I created a setup for Winforms as it wasn't complete clear if you wanted it for Winforms or ASP.Net
I will not handle how you should fill a combobox, i'm sure you know how to do this, whether this is filled static or dynamic.
My solution (although quite rude) makes you link a simplified handler named HandleComboBoxSelectedIndexChanged to each combobox SelectionChanged event. This can be The SelectedItemChanged, SelectedValueChanged or SelectedIndexChanged.
Quite important: each combo needs a null value.
//will hold a list of your combobox names
private List<string> SelectedCombos;
//form load: Link the events to the correct handler
private void Form_Load()
{
foreach(var combo in Controls)
{
if(combo is ComboBox)
combo.SelectedValueChanged += HandleComboBoxSelectedIndexChanged;
}
}
//will handle the selectedIndexOrItemchanged event
private void HandleComboBoxSelectedIndexChanged(object sender, EventArgs e)
{
if(SelectedCombos = null)
SelectedCombos = new List<string>();
var combo = (ComboBox)sender;
if(combo.SelectedValue == null)
if(!SelectedCombos.Exist(combo.Name))
SelectedCombos.Remove(combo.Name);
else
if(!SelectedCombos.Exist(combo.Name) && SelectedCombos.Count < 2)
SelectedCombos.Add(combo.Name)
SetComboAvailability();
}
Another function which might be useful, whenever 2 combos are selected, make the enabled state false. This means that your user can only select from the 2 selected combos untill one of them is reset at it's null position. This way your user can only select what is possible.
//set the combos availability, less then 2 selections ok, own selection also ok else not ok
private void SetComboAvailability()
{
foreach(var combo in Controls)
{
if(combo is ComboBox)
combo.Enabled = SelectedCombos.Count < 2 || SelectedCombos.Contains(combo.Name);
}
}
Below a small example of how you could retrieve all your values from the combos based on their names.
//Something for handling all the values
private void RetrieveValues()
{
foreach(var v in SelectedCombos)
{
var combo = this.Controls.Find(v);
if(combo is ComboBox)
{
//do something with the selectedValue
var val = combo.SelectedValue; // or selecteditem
MessageBox.Show(string.Format("Control {0} has value {1}", combo.Name, val);
}
}
}
If you don't understand something feel free to ask.
Also:
the EventArgs property might change according to the selected event:
do: _comboBox1.SelectedValueChanged+= (TAB TWICE in VS) to see what the automatic code generation looks like. (always handy)
Example:
_comboBox1.SelectedValueChanged += _comboBox1_SelectedValueChanged;
private void _comboBox1_SelectedValueChanged(object sender, EventArgs e){}