How to retrieve only selected data from one combo box to another combo box

See more:

C#3.0

.NET3.5

C#

.NET

I am creating desktop application in which i have created a form in which there are three comboboxes namely cboproduct,cborawmaterial_id and cborawmaterial.
I have products namely steamiron,mobile,juicer with respective product id.
I have rawmaterials thermostat,inlay,ic,cuplor,jar,led.

I want that when i select one product at a time from cboproduct,i should get its respective rawmaterials in cborawmaterial.
I created a 2 tables
product_info with field product_id and product
rawmaterial_info with field product_id ,rawmaterial_id and rawmaterial

I tried this coding

SqlConnection con;
           // SqlCommand com;
           String message;
           con = new SqlConnection(@"Data Source=AKMINDER-PC\SQLEXPRESS;Initial Catalog=elin appliances(Comaker of PHILIPS);Integrated Security=true");
           SqlCommand com = new SqlCommand();
           message = "Select product_id, product_name from product_info";
           con.Open();
           DataSet DS = new DataSet();
           SqlDataAdapter DA = new SqlDataAdapter();

           DA.SelectCommand = new SqlCommand(message, con);
           // com.ExecuteNonQuery();

           DA.Fill(DS);
           con.Close();
           if (DS.Tables[0].Rows.Count > 0)
           {
               combo1.DataSource = DS.Tables[0];
               combo1.DisplayMember = "product_name";
               combo1.ValueMember = "product_id";

               //combo1.Items.Insert(0, "--Select--");
           }
           else
           {
               lblMsg.Text = "No product found";
           }

               }
                private void fillrawmaterialid(string proid)

       {
           SqlConnection con;
          // SqlCommand com;
          // String message;
           con=new SqlConnection(@"Data Source=AKMINDER-PC\SQLEXPRESS;Initial Catalog=elin appliances(Comaker of PHILIPS);Integrated Security=true");
           SqlCommand com = new SqlCommand();
           //message = "Select Raw_Material_ID ,Raw_Material from Raw_Info where product_id='"+combo1.SelectedIndex+"'";
           com.Connection = con;
           com.CommandText = "Select Raw_Material_ID ,Raw_Material from Raw_Info where product_id='" + proid + "'";
         com.Parameters.AddWithValue("@proid", proid);

           DataSet DS = new DataSet();
           SqlDataAdapter DA = new SqlDataAdapter();


           DA.SelectCommand = com;
           con.Open();

          // com.ExecuteNonQuery();

           DA.Fill(DS);
           con.Close();
           if (DS.Tables[0].Rows.Count > 0)
           {
               comborawid.DataSource = DS.Tables[0];
               comborawid.DisplayMember = "Raw_Material";
               comborawid.ValueMember = "Raw_Material_ID";

               //combo1.Items.Insert(0, "--Select--");
           }
           else
           {
               lblMsg.Text = "No product found";
           }
private void combo1_SelectedIndexChanged(object sender, EventArgs e)
       {
          string proid=(combo1.SelectedIndex.ToString());
           fillrawmaterialid(proid);


       }

Now with valuemember and Display member i am getting values in combo1 but i also want the list of raw material corressponding to selected index of Combo1 in cborawmaterial.
e.g if I select Product laptop in combo1_SelectedIndexChanged then only I should get specific raw material related to laptop not all rawmaterials which is stored in database
but i am getting whole list of raw material

do tell me about select query ...what change is need?