How to insert new item in a combobox

Question

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 AvtobusiNOVI 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

Jignesh Trivedi · 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 AvtobusiNOVI 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.

Nel · Answer

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

Nel · Answer

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.

Vulpes · Answer

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;

Nel · Answer

Now I receive error: Column 'GBR' does not allow nulls.

Jignesh Trivedi · Answer

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.