我如何... Dropdownlist过滤器在ASP.net中使用层架构 [英] How do I...Dropdownlist filter use layer architecture in ASP.net

问题描述

国家/地区aCountry = 新国家/地区（）; 
  int  countryId = aCountry.CountryId; 
  string  quary =   SELECT StateId，StateName FROM tCountryState WHERE countryId =' + countryId +  '; 
 SqlConnection con =  new  SqlConnection（连接）; 
 con.Open（）; 
 DataSet ds =  new  DataSet（）; 
 SqlDataAdapter da =  new  SqlDataAdapter（quary，con）; 
 da.Fill（ds）; 
 con.Close（）; 
  return  ds; 

[我的字符串问题在哪里？ ????????????????????????????????????????????????????????????????????????????????????????????????? b $ b

国家/地区aCountry = 新国家/地区（）; 
  int  countryId = aCountry.CountryId; 

而 aCountry 是 new Country（）; ，你怎么会得到 aCountry.CountryId ，它可能会返回null。



你的第二个错误是：

  string  quary =   SELECT StateId，StateName FROM tCountryState WHERE countryId =' + countryId +  '; 

here countryId 是 int ，您也没有将其转换为 string 。你应该写成：

  string  quary =   SELECT StateId，StateName FROM tCountryState WHERE countryId =' + Convert.ToString（countryId）+  '; 

从此示例中获取提示： http://www.aspsnippets.com/Articles/Creating-Cascading-DropDownLists-in-ASP.Net.aspx [ ^

Country aCountry=new Country();
            int countryId = aCountry.CountryId;
            string quary = "SELECT StateId,StateName FROM tCountryState WHERE countryId='"+countryId+"'";
            SqlConnection con = new SqlConnection(connection);
            con.Open();
            DataSet ds = new DataSet();
            SqlDataAdapter da = new SqlDataAdapter(quary, con);
            da.Fill(ds);
            con.Close();
            return ds;

[Where my string problem?????????????]

解决方案

Hi,
Here is your code:

Country aCountry=new Country();
int countryId = aCountry.CountryId;

While aCountry is new Country();, how would you get aCountry.CountryId, it might be returning null.

Your second mistake is :

string quary = "SELECT StateId,StateName FROM tCountryState WHERE countryId='"+countryId+"'";

here countryId is int and you are also not converting it to string. you should write as :

string quary = "SELECT StateId,StateName FROM tCountryState WHERE countryId='"+Convert.ToString(countryId)+"'";

Take cue from this example: http://www.aspsnippets.com/Articles/Creating-Cascading-DropDownLists-in-ASP.Net.aspx[^]

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