ArrayList绑定问题，代码如下

[罗卜基斯]

SqlConnection conn = new SqlConnection(connstr);
SqlCommand cmd = new SqlCommand();

cmd.CommandText = "select * from authors";

conn.Open();
cmd.Connection = conn;
SqlDataReader read = cmd.ExecuteReader(CommandBehavior.CloseConnection);
ArrayList list = new ArrayList();
while (read.Read())
{
Author au = new Author();
au.AuthorID = read[0].ToString();
au.AuthorLastName = read[1].ToString();
au.AuthorFirstName = read[2].ToString();
au.AuthorPhone = read[3].ToString();
list.Add(au);
}
GridView1.DataSource = list;
GridView1.DataBind();
read.Close();
cmd.Dispose();
conn.Close();


但是显示的结果是这样的


AuthorID AuthorLastName AuthorFirstName AuthorPhone
998-72-3567 Ringer Albert 801 826-0752
998-72-3567 Ringer Albert 801 826-0752
998-72-3567 Ringer Albert 801 826-0752
998-72-3567 Ringer Albert 801 826-0752
998-72-3567 Ringer Albert 801 826-0752
998-72-3567 Ringer Albert 801 826-0752
998-72-3567 Ringer Albert 801 826-0752
998-72-3567 Ringer Albert 801 826-0752
998-72-3567 Ringer Albert 801 826-0752
998-72-3567 Ringer Albert 801 826-0752
998-72-3567 Ringer Albert 801 826-0752
998-72-3567 Ringer Albert 801 826-0752
998-72-3567 Ringer Albert 801 826-0752
998-72-3567 Ringer Albert 801 826-0752
998-72-3567 Ringer Albert 801 826-0752
998-72-3567 Ringer Albert 801 826-0752
998-72-3567 Ringer Albert 801 826-0752
998-72-3567 Ringer Albert 801 826-0752
998-72-3567 Ringer Albert 801 826-0752
998-72-3567 Ringer Albert 801 826-0752
998-72-3567 Ringer Albert 801 826-0752
998-72-3567 Ringer Albert 801 826-0752
998-72-3567 Ringer Albert 801 826-0752
求解答，是原因

[子夜__]

 protected void Page_Load(object sender, EventArgs e)
    {
        DataTable dt = new DataTable();
        string sql = "select * from authors";
        dt = ReturnDataTable(sql);
        List<Author> lt = new List<Author>();
        if (dt.Rows.Count > 0)
        {
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                Author au = new Author();
                au.AuthorID = read[0].ToString();
                au.AuthorLastName = read[1].ToString();
                au.AuthorFirstName = read[2].ToString();
                au.AuthorPhone = read[3].ToString();
                list.Add(au);
            }
            GridView1.DataSource = list;
            GridView1.DataBind();  
        }

    }
    public static DataTable ReturnDataTable(string cmdtext)
    {
        SqlConnection cn = new SqlConnection();
        cn.ConnectionString = "数据库连接字符串";
        DataTable dt = new DataTable();
        SqlCommand cmd = new SqlCommand();
        cmd = new SqlCommand(cmdtext, cn);
        cmd.CommandType = CommandType.Text; ;
        SqlDataReader dr = null;
        using (dr = cmd.ExecuteReader(CommandBehavior.CloseConnection))
        {
            dt.Load(dr);
        }
        return dt;
    }

[子夜__]

确保数据库里没重复数据

[罗卜基斯]

为什么不能直接从DataReader读取呢，而是要换成DataTable去做呢？

[子夜__]

[Quote=引用 3 楼 darrren2185 的回复:]

为什么不能直接从DataReader读取呢，而是要换成DataTable去做呢？
[/Quote]
都可以

[罗卜基斯]

for (int i = 0; i < dt.Rows.Count; i++)
{
Author au = new Author();
au.AuthorID = read[0].ToString();
au.AuthorLastName = read[1].ToString();
au.AuthorFirstName = read[2].ToString();
au.AuthorPhone = read[3].ToString();
list.Add(au);
}
GridView1.DataSource = list;
GridView1.DataBind();

此处代码中，read对象已经关闭，无法读取meta data数据，故会显示错误

[q107770540]

单步调试查看 SqlDataReader read = cmd.ExecuteReader(CommandBehavior.CloseConnection);
的返回值

[罗卜基斯]

问题我读取Read对象时，就会显示重复的一条记录啊，上面显示的那样

[罗卜基斯]

[Quote=引用 6 楼 q107770540 的回复:]

单步调试查看 SqlDataReader read = cmd.ExecuteReader(CommandBehavior.CloseConnection);
的返回值
[/Quote]
返回值是对的，只是没执行循环的时候，list.add（author）中已经存储的author对象也发生改变

[罗卜基斯]

[Quote=引用 1 楼 wxr0323 的回复:]

C# code
protected void Page_Load(object sender, EventArgs e)
{
DataTable dt = new DataTable();
string sql = "select * from authors";
dt = ReturnDataTable(sql);
L……
[/Quote]

