How to insert new item in a combobox

Nel

Hello,
I fill the combobox on the following way

OleDbDataAdapter datAd = new OleDbDataAdapter();
                datAd.SelectCommand = new OleDbCommand();
                datAd.SelectCommand.Connection = conn;
                datAd.SelectCommand.CommandText = "SELECT NOVI.GBR FROM NOVI WHERE NOVI.GBR NOT IN (SELECT Avtobusi.Garbr FROM Avtobusi) UNION (select Avtobusi.Garbr from Avtobusi,NOVI where Avtobusi.Sloboden=true)";

                datAd.SelectCommand.ExecuteNonQuery();

_dataset.Clear();
datAd.Fill(_dataset, "NOVI");

comboBox1.DataSource = _dataset.Tables["NOVI"];
comboBox1.DisplayMember = "GBR";

and I want to insert an empty field in the beggining of the combobox.
I tried with this:
comboBox1.Items.Add(" ");
comboBox1.SelectedIndex = comboBox1.Items.Count - 1;
but it can't be done like this. The combobox remain the same, without the empty item at the beginning.

Can anybody help me please?
Thanks

6 Replies

Know the answer? Post it — somebody with the same question will find it here.

Jignesh Trivedi14y ago
Accepted answer
hi,

now you change you query.
SELECT cast(NOVI.GBR FROM NOVI WHERE NOVI.GBR NOT IN (SELECT Avtobusi.Garbr FROM Avtobusi)
UNION
(select cast(Avtobusi.Garbr from Avtobusi,NOVI where Avtobusi.Sloboden=true)

Cast your interger value to string and try...

DataTable dt = _dataset.Tables["NOVI"];
DataRow dradd = dt.NewRow();
dradd["GBR"] = " "; // a single space
dt.Rows.InsertAt(dradd, 0); // place at top
comboBox1.DataSource = dt;
comboBox1.DisplayMember = "GBR";
hope this help.
Nel14y ago
Thank you to both of you. I have left my select as it was written before, and used the rest of the code for the table
Nel14y ago
OK, thanks Vulpes, I put 0 instead of "", since the type of the column values is int. But now I see only the 0 in the combobox, not the whole column of the table NOVI.
Vulpes14y ago
Try instead:

DataTable dt = _dataset.Tables["NOVI"];
DataRow dradd = dt.NewRow();
dradd["GBR"] = " "; // a single space
dt.Rows.InsertAt(dradd, 0); // place at top
comboBox1.DataSource = dt;
comboBox1.DisplayMember = "GBR";
Nel14y ago
Now I receive error: Column 'GBR' does not allow nulls.
Jignesh Trivedi14y ago
hi,

We cannot add new item in Item source.
but yes you can add your new row in datasouse i.e. in your data table.

DataTable dt = _dataset.Tables["NOVI"];
comboBox1.DataSource = dt;
comboBox1.DisplayMember = "GBR";

DataRow dradd = dt.NewRow();
dt.Rows.Add(dradd);

hope this help.