C#-这段代码无法正常运行的原因是什么?

出于某种原因,第1节有效,但第2节无效。当以相反的顺序运行时(2在1之前),第1节(附属关系)根本不会运行。所有的数据都是一样的。

//Section 1

            UserService.DsUserAttributes dsAffiliation = us_service.GetUserAttributeDropDown(systemId, "Affiliation");
            Affiliation.DataSource = dsAffiliation.tblDropDownValues;
            Affiliation.DataTextField = "AttrValue";
            Affiliation.DataValueField = "Id";
            Affiliation.DataBind();                

//Section 2                 
            UserService.DsUserAttributes dsCountry = us_service.GetUserAttributeDropDown(systemId, "Country");
            Country.DataSource = dsCountry.tblDropDownValues;
            Country.DataTextField = "AttrValue";
            Country.DataValueField = "Id";
            Country.DataBind();