How to use cascading dropdownlist, error Procedure or function Tech_sup has too many arguments specified.

i want to use cascading dropdownlist its like this

i have one dropdown \

Hardware

software

Network

when i click network its should only display dropdown list of network problems same for software and Hardware

i am trying like this

Aspx

<pre lang="HTML">

 <asp:DropDownList ID="PRB_type_ddl" runat="server"
                    DataTextField="prob_type"
                    DataValueField="prob_type" Height="20px" Width="114px"
    onselectedindexchanged="DropDownList3_SelectedIndexChanged1" AutoPostBack="True"
                    >
                            <asp:ListItem>--Select--</asp:ListItem>
                            <asp:ListItem>Hardware</asp:ListItem>
                            <asp:ListItem>Software</asp:ListItem>
                            <asp:ListItem>Network</asp:ListItem>
                        </asp:DropDownList>
                        <br />


            </td>
            <td class="style33">
        <span class="style28">
                        <asp:DropDownList ID="Hard_ddl" runat="server"
                            DataTextField="Hardware"
                            DataValueField="Hardware" DataSourceID="SqlDataSource3">
                        </asp:DropDownList>


                <asp:SqlDataSource ID="SqlDataSource3" runat="server"
                    ConnectionString="<%$ ConnectionStrings:con %>"
                    SelectCommand="SELECT [Hardware] FROM [p_type]"></asp:SqlDataSource>


                <asp:DropDownList ID="Soft_ddl" runat="server"
                   DataTextField="Software"
                    DataValueField="Software" DataSourceID="SqlDataSource5">
                </asp:DropDownList>
                <asp:SqlDataSource ID="SqlDataSource5" runat="server"
                    ConnectionString="<%$ ConnectionStrings:con %>"
                    SelectCommand="SELECT [Software] FROM [p_type]"></asp:SqlDataSource>
                <asp:DropDownList ID="OP_ddl" runat="server"
                    DataTextField="Operating_system"
                    DataValueField="Operating_system" DataSourceID="SqlDataSource6">
                </asp:DropDownList>

                <asp:SqlDataSource ID="SqlDataSource7" runat="server"
                    ConnectionString="<%$ ConnectionStrings:con %>"
                    SelectCommand="SELECT [Net_work] FROM [p_type]"></asp:SqlDataSource>
c#

protected void DropDownList3_SelectedIndexChanged1(object sender, EventArgs e)
    {

        if (PRB_type_ddl.SelectedValue == "Hardware")
        {
            Hard_ddl.Visible = true;
            Soft_ddl.Visible = false;
            NET_ddl.Visible = false;
            Soft_ddl.SelectedIndex = -1;
            NET_ddl.SelectedIndex = -1;



        }


        else if (PRB_type_ddl.SelectedValue == "Software")
        {
            Soft_ddl.Visible = true;
            NET_ddl.Visible = false;
            Hard_ddl.Visible = false;

            Hard_ddl.SelectedIndex = -1;
            NET_ddl.SelectedIndex = -1;
        }
        else
        {
            NET_ddl.Visible = true;
            Hard_ddl.Visible = false;

            Soft_ddl.Visible = false;

            Soft_ddl.SelectedIndex = -1;
            Hard_ddl.SelectedIndex = -1;
        }

    }




                    con.Open();
                    SqlCommand cmd = new SqlCommand();
                    cmd.CommandType = CommandType.StoredProcedure;
                    cmd.CommandText = "Tech_sup";
                    cmd.Parameters.AddWithValue("@Build_name", Build.Text);
                    cmd.Parameters.AddWithValue("@Dept", DropDownList2.Text);
                     if (string.IsNullOrEmpty(Hard_ddl.Text))
                    {
                        cmd.Parameters.Add(new SqlParameter("@P_type", DBNull.Value.ToString()));
                    }
                    else
                    {
                        cmd.Parameters.Add(new SqlParameter("@P_type", Hard_ddl.Text));
                    }
                    if (string.IsNullOrEmpty(Soft_ddl.Text))
                    {
                        cmd.Parameters.Add(new SqlParameter("@P_type", DBNull.Value.ToString()));
                    }
                    else
                    {
                        cmd.Parameters.Add(new SqlParameter("@P_type", Soft_ddl.Text));
                    }

                    if (string.IsNullOrEmpty(NET_ddl.Text))
                    {
                        cmd.Parameters.Add(new SqlParameter("@P_type", DBNull.Value.ToString()));
                    }
                    else
                    {
                        cmd.Parameters.Add(new SqlParameter("@P_type", NET_ddl.Text));
                    }
                    cmd.Connection = con;
                    cmd.ExecuteNonQuery();
                    con.Close();