SqlDataReader指定转换无效的解决方法

//获取最新显示顺序数据
 string str = string.Format(@"if exists(select ShowOrder from GIS_FuncDefaultLayer where GISFuncId = {0})
 select max(ShowOrder) as ShowOrder from GIS_FuncDefaultLayer where GISFuncId ={0}
 else select '0' as ShowOrder", GISFuncId); 
 IDataReader dataReader = helper.ExecuteReader(CommandType.Text, str);
 if (dataReader.Read())//判断当前功能Id下是否有数据
 {
 //读取赋值
 try
 {
 showOrder = dataReader.GetInt32(0);
 
 }
 catch (Exception ex)
 {

 HttpResponseMessage result = new HttpResponseMessage { Content = new StringContent(ex.Message) };
 return result;
 }
 
 }
dataReader.Close();//关闭

//解决
showOrder=int.Parse(dataReader.GetString(0));