insert multiple checkboxlist values in database using asp.net

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ASP.NET4

<asp:CheckBoxList ID="CheckBoxList1" runat="server"
            RepeatDirection="Horizontal">
            <asp:ListItem>A</asp:ListItem>
            <asp:ListItem>B</asp:ListItem>
            <asp:ListItem>C</asp:ListItem>
            <asp:ListItem>D</asp:ListItem>
        </asp:CheckBoxList>
        <asp:CheckBoxList ID="CheckBoxList2" runat="server"
            RepeatDirection="Horizontal">
            <asp:ListItem>F</asp:ListItem>
            <asp:ListItem>G</asp:ListItem>
            <asp:ListItem>H</asp:ListItem>
            <asp:ListItem>I</asp:ListItem>
        </asp:CheckBoxList>

I want to insert the checkboxlist values using C# in database how can i acheive so

as i have the following code for single checkboxlist1 how can i do for the multiple checkboxlist1 and checkboxlist2 , My code is as

string con = ConfigurationManager.ConnectionStrings["check"].ConnectionString;
        var sSkill = "";
     
        CheckBoxList project = FindControl("CheckBoxList1") as CheckBoxList;
        foreach (ListItem oItem in project.Items)
        {
            if (oItem.Selected)
            {
                if (sSkill.Length == 0)
                    sSkill = oItem.Value;
                else
                    sSkill = sSkill + " " + oItem.Value;
            }
        }
        if (sSkill != "")
        {
            SqlConnection sqlcon = new SqlConnection(con);
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = sqlcon;
            cmd.CommandType = CommandType.Text;
            cmd.CommandText = "INSERT INTO [tablename] (field1 , field2)values(@skill,@text1) , (@skill,@text2 )";
            cmd.Parameters.AddWithValue("@skill", sSkill);
            cmd.Parameters.AddWithValue("@text1", TextBox1.Text);
            cmd.Parameters.AddWithValue("@text2", TextBox2.Text);
            sqlcon.Open();
            cmd.ExecuteNonQuery();
            Label1.Text = sSkill + " was saved sucessesfully";
            sqlcon.Close();
        }