选择下拉列表的初始值

本文关键字：下拉列表 选择 | 更新日期: 2023-09-27 18:16:03

我正试图使下拉列表我已经创建了一个formview的编辑页面内开始的值以前从sql数据库为当前用户选择。

到目前为止，我已经有了正确填充下拉列表的代码: 
protected void ddlSelect_Init(object sender, EventArgs e)
{
    SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["ReinstatementCS"].ConnectionString);
    SqlCommand myCommand = new SqlCommand("SELECT Prefix, Number, ClassSection, Location, StartTime, EndTime, ClassDay, Prefix + Number  + ', Section: ' + CAST(ClassSection AS VarChar) +  ', Location: ' + Location + ', Start Time: ' + StartTime + ', End Time: ' + EndTime + ', Days: ' + ClassDay + ', Credits: ' + CAST(ClassCredit AS VarChar) AS PN, Capacity, GPAReqAbove1, GPAReqBelow1, CreditReqAbove30, CreditReqBelow30, ClassCredit, IsTransfer, SLN FROM Classes");
    myCommand.Connection = con;
    SqlDataAdapter da = new SqlDataAdapter(myCommand);
    DataTable dt = new DataTable();
    da.Fill(dt);
    DropDownList ddlSelect = FVStudentClass.FindControl("ddlSelect") as DropDownList;
    ddlSelect.DataSource = dt;
    ddlSelect.DataTextField = "PN";
    ddlSelect.DataValueField = "SLN";
    ddlSelect.DataBind();
    con.Close();
}

其中SLN为下拉列表中每一项的唯一值，PN为下拉列表中每一项的背景信息。我希望突出显示的项目是对应于特定用户已经存储在数据库中的PN。问题是，当我尝试选择该值时，我使用:

 protected void FVStudentClass_ModeChanging(object sender, FormViewCommandEventArgs e)
    {
        if (FVStudentClass.CurrentMode != FormViewMode.Edit)
            return;
        SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["ReinstatementCS"].ConnectionString);
        SqlCommand myCommand = new SqlCommand("SELECT Prefix + Number  + ', Section: ' + CAST(ClassSection AS VarChar) +  ', Location: ' + Location + ', Start Time: ' + StartTime + ', End Time: ' + EndTime + ', Days: ' + ClassDay + ', Credits: ' + CAST(ClassCredit AS VarChar) AS PN, SLN FROM Classes JOIN StudentClass on SLN = SCClass WHERE SCWSUID = " + Request.QueryString["ALWSUID"]);
        myCommand.Connection = con;
        SqlDataAdapter da = new SqlDataAdapter(myCommand);
        DataTable dt = new DataTable();
        da.Fill(dt);
        DropDownList ddlSelect = new DropDownList();
        ddlSelect = FVStudentClass.FindControl("ddlSelect") as DropDownList;
        if (ddlSelect != null)
        {
            ddlSelect.DataSource = dt;
            ddlSelect.Items.FindByText(dt.Rows[0]["PN"].ToString()).Selected = true;
        }
        con.Close();
    }

，但我仍然卡住了，因为下拉列表不开始与保存的值被选中。你知道怎么解决吗?我是否使用了错误的命令(我应该使用除了ModeChanging之外的东西吗)?谢谢!

选择下拉列表的初始值

尝试实现在FormView DataBound事件上选择DropDownList项的逻辑，ModeChanging事件发生在模式实际改变之前

您应该能够直接设置ddlSelect。SelectedValue为您希望下拉菜单选择的值。

ddlSelect.SelectedValue = dt.Rows[0]["PN"].ToString();
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