CODEWITHSUNDEEP
c#winformscombobox
Nagu
Nagu

Reputation: 5114

combobox default value winforms c#

Hi here i want to bind some values to check box dynamically.

dataset ds = //getting emp values form database;
cbemp.ValueMember = "empid";
cbemp.DisplayMember = "empname";
cbemp.DataSource = ds.Tables["emp"];

it is working fine. But i want to add

"Select emplyoee" as a default value of check box .

But my check box directly adding values like

a1
a2
a3

like this.

I tried like this

cbemp.Items.Insert(0, "Select emplyoee");

but it is not working

how can i add it?

Upvotes: 5

Views: 16351

Answers (7)

Wanny Miarelli
Wanny Miarelli

Reputation: 744

In my case ( databinded combobox ) i solved the problem like this. Of course the best way is the Kevin Coulombe one.

ComboBox.SelectedIndex = -1;
ComboBox.Text = "Please, select something";

With a bit of code you can manage this scenario pretty easy.

Upvotes: 0

Harry
Harry

Reputation: 1825

if ComboBoxStyle is set to DropDownList (so user cannot edit combobox) then the easiest way to make sure the user selects an item is to set selectedIndex=-1, you can always add "Please Select" etc ABOVE the combobox.

Upvotes: 0

Andrew Jens
Andrew Jens

Reputation: 1052

The above accepted solution is better, but one trick that might come in handy sometimes is to Union a "fake" record to the SQL that is returning the recordset for the data-binding. In this case, something like:

select 0 as empid, 'Please select' as empname
union
select empid, empname from emp
order by empid

Of course you will have to protect the database from accidentally writing the "0" record back (e.g. if the user doesn't make a selection), but that isn't too hard.

Upvotes: 0

Kevin Coulombe
Kevin Coulombe

Reputation: 1575

Inserting data in your data source is a bad idea. It promotes breaking your layers' abstractions and may lead to some issues if you are using the same data source elsewhere.

Instead, you can easily extend the ComboBox to show a "Please select" message when it has no item selected.

I blogged about this issue and provided the code here : http://www.byteauthor.com/2010/08/inner-label-in-combobox/

Upvotes: 4

Fredrik Mörk
Fredrik Mörk

Reputation: 158289

When you use databinding, you cannot "manually" add or remove items. The only way to achieve what you want using databinding is to insert a row first in the DataTable with the desired value, or to populate the combobox by code (add the "Select employee" item and then iterate of the the DataTable rows to add the records).

Perhaps something like this could work:

// create new row for "Select employee"
DataRow row = ds.Tables["emp"].NewRow();
row["empid"] = -1;
row["empname"] = "Select employee";
// insert the row at the top of the table
ds.Tables["emp"].Rows.InsertAt(row, 0);
// do the databinding
cbemp.ValueMember = "empid";
cbemp.DisplayMember = "empname";
cbemp.DataSource = ds.Tables["emp"];

I don't use databinding much, so there may be drawbacks with this that I am unaware of (but I am confident that the community will point that out in that case).

Upvotes: 8

Rune Grimstad
Rune Grimstad

Reputation: 36300

When your control is data bound you cannot add items manually I think.

To work around this problem you could either add a new item to your data source, or you could add the items manually.

Upvotes: 0

MartW
MartW

Reputation: 12538

I think you'd have to add it to the underlying datatable (ds.Tables["emp"]) for it to appear as an entry in the list when you're using databound controls.

Upvotes: 0

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