C# 一年范围内有2个下拉列表_C#_Asp.net_Webforms_Viewstate

C# 一年范围内有2个下拉列表

c# asp.net

C# 一年范围内有2个下拉列表,c#,asp.net,webforms,viewstate,C#,Asp.net,Webforms,Viewstate,我被困在一个我真的没想到会被耽搁这么多小时的问题上，这让我发疯如标题所述，我需要两个下拉列表，其中ToYears列表的值从FromYear开始： FromYear 2000年 2001年 2002年 2003年 2004年今年 2002年 2003年 2004年因此，我尝试在FromYear的SelectedIndex事件期间使用2并更改selected ToYear，但这会触发selected FromYear事件，不知何故它不会再次触发现在我从Ajax控件工具包中找到了，并认为这可能

我被困在一个我真的没想到会被耽搁这么多小时的问题上，这让我发疯

如标题所述，我需要两个下拉列表，其中ToYears列表的值从FromYear开始：

FromYear
2000年
2001年
2002年
2003年
2004年

今年
2002年
2003年
2004年

因此，我尝试在FromYear的SelectedIndex事件期间使用2并更改selected ToYear，但这会触发selected FromYear事件，不知何故它不会再次触发

现在我从Ajax控件工具包中找到了，并认为这可能是一件好事。但我不想调用web服务，而是希望在实际页面后面的代码中使用方法

此外，回发后应记住所选内容，并且年份范围根据代码隐藏中的属性而变化

我在某个地方读到autopostback不能与CascadingDropDown一起工作

您认为最优雅、最简单的解决方案是什么

事先非常感谢

编辑：我将发布我文章的几个部分-希望能有所帮助标记：

填充

DropDownList

控件听起来很简单，对吗？当您使用ASP.NET WebForms的默认行为时。但是，当您想要获得特定功能时，可能会遇到一些问题，例如，在WebForms中，尝试使用AJAX填充

DropDownLists

（这是一个真正的难题，我找到的唯一解决方案是禁用页面

上的安全检查。最后，我找到了解决方案，我认为这是一个不错的解决方案，因为它使我能够：

首先用数据填充两个DDL
在两个DDL中预选项目
仍然在页面上使用EnableEventValidation=“true”
我只需在DDL上调用DataBind（）；即可更新DDL

与我以前的方法的主要区别是，我在DDL的OnDataBinding事件期间使用数据填充DDL。因此，当我在PageLoad期间执行DataBind（）时，这将自动发生。我首先必须确保的唯一一件事是填充包含我的信息的字典
如果我想从FromYearsDDL的SelectionChange事件中更新ToYearsDDL，我只需更新ToYearsDDL的数据并调用ToYearsDDL.DataBind（）
希望这能帮助其他遇到同样问题的人
下面是标记：
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="LinkedDropDownsBound.aspx.cs"
    Inherits="ASP.Net_Spielwiese.LinkedDropDownsBound"  EnableEventValidation="true" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <asp:ScriptManager ID="ScriptManager1" runat="server">
    </asp:ScriptManager>
    <div>
        <asp:UpdatePanel runat="server" ID="updatePanel">
            <ContentTemplate>
                <div>
                    <asp:Label ID="FromLabel" Text="From" Enabled="false" runat="server"  />
                </div>
                <div>
                    <asp:DropDownList runat="server" ID="FromYearsDDL" AutoPostBack="true" CausesValidation="false" OnDataBinding="DDLFromDataBind"
                        OnSelectedIndexChanged="DDLFromSelectedIndexChanged">
                    </asp:DropDownList>
                </div>
                <div>
                    <asp:Label ID="ToLabel" Text="To" Enabled="false" runat="server" />
                </div>
                <div>
                    <asp:DropDownList runat="server" ID="ToYearsDDL" AutoPostBack="true" CausesValidation="false" OnDataBinding="DDLToDataBind"
                        OnSelectedIndexChanged="DDLToSelectedIndexChanged"/>
                </div>
            </ContentTemplate>
        </asp:UpdatePanel>
    </div>
    </form>
</body>
</html>



