Items collection cannot be modified when the DataSource property is set.

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C#

C#4.0

Hi,
I have an following issue.
Items collection cannot be modified when the DataSource property is set.
I am using Combobox in c#.net windows application.
at form load event following code.

setCombobox_LoadRecords("SELECT ProductName FROM Product_Info", "Product_Info", "ProductName", comboBoxPerticulars);

that calls method below.

public static void setCombobox_LoadRecords(string SQL, string Table, string FieldName, ComboBox combo)
        {
            try
            {
                combo.Items.Clear();
                DataSet dataset = new DataSet();

                Adapter = new SqlDataAdapter();

                connection.setCommand(dataset, Adapter, SQL, Table);
                combo.DataSource = dataset.Tables[0].DefaultView;
                combo.DisplayMember = FieldName;
                combo.ValueMember = FieldName;
                combo.SelectedIndex = -1;

            }
            catch (Exception ex) { ex.ToString(); }
        }

so i want to show Select Text at index -1.
Please help me.