Código
private void IngresoProveedor_Load(object sender, EventArgs e) { this.ActiveControl = txtnit; cmbdepto.DataSource = carga.cargaDeptos().Tables[0]; cmbdepto.ValueMember = "clave"; cmbdepto.DisplayMember = "nombre"; //cmbdepto.DataBindings(); } private void cmbdepto_SelectedIndexChanged(object sender, EventArgs e) { //cargar el siguiente combobox cmbmpio.DataSource = cargar.selectMpios(Convert.ToInt32 (this.cmbmpio.SelectedValue ) ).Tables[0]; cmbmpio.ValueMember = "clave"; cmbmpio.DisplayMember = "nombre"; }