如何能去除下拉列表里面的重复值

Question

请问一下，我的form_load里面，写了连接数据库设备表的代码，用于实现一启动，下拉表combobox即连接设备所属的车间名称，但该列所属的车间名称有很多重复值，请问怎么能去除这些个重复值呢，并实现按下拉表的车间名称，查询该车间内的设备信息，相关截图与部分form_load的代码如下；

```c#

            SqlDataAdapter sda = new SqlDataAdapter();

            DataSet ds = new DataSet();

            DataTable dt = new DataTable();

            //声明一个SQLcommand对象

            SqlCommand sqlcmd = new SqlCommand("SELECT * FROM b_EquipmentInfo", conn);


            //执行查询语句
            sda.SelectCommand = sqlcmd;


            //调用DataAdapter对象的Fill（）方法来填充数据集
            sda.Fill(ds, "b_EquipmentInfo");


            //绑定combobox的数据集
            combobox1DataTable.DataSource = ds.Tables["b_EquipmentInfo"];

            //选定combobox显示的成员及将Name这一列显示在combobox中
            combobox1DataTable.DisplayMember = "Plinename";

            //combobox的实际取值
            combobox1DataTable.ValueMember = "Plinecode";

以下是点击查询按钮的代码；

```c#
   conn = new SqlConnection("server=ip;database=db;user=sa;password=1123");

               conn.Open();

               //查询条件      
               SqlString = "select EquipmentCode,EquipmentName,EquipmentType,EquipmentAddress,Manufacturer,PlineName,EquipmentState from b_EquipmentInfo where PlineName = '" + combobox1DataTable.Text + "' "; //配置了与下拉列表绑定，按其查询分类显示；
               //加载数据并显示
               try
               {
                   //查询条件和SqlConnection连接
                   SqlCommand cmd = new SqlCommand(SqlString, conn);
                   //数据适配器
                   SqlDataAdapter sda = new SqlDataAdapter();
                   sda.SelectCommand = cmd;
                   //DataTable存储数据
                   DataTable dt = new DataTable();
                   sda.Fill(dt);
                   dataGridView1.DataSource = dt;
               }
               catch
               { }
               finally
               {
                   conn.Close();

Answer 1

若改为去重语句后“SELECT distinct Plinename FROM b_EquipmentInfo”，其的错误提示如下：在 System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
InnerException:

该错误提示，对应是这条语句 combobox1DataTable.ValueMember = "Plinecode"，请问如何处理呢，再指导一下，谢谢；