下面是代码：
public partial class LinkedDropDownsBound : System.Web.UI.Page
{
    public Dictionary<String, Boolean> FromYears
    {
        get
        {
            if (ViewState["FromYears"] == null)
            {
                ViewState["FromYears"] = new Dictionary<String, Boolean>();
            }
            return ViewState["FromYears"] as Dictionary<String, Boolean>;
        }
        set
        {
            ViewState["FromYears"] = value;
        }
    }
    public Dictionary<String, Boolean> ToYears
    {
        get
        {
            if (ViewState["ToYears"] == null)
            {
                ViewState["ToYears"] = new Dictionary<String, Boolean>();
            }
            return ViewState["ToYears"] as Dictionary<String, Boolean>;
        }
        set
        {
            ViewState["ToYears"] = value;
        }
    }

    public int MinYear = 1975;
    public int MaxYear = 2015;


    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            InitFromYears();
            InitToYears();
            DataBind();
        }
    }

    private void InitFromYears()
    {
        FromYears = new Dictionary<string, bool>();
        IEnumerable<int> fromRange = Enumerable.Range(MinYear, MaxYear - MinYear);

        foreach (var fromYear in fromRange)
        {
            FromYears.Add(fromYear.ToString(), fromYear == (DateTime.Now.Year - 2));
        }
    }

    private void InitToYears()
    {
        ToYears = new Dictionary<string, bool>();
        //get the selected FromYear Value
        int minToYear = Convert.ToInt32(FromYears.FirstOrDefault(dict => dict.Value).Key);
        //make sure ToYears is at least FromYears
        if (minToYear < Convert.ToInt32(FromYears.Min(k => k.Key)))
        {
            minToYear = Convert.ToInt32(FromYears.Min(k => k.Key));
        }
        IEnumerable<int> toRange = Enumerable.Range(minToYear, MaxYear - minToYear);
        foreach (var toYear in toRange)
        {
            ToYears.Add(toYear.ToString(), toYear == (DateTime.Now.Year + 2));
        }
    }

    protected void DDLFromDataBind(object sender, EventArgs e)
    {
        FromYearsDDL.DataSource = FromYears;
        FromYearsDDL.DataValueField = "Key";
        FromYearsDDL.DataTextField = "Key";
        FromYearsDDL.SelectedValue = FromYears.FirstOrDefault(y => y.Value).Key;
    }

    protected void DDLFromSelectedIndexChanged(object sender, EventArgs e)
    {
        //update the FromYear Dictionary
        var tempDictionary = FromYears.ToDictionary(fromYear => fromYear.Key, fromYear => fromYear.Key.Equals(FromYearsDDL.SelectedValue));
        FromYears = tempDictionary;

        //Call Bind on the ToYear DDL
        ToYearsDDL.DataBind();

        //do my other update stuff here
        FromLabel.Text = FromYearsDDL.SelectedValue;
        ToLabel.Text = ToYearsDDL.SelectedValue;
    }

    protected void DDLToSelectedIndexChanged(object sender, EventArgs e)
    {
        //do my other update stuff here
        FromLabel.Text = FromYearsDDL.SelectedValue;
        ToLabel.Text = ToYearsDDL.SelectedValue;
    }

    protected void DDLToDataBind(object sender, EventArgs e)
    {
        InitToYears();
        ToYearsDDL.DataSource = ToYears;
        ToYearsDDL.DataValueField = "Key";
        ToYearsDDL.DataTextField = "Key";
        ToYearsDDL.SelectedValue = ToYears.FirstOrDefault(y => y.Value).Key;
    }
}

