how to bind data

I have three drop downs -bounded with object datasources,
by default each drop down shows all countries , cites and distt.
When user select country only related cities should show under city dropdown. and when user select city-only distt related to city show up
Here's the code

Code:

---

STATE:
              <asp:DropDownList ID="ddlSt" runat="server"
              DataSourceID="OdsState"
              DataTextField="STATE_COUNTRY_NAME"
              DataValueField="STATE_COUNTRY_CODE"
              AutoPostBack="True"  OnInit="ddlst_Init" 
                onselectedindexchanged="ddlSt_SelectedIndexChanged" AppendDataBoundItems="true">
                <asp:ListItem Text="" Value="0"></asp:ListItem>
          </asp:DropDownList>
          <asp:ObjectDataSource ID="OdsState" runat="server"
              OldValuesParameterFormatString="original_{0}" SelectMethod="GetData"
              TypeName="stateTableAdapters.STATE_COUNTRYTableAdapter">
              <SelectParameters>
                  <asp:ControlParameter ControlID="ddlyr" Name="FromYear"
                      PropertyName="SelectedValue" Type="Decimal" DefaultValue="null" />
                  <asp:ControlParameter ControlID="ddlTo" Name="ToYear"
                      PropertyName="SelectedValue" Type="Decimal" />
                  <asp:ControlParameter ControlID="RBl1" Name="mytype"
                      PropertyName="SelectedValue" Type="String" />
              </SelectParameters>
          </asp:ObjectDataSource>
               
            <asp:ObjectDataSource ID="SrcCty" runat="server"
                OldValuesParameterFormatString="original_{0}" SelectMethod="GetData"
                TypeName="stateTableAdapters.CityTableAdapter">
                <SelectParameters>
                    <asp:ControlParameter ControlID="ddlSt" Name="MyState"
                        PropertyName="SelectedValue" Type="String" DefaultValue="null" />
                    <asp:ControlParameter ControlID="RBl1" Name="mytype"
                        PropertyName="SelectedValue" Type="String" />
                    <asp:ControlParameter ControlID="ddlyr" Name="FromYear"
                        PropertyName="SelectedValue" Type="Decimal" />
                    <asp:ControlParameter ControlID="ddlTo" Name="ToYear"
                        PropertyName="SelectedValue" Type="Decimal" />
                </SelectParameters>
            </asp:ObjectDataSource>
            CITY:
            <asp:DropDownList ID="ddlCity" runat="server" DataSourceID="SrcCty"             
            DataTextField="CITY" DataValueField="STATE_COUNTRY_CODE" OnInit="ddlcity_Init" AppendDataBoundItems="true" >
            <asp:ListItem Text=" " Value="0"></asp:ListItem>
            </asp:DropDownList>  &nbsp; &nbsp;
           
            <asp:ObjectDataSource ID="SrcDistt" runat="server"
                OldValuesParameterFormatString="original_{0}" SelectMethod="GetData"
                TypeName="stateTableAdapters.DisttTableAdapter">
                <SelectParameters>
                    <asp:ControlParameter ControlID="RBl1" DefaultValue="&quot;G&quot;"
                        Name="mytype" PropertyName="SelectedValue" Type="String" />
                    <asp:ControlParameter ControlID="ddlSt"  Name="myState"
                        PropertyName="SelectedValue" Type="String" />
                    <asp:ControlParameter ControlID="ddlyr" Name="FromYear"
                        PropertyName="SelectedValue" Type="Decimal" />
                    <asp:ControlParameter ControlID="ddlTo" DefaultValue="&quot; &quot;"
                        Name="ToYear" PropertyName="SelectedValue" Type="Decimal" />
                    <asp:ControlParameter ControlID="ddlCity" DefaultValue="null" Name="mycity"
                        PropertyName="SelectedValue" Type="String" />
                </SelectParameters>
            </asp:ObjectDataSource> 
          Cong.Dist:
          <asp:DropDownList ID="ddlCongDistt" runat="server" Width="100" AutoPostBack="true"
              DataSourceID="SrcDistt" DataTextField="congrsnl_district_code"                 
                onselectedindexchanged="ddlCongDistt_SelectedIndexChanged" AppendDataBoundItems="true" >
                <asp:ListItem Text="" Value="0"></asp:ListItem>
                </asp:DropDownList> <br /> <br/>

---

In c#
protected void Page_Prerender(Object sender, EventArgs e)
{
if (!IsPostBack)
{

OdsState.SelectParameters["ToYear"].DefaultValue = null;
SrcCty.SelectParameters["myState"].DefaultValue = null;
SrcDistt.SelectParameters["myState"].DefaultValue = null;
SrcDistt.SelectParameters["mycity"].DefaultValue = null;
}

}
protected void RBl1_SelectedIndexChanged(object sender, EventArgs e)
{


MakeSQL();

}
protected void ddlst_Init(object sender, EventArgs e)
{
ddlSt.Items.Insert(0, new ListItem("--", string.Empty));

}

protected void ddlSt_SelectedIndexChanged(object sender, EventArgs e)
{


sSQL += "AND STATE_COUNTRY_CODE='" + ddlSt.SelectedValue.ToString() + "'";
MakeSQL();
}


protected void ddlcity_Init(object sender, EventArgs e)
{


ddlCity.Items.Insert(0, new ListItem("---", string.Empty));

}


protected void ddlCity_SelectedIndexChanged(object sender, EventArgs e)
{
if (ddlSt.SelectedIndex >= 0)
{
SrcCty.SelectParameters["myState"].DefaultValue = ddlSt.SelectedValue;

}

sSQL += "AND CITY='" + ddlCity.SelectedValue.ToString() + "'";
lblmsg.Text = sSQL;
MakeSQL();
}



protected void ddlCongDistt_SelectedIndexChanged(object sender, EventArgs e)
{
sSQL += "AND congrsnl_district_code ='" + ddlCongDistt.SelectedValue.ToString() + "'";
MakeSQL();
}