下拉列表未给出所选值答案

【问题标题】：Dropdownlist not giving selected value下拉列表未给出所选值
【发布时间】：2014-05-14 07:49:58
【问题描述】：

我有这个 aspx 源代码

<tr>
            <td>MatchName</td>
            <td>
                <asp:DropDownList ID="ddlMatchName" runat="server">
                </asp:DropDownList>
            </td>
        </tr>
        <tr>
            <td>Winning Team</td>
            <td>
                <asp:DropDownList ID="ddlWinningTeam" runat="server">
                </asp:DropDownList>
            </td>
        </tr>
        <tr>
            <td>Score</td>
            <td>
                <asp:TextBox ID="txtScore" runat="server"></asp:TextBox>
            </td>
        </tr>
        <tr>
            <td>
                <asp:Button ID="btnSave" runat="server" Text="Save"  OnClick="btnSave_Click" />
            </td>
            <td>
                <asp:Button ID="btnCancel" runat="server" Text="Cancel" OnClick="btnCancel_Click" />
            </td>
        </tr>

C#代码

 protected void Page_Load(object sender, EventArgs e)
    {
        string queryMatchDetail = "select MatchId,MatchName from ADMMasterMatch order by MatchDate";
        ddlMatchName.DataSource = clsNewSqlFunctions.GetSelectedData(queryMatchDetail);
        ddlMatchName.DataTextField = "MatchName";
        ddlMatchName.DataValueField = "MatchId";
        ddlMatchName.DataBind();

        string queryTeamDetail = "SELECT [TeamId],[TeamName] FROM [AdmCurrentEventMasterTeam] order by TeamName";
        ddlWinningTeam.DataSource = clsNewSqlFunctions.GetSelectedData(queryTeamDetail);
        ddlWinningTeam.DataTextField = "TeamName";
        //ddlWinningTeam.DataValueField = "TeamId";
        ddlWinningTeam.DataBind();

    }

    protected void btnSave_Click(object sender, EventArgs e)
    {
        var s = ddlMatchName.SelectedIndex;
        string query = "UPDATE [ADMMasterMatch] SET Winner = '" + ddlWinningTeam.SelectedItem.Text + "' , Score = '" + txtScore.Text + "' Where MatchId ='" + ddlMatchName.SelectedItem.Text +"'";
        clsNewSqlFunctions.ExecuteQuery(query);
    }
    protected void btnCancel_Click(object sender, EventArgs e)
    {
        Response.Redirect("ADMCurrentEventMatchResult.aspx");
    }

这里clsNewSqlFunctions.ExecuteQuery() 和 clsNewSqlFunctions.GetSelectedData() 是执行查询和选择以数据集形式返回数据的数据的方法

在Save_Click 事件中，我正在从下拉列表的选定值更新数据库中的数据，但它没有显示我选定的值
它总是在索引 0 处显示值。在 SelectedText,SelectedItem
请帮我看看我的代码有什么问题

【问题讨论】：

这是因为您在回发时重新绑定了列表 - 查找页面生命周期和 IsPostBack 属性。
一个愚蠢的错误 :p:p 感谢@DaveParsons
您的btnSave_Click 查询已经成熟，可以进行 sql 注入攻击了。
DropDownList lose index after PostBack 的可能重复项
@DaveParsons 这是什么意思，我该如何纠正它

标签： c# asp.net webforms

【解决方案1】：

请将您的下拉列表绑定到!ispostback

 protected void Page_Load(object sender, EventArgs e)
    {
      if(!ispostback)
      {
        string queryMatchDetail = "select MatchId,MatchName from ADMMasterMatch order by MatchDate";
        ddlMatchName.DataSource = clsNewSqlFunctions.GetSelectedData(queryMatchDetail);
        ddlMatchName.DataTextField = "MatchName";
        ddlMatchName.DataValueField = "MatchId";
        ddlMatchName.DataBind();

        string queryTeamDetail = "SELECT [TeamId],[TeamName] FROM [AdmCurrentEventMasterTeam] order by TeamName";
        ddlWinningTeam.DataSource = clsNewSqlFunctions.GetSelectedData(queryTeamDetail);
        ddlWinningTeam.DataTextField = "TeamName";
        //ddlWinningTeam.DataValueField = "TeamId";
        ddlWinningTeam.DataBind();
      }

    }

当您再次单击按钮页面时，会再次回发，这将导致再次绑定下拉列表。因此，您将获得选定的值作为下拉列表的第一个索引..

【讨论】：