我想知道DBHelper.GetDataSet(string.Format("select * from AreaInfo where ParentID='0'",后面应该加什么

Question

//省市区三级联动
protected void ddlProvince_SelectedIndexChanged(object sender, EventArgs e)
{
DataTable dt = DBHelper.GetDataSet(string.Format("select * from AreaInfo where ParentID='0'",));//下拉列表

        ddlCity.DataSource = dt;
        ddlCity.DataTextField = "AreaName";
        ddlCity.DataValueField = "AreaID";
        ddlCity.DataBind();

        ListItem li = new ListItem("未选择", "0");
        ddlCity.Items.Clear();
        ddlCounty.Items.Insert(0, li);
    }

    protected void ddlCity_SelectedIndexChanged(object sender, EventArgs e)
    {
        DataTable dt = DBHelper.GetDataSet(string.Format("select * from AreaInfo where ParentID='0'",));//下拉列表

        ddlCounty.DataSource = dt;
        ddlCounty.DataTextField = "AreaName";
        ddlCounty.DataValueField = "AreaID";
        ddlCounty.DataBind();

        ListItem li = new ListItem("未选择", "0");
        ddlCounty.Items.Insert(0, li);
    }

Answer 1

DataTable dt = DBHelper.GetDataSet(string.Format("select * from AreaInfo where ParentID='{0}'", ddlCounty.SelectedValue.ToString()));