How To Bind Combo Box

private void BindMainAgentInput()
        {
            ddlMainAgentInput.Items.Clear();

            m_oMainAgentCollectionInput.Clear();

            m_oMainAgentCollectionInput.ListMainAgent();
            m_oMainAgentCollectionInput.Sort(SellingAgentCollection.SellingAgentFields.AgentName, true);

            SellingAgent oSellingAgentDefault = new SellingAgent(-1);
            oSellingAgentDefault.AgentCode2AndNameForDDL = RCMS.BusinessLogicLayer.Constanta.Common.const_sSelectOne;
            m_oMainAgentCollectionInput.Insert(0, oSellingAgentDefault);

            ddlMainAgentInput.DisplayMember = "AgentCode2AndNameForDDL";
            ddlMainAgentInput.ValueMember = "SellingAgentId";
            ddlMainAgentInput.DataSource = m_oMainAgentCollectionInput;
            ddlMainAgentInput.Rebind();
            ddlMainAgentInput.SelectedValue = oSellingAgentDefault.SellingAgentId;
        }