为什么没有执行while里面的代码 直接执行return list呢，三个参数的值都获取到了 谁帮解决下 谢谢啊 在线求解~

[frank2828]

/// <summary>
/// 产品分页展示根据ClassName
/// </summary>
/// <param name="pagesize">每页显示多少条</param>
/// <param name="pageindex">当前第几页</param>
/// <returns>返回List<prod_news>集合</returns>
public List<prod_news> ProductFenYeByClassName(int pagesize, int pageindex,string className)
{
try
{
int num = pagesize * pageindex;
string sqlStr = "select top 12 * from prod_news where ID not in (select top " + num + " ID from prod_news order by infotime desc) and ClassName="+className+" order by infotime desc";
OleDbCommand cmd = new OleDbCommand(sqlStr, con);
OleDbParameter par1 = new OleDbParameter("@pagesize", OleDbType.Integer);
OleDbParameter par2 = new OleDbParameter("@pageindex", OleDbType.Integer);
OleDbParameter par3=new OleDbParameter("@ClassName",OleDbType.VarChar);
par1.Value = pagesize;
par2.Value = pageindex;
par3.Value=className;
cmd.Parameters.Add(par1);
cmd.Parameters.Add(par2);
cmd.Parameters.Add(par3);
List<prod_news> list = new List<prod_news>();
con.Open();
OleDbDataReader reader = cmd.ExecuteReader();
while (reader.Read())
{
prod_news prod_news = new prod_news();
prod_news.ID = Convert.ToInt32(reader["ID"]);
prod_news.title = reader["title"].ToString();
prod_news.content = reader["content"].ToString();
prod_news.ClassName = reader["ClassName"].ToString();
prod_news.img = reader["img"].ToString();
prod_news.okay2 = Convert.ToInt32(reader["okay2"]);
prod_news.okay = Convert.ToInt32(reader["okay"]);
prod_news.infotime = Convert.ToDateTime(reader["infotime"]);
prod_news.hits = Convert.ToInt32(reader["hits"]);
prod_news.ok = Convert.ToBoolean(reader["ok"]);
list.Add(prod_news);
}
return list;
}
catch (Exception ec)
{
throw ec;
}
finally
{
con.Close();
}
}


为什么没有执行while里面的代码 直接执行return list呢，三个参数的值都获取到了 谁帮解决下 谢谢啊 在线求解~

[frank2828]

我用的是ACCESS 数据库第一次用 问题肯定还在语句上啊 帮我瞅瞅吧~

[IT-Style]

可能是根据你传入的参数拼接的SQL语句没有查询出数据来.

[frank2828]

是啊 我那条语句查询的结果 list为0，但是那条语句我不知道哪儿错了 ，我连接的是ACCESS 我不熟悉ACCESS啊啊

[facelessvoidhj]

应该是没有查询出来数据，你断点进去看下SQL是怎样的，然后在ACCESS里面执行看看

[frank2828]

select top 12 * from prod_news where ID not in (select top 12 ID from prod_news order by infotime desc) and ClassName=‘检验分析纯水设备’ order by infotime desc


这是断点里的内容，在ACCESS里可以像SQL server一样执行查询码 ，

[kke_007]

没数据肯定是不会执行啊。。

string sqlStr = "select top 12 * from prod_news where ID not in (select top " + num + " ID from prod_news order by infotime desc) and ClassName="+className+" order by infotime desc";
OleDbCommand cmd = new OleDbCommand(sqlStr, con);
OleDbParameter par1 = new OleDbParameter("@pagesize", OleDbType.Integer);
OleDbParameter par2 = new OleDbParameter("@pageindex", OleDbType.Integer);
OleDbParameter par3=new OleDbParameter("@ClassName",OleDbType.VarChar);
par1.Value = pagesize;
par2.Value = pageindex;
par3.Value=className;
cmd.Parameters.Add(par1);
cmd.Parameters.Add(par2);
cmd.Parameters.Add(par3);

SQL 里哪有@pagesize参数等

[facelessvoidhj]

我也接触不多，之前用过一次，好像在“创建”菜单下面 有个什么“查询设计”之类的，你可以自己试试

[facelessvoidhj]

而且如6楼所说，你写的SQL没有用到参数啊，你的本意是这样吧
string sqlStr = "select top @pagesize * from prod_news where ID not in (select top @pageindex ID from prod_news order by infotime desc) and ClassName=@ClassName order by infotime desc";

[frank2828]

int num = pagesize * pageindex;
这个不是吗 我吧传入的2个参数给合成一个了，这样不行吗 我在ACCESS里试过了
select top 12 * from prod_news where ID not in (select top 12 ID from prod_news order by infotime desc) and ClassName=‘检验分析纯水设备’ order by infotime desc
我把ClassName=‘检验分析纯水设备’改成ClassName="检验分析纯水设备"就有结果了 可是 在传入ClassName参数时怎么写才对呢 ~~~

[frank2828]

int num = pagesize * pageindex;头两个参数和成一个查询没问题的 ，就是第三个参数的问题

[facelessvoidhj]

OleDbParameter par1 = new OleDbParameter("@pagesize", OleDbType.Integer);
OleDbParameter par2 = new OleDbParameter("@pageindex", OleDbType.Integer);
OleDbParameter par3=new OleDbParameter("@ClassName",OleDbType.VarChar);
par1.Value = pagesize;
par2.Value = pageindex;
par3.Value=className;
cmd.Parameters.Add(par1);
cmd.Parameters.Add(par2);
cmd.Parameters.Add(par3);
整个注释掉试试