comboBox抉择数据源

comboBox选择数据源
comboBox1.DataSource = dt;
//comboBox1.DisplayMember = "TABLE_name";
comboBox1.ValueMember = "TABLE_name"; //用ValueMember后, comboBox1.SelectedValue.Trim() 可以获取信息,DisplayMember不行
string file = comboBox1.SelectedValue.ToString().Trim();