UpdateParameter not being passed

//code that changes the parameter values:
  {
        //Find dropdown to get selected Item text  
        DropDownList ddlDvCountry = (DropDownList)
        dvParent.FindControl("ddlCountry");
        string strCountry = ddlDvCountry.SelectedItem.Value;
 
        DropDownList ddlDvState = (DropDownList)
        dvParent.FindControl("ddlState");
        string strState = ddlDvState.SelectedItem.Value;
 
        DropDownList ddlIndustry = (DropDownList)
        dvParent.FindControl("ddlIndustry");
        string strIndustry = ddlIndustry.SelectedItem.Value;
 
        DropDownList ddlMainName = (DropDownList)
        dvParent.FindControl("ddlMainName");
        string strMain = ddlMainName.SelectedItem.Value;
 
        odsParentDetail.UpdateParameters.Remove(odsParentDetail.UpdateParameters["countryID"]);
        odsParentDetail.UpdateParameters.Remove(odsParentDetail.UpdateParameters["stateID"]);
        odsParentDetail.UpdateParameters.Remove(odsParentDetail.UpdateParameters["industryID"]);
        odsParentDetail.UpdateParameters.Remove(odsParentDetail.UpdateParameters["Main_Number"]);
        odsParentDetail.UpdateParameters.Add("countryID", strCountry);
        odsParentDetail.UpdateParameters.Add("stateID", strState);
        odsParentDetail.UpdateParameters.Add("industryID", strIndustry);
        odsParentDetail.UpdateParameters.Add("Main_Number", strMain);
        
   //At this point in debug I can see that all paramters are changed - including Main_Number.
 
}
 
//Beginning of the method that uses the parameters. In debug at the point below I can see that all of the values from above are passed correctly to the method except for Main_Number - which is unchanged.   
 
public bool UpdateParentDetail(int Parent_Number, string Parent_Name, int industryID, decimal countryID, decimal stateID, string Main_Number)
     {
         //do stuff
}