DropDownList控件绑定数据库后，下拉列表没有内容？？！！

[hao19851986]

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{

if (!Page.IsPostBack)
{
Message get = new Message();
DataSet set = get.GetMessage();
this.DropDownList1.DataSource = set;
this.DropDownList1.DataValueField = "ID";
this.DropDownList1.DataTextField = "Title";
this.DropDownList1.DataBind();
}
}

-----------------------------------------------------------------------------------------------------
public DataSet GetMessage()
{
string connectionString = ConfigurationManager.ConnectionStrings["SQLCONNECTIONSTRING"].ConnectionString;
SqlConnection con = new SqlConnection(connectionString);

string cmdText = "select Title,ID from Message";
SqlDataAdapter sda = new SqlDataAdapter(cmdText,con);
DataSet ds = new DataSet();
try
{
con.Open();
sda.Fill(ds);
}
finally
{
con.Close();
}
return ds;
}


调试时，DropDownList下拉列表没有内容，请各位高手指点！！（数据库连接是没有问题的。）

[hao19851986]

补充：（Default.aspx文件）


<br />
<asp:DropDownList ID="DropDownList1" runat="server"
onselectedindexchanged="DropDownList1_SelectedIndexChanged">

</asp:DropDownList>
<br />

[以专业开发人员为伍]

[Quote=引用楼主 的回复:]
protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{

if (!Page.IsPostBack)
{
Message get = new Message();
DataSet set = get.GetMessage();
this.DropDownLi……
[/Quote]

这应该是在 page_load 或者 paeg_prerender 中的代码吧？

[hao19851986]

在Default.aspx.cs中是这样的，正确吗？

public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{

}

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{

if (!Page.IsPostBack)
{
Message get = new Message();
DataSet set = get.GetMessage();
this.DropDownList1.DataSource = set;
this.DropDownList1.DataValueField = "ID";
this.DropDownList1.DataTextField = "Title";
this.DropDownList1.DataBind();
}
}
}

[huli304]

在Default.aspx.cs中是这样的，正确吗？

public partial class _Default : System.Web.UI.Page
{
  protected void Page_Load(object sender, EventArgs e)
  {

  }

  protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
  {

  if (!Page.IsPostBack)
  {
  Message get = new Message();
  DataSet set = get.GetMessage();
  this.DropDownList1.DataSource = set.Tables[0];
  this.DropDownList1.DataValueField = "ID";
  this.DropDownList1.DataTextField = "Title";
  this.DropDownList1.DataBind();
  }
  }
}

[hao19851986]

还是不行！

[大渣吼吾系渣渣辉]

1.我想问，你加载的时候下拉根本没有绑定任何东西，那么 DropDownList1_SelectedIndexChanged 这个有什么用，无语
这样写：
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)//首次加载时绑定
{
Message get = new Message();
DataSet set = get.GetMessage();
this.DropDownList1.DataSource = set;
this.DropDownList1.DataValueField = "ID";
this.DropDownList1.DataTextField = "Title";
this.DropDownList1.DataBind();
}
}

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{

//改变选择后，执行其他操作
}

[dusth]

if (!Page.IsPostBack)
{
Message get = new Message();
DataSet set = get.GetMessage();
this.DropDownList1.DataSource = set;
this.DropDownList1.DataValueField = "ID";
this.DropDownList1.DataTextField = "Title";
this.DropDownList1.DataBind();

DropDownList1.Items.Insert(0, "请选择");

}

[孫大聖]

[Quote=引用 5 楼 的回复:]

还是不行！
[/Quote]

你断点调试下DataSet里面有只吗？？
我觉得你绑定的数据源应该是一个表。而不是DataSet
this.DropDownList1.DataSource = set.Tables[0];

[骑着蜗牛去爬山]

if (!Page.IsPostBack)
{
Message get = new Message();
DataSet set = get.GetMessage();
this.DropDownList1.DataSource = set;
this.DropDownList1.DataValueField = "ID";
this.DropDownList1.DataTextField = "Title";
this.DropDownList1.DataBind();
}
放到pageload里试试

[杰拉尔]

在Default.aspx.cs中是这样的，正确吗？

public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{

BindDDL();

}



}
protected void BindDDL()
{
Message get = new Message();
DataSet set = get.GetMessage();
this.DropDownList1.DataSource = set;
this.DropDownList1.DataValueField = "ID";
this.DropDownList1.DataTextField = "Title";
this.DropDownList1.DataBind();

}

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
BindDDL();


}
}

[hao19851986]

应该按6楼和8楼的方法来调试，可以了！谢谢！！！

现在还有一个问题，怎么在第一次加载时DropDownList1初始值为 “请选择” ？？？

[牛哥_]

[Quote=引用 6 楼 的回复:]

1.我想问，你加载的时候下拉根本没有绑定任何东西，那么 DropDownList1_SelectedIndexChanged 这个有什么用，无语
这样写：
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)//首次加载时绑定
{
Message get = new ……
[/Quote]


看这个 肯定行 在页面加载的时候 查询绑定 要不然怎么实现

[dusth]

[Quote=引用 12 楼 的回复:]
在Default.aspx.cs中是这样的，正确吗？

public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{

BindDDL();

}
……
[/Quote]



为何非要
protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
BindDDL();


}

[春天的气息]

给你一个我通用的绑定吧，字段，表自定义。

  /// <summary>
    /// 绑定dropdownlist字段方法
    /// </summary>
    /// <param name="ddname">dwopdownlist控件名称</param>
    /// <param name="field">要绑定的字段</param>
    /// <param name="tablename">表名</param>
    public void BindDropDownList(DropDownList ddname, string field, string tablename, string typeid)
    {
        try
        {

            string sql = "select " + field + "  from  " + tablename + " where typeid='" + typeid + "'";
            DataSet set = DBClass.GetTableData(sql, "sql");
            ddname.DataSource = set;
            ddname.DataTextField = field;
            ddname.DataBind();
            ddname.Items.Insert(0, new ListItem("请选择...", ""));

        }
        catch (Exception f)
        {
            error.alter(f.Message);
        }
    }

GetTableData 是生成dataset的小方法，

[春天的气息]

  public static DataSet GetTableData(string sql, string tablename)
    {


        SqlConnection con = new SqlConnection(connString);
        SqlDataAdapter Sdr = new SqlDataAdapter(sql, con);
        con.Open();
        DataSet ds = new DataSet();
        Sdr.Fill(ds, tablename);
        return ds;
        con.Close();
    }

GetTableData也给你，呵呵，可以了吧，上面的sql由你改，想怎样用就怎样用。

[xiaowang3266]

开源了,学习了！！！

[lovebaby]

DropDownList1_SelectedIndexChanged本身应该是回发时产生的吧，if (!Page.IsPostBack)是判断页面第一次加载执行，两者不矛盾吗？