你给的代码结局是一样的，也是

AuthorID AuthorLastName AuthorFirstName AuthorPhone
998-72-3567 Ringer Albert 801 826-0752
998-72-3567 Ringer Albert 801 826-0752
998-72-3567 Ringer Albert 801 826-0752
998-72-3567 Ringer Albert 801 826-0752
998-72-3567 Ringer Albert 801 826-0752
998-72-3567 Ringer Albert 801 826-0752
。。。。。。。。。。。。。。

[子夜__]

晕死。。。

Author au = new Author();
au.AuthorID = read[0].ToString();
au.AuthorLastName = read[1].ToString();
au.AuthorFirstName = read[2].ToString();
au.AuthorPhone = read[3].ToString();
list.Add(au);

写错了 直接复制你的。。

[子夜__]

哎

直接复制你的

protected void Page_Load(object sender, EventArgs e)
    {
        DataTable dt = new DataTable();
        string sql = "select * from authors";
        dt = ReturnDataTable(sql);
        List<Author> lt = new List<Author>();
        if (dt.Rows.Count > 0)
        {
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                Author au = new Author();
                au.AuthorID = dt.Rows[i][0].ToString();
                au.AuthorLastName = dt.Rows[i][1].ToString();
                au.AuthorFirstName = dt.Rows[i][2].ToString();
                au.AuthorPhone = dt.Rows[i][3].ToString();
                list.Add(au);
            }
            GridView1.DataSource = list;
            GridView1.DataBind();  
        }

    }
    public static DataTable ReturnDataTable(string cmdtext)
    {
        SqlConnection cn = new SqlConnection();
        cn.ConnectionString = "数据库连接字符串";
        DataTable dt = new DataTable();
        SqlCommand cmd = new SqlCommand();
        cmd = new SqlCommand(cmdtext, cn);
        cmd.CommandType = CommandType.Text; ;
        SqlDataReader dr = null;
        using (dr = cmd.ExecuteReader(CommandBehavior.CloseConnection))
        {
            dt.Load(dr);
        }
        return dt;
    }
    public static int ExecuteNonQuery(string cmdtext)
    {
        SqlConnection cn = new SqlConnection();
        cn.ConnectionString = "链接字符串";
        cn.Open();
        int value;
        try
        {
            SqlCommand cmd = new SqlCommand(cmdtext, cn);
            value = cmd.ExecuteNonQuery() > 0 ? 1 : 0;
        }
        catch (Exception ex)
        {
            throw ex;
        }
        finally
        {
            if (cn.State == ConnectionState.Open)
            {
                cn.Close();
            }
        }
        return value;
    }

这样

[罗卜基斯]

List<Author> lt = new List<Author>();
if (dt.Rows.Count > 0)
{
for (int i = 0; i < dt.Rows.Count; i++)
{
Author au = new Author();
au.AuthorID = dt.Rows[i][0].ToString();
au.AuthorLastName = dt.Rows[i][1].ToString();
au.AuthorFirstName = dt.Rows[i][2].ToString();
au.AuthorPhone = dt.Rows[i][3].ToString();
list.Add(au); //每执行到这步的时候先前存的值也改变呢？？
}

[罗卜基斯]

怎么没有解决啊

[罗卜基斯]

估计没有下文呢

[子夜__]

[Quote=引用 12 楼 darrren2185 的回复:]

List<Author> lt = new List<Author>();
if (dt.Rows.Count > 0)
{
for (int i = 0; i < dt.Rows.Count; i++)
{
Author au = new Author();
……
[/Quote]
如果你数据库里的记录是不重复的 那么这个值必须改变。

[学会思考]

哇哈哈，LZ英明啊，跟我犯同一个错误，把实例化的对象放在FOR循环里面，每一次循环都是一个新的对象，你说里面能有几条数据？

[学会思考]

Author au = new Author();//为啥不这么写
for (int i = 0; i < dt.Rows.Count; i++)
{

au.AuthorID = read[0].ToString();
au.AuthorLastName = read[1].ToString();
au.AuthorFirstName = read[2].ToString();
au.AuthorPhone = read[3].ToString();
list.Add(au);
}
GridView1.DataSource = list;
GridView1.DataBind();

[罗卜基斯]

[Quote=引用 14 楼 wxr0323 的回复:]

引用 12 楼 darrren2185 的回复:

List<Author> lt = new List<Author>();
if (dt.Rows.Count > 0)
{
for (int i = 0; i < dt.Rows.Count; i++)
{
Author au = new Author();
……

如果你数据库里的记录是不重复的 那么这个值必须改变。
[/Quote] 我用的Sql 2000 pubs数据库中的authors，没有重复的数据啊

[罗卜基斯]

[Quote=引用 16 楼 tomegm 的回复:]

Author au = new Author();//为啥不这么写
for (int i = 0; i < dt.Rows.Count; i++)
{

au.AuthorID = read[0].ToString();
au.AuthorLastName = read[1].ToString();
au.AuthorFirstName = read[2……
[/Quote]

汗～～～～一样的据结果，你那种方式虽说是放在循环外面，作为对象始终只有一个啊。在循环中是重新分配了内存空间来存储的。