public分部类LinkedDropDownsBound:System.Web.UI.Page
{
年公共词典
{
得到
{
如果（ViewState[“FromYears”]==null）
{
ViewState[“FromYears”]=新字典（）；
}
将ViewState[“FromYears”]作为字典返回；
}
设置
{
ViewState[“FromYears”]=值；
}
}
公共词典
{
得到
{
如果（ViewState[“ToYears”]==null）
{
ViewState[“ToYears”]=新字典（）；
}
将ViewState[“ToYears”]作为字典返回；
}
设置
{
ViewState[“ToYears”]=值；
}
}
公共财政年度=1975年；
公共int MaxYear=2015年；
受保护的无效页面加载（对象发送方、事件参数e）
{
如果（！IsPostBack）
{
初始年（）；
初始年份（）；
数据绑定（）；
}
}
私人股本年数（）
{
FromYears=新字典（）；
IEnumerable fromRange=Enumerable.Range（MinYear，MaxYear-MinYear）；
foreach（fromRange中的var fromYear）
{
FromYears.Add（fromYear.ToString（），fromYear==（DateTime.Now.Year-2））；
}
}
私人股本年数（）
{
ToYears=新字典（）；
//获取所选的FromYear值
int minToYear=Convert.ToInt32（从years.FirstOrDefault（dict=>dict.Value.Key）；
//确保ToYears至少是FromYears
if（minToYeark.Key）））
{
minToYear=Convert.ToInt32（FromYears.Min（k=>k.Key））；
}
IEnumerable toRange=可枚举的.Range（minToYear，MaxYear-minToYear）；
foreach（toRange的当年var）
{
添加（toYear.ToString（），toYear==（DateTime.Now.Year+2））；
}
}
受保护的void DDLFromDataBind（对象发送方，事件参数e）
{
fromYearsdl.DataSource=FromYears；
fromYearsdl.DataValueField=“Key”；
fromYearsdl.DataTextField=“Key”；
FromYearsdl.SelectedValue=FromYears.FirstOrDefault（y=>y.Value）.Key；
}
受保护的无效DDLFromSelectedIndexChanged（对象发送方，事件参数e）
{
//更新FromYear字典
var tempDictionary=FromYears.ToDictionary（fromYear=>fromYear.Key，fromYear=>fromYear.Key.Equals（FromYearsDDL.SelectedValue））；
FromYears=临时字典；
//调用ToYear DDL上的Bind
toyersddl.DataBind（）；
//在这里做我的其他更新
FromLabel.Text=fromYearsdl.SelectedValue；
ToLabel.Text=ToYearsDDL.SelectedValue；
}
受保护的无效DDLToSelectedIndexChanged（对象发送方，事件参数e）
{
//在这里做我的其他更新
FromLabel.Text=fromYearsdl.SelectedValue；
ToLabel.Text=ToYearsDDL.SelectedValue；
}
受保护的void DDLToDataBind（对象发送方，事件参数e）
{
初始年份（）；
ToYearsDDL.DataSource=ToYears；
    protected void FromYearChanged(object sender, EventArgs e)
    {
        SelectedFromYear = int.Parse(DropDownToYear.SelectedValue);
        SelectedToYear = int.Parse(DropDownFromYear.SelectedValue);
        if (SelectedFromYear > SelectedToYear)
        {
            SelectedToYear = SelectedFromYear;
        }
        UpdateGanttTables();
    }

    protected void ToYearChanged(object sender, EventArgs e)
    {
        SelectedFromYear = int.Parse(DropDownToYear.SelectedValue);
        SelectedToYear = int.Parse(DropDownFromYear.SelectedValue);
        UpdateGanttTables();
    }

    <asp:ScriptManager runat="server" ID="sm" />
    <asp:UpdateProgress runat="server" AssociatedUpdatePanelID="updatePanel" DisplayAfter="0" DynamicLayout="true">
        <ProgressTemplate>
            Working...
        </ProgressTemplate>
    </asp:UpdateProgress>
    <asp:UpdatePanel runat="server" ID="updatePanel">
        <ContentTemplate>
            <div>
                <asp:Label ID="Label1" Text="From" runat="server" AssociatedControlID="from" />
            </div>
            <div>
                <asp:DropDownList runat="server" ID="from" AutoPostBack="true" CausesValidation="false" OnSelectedIndexChanged="from_SelectedIndexChanged">
                </asp:DropDownList>
            </div>
            <div>
                <asp:Label ID="Label2" Text="To" runat="server" AssociatedControlID="to" />
            </div>
            <div>
                <asp:DropDownList runat="server" ID="to" />
            </div>
        </ContentTemplate>
    </asp:UpdatePanel>

    private const int MaxYear = 2030;
    private const int MinYear = 1959;

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!this.IsPostBack)
        {
            var fromRange = Enumerable.Range(MinYear, MaxYear - MinYear);

            this.from.DataSource = fromRange;
            this.from.DataBind();
        }
    }

    protected void from_SelectedIndexChanged(object sender, EventArgs e)
    {
        var selectedYear = Convert.ToInt32(this.from.SelectedValue);
        var toRange = Enumerable.Range(selectedYear, MaxYear - selectedYear);

        this.to.DataSource = toRange;
        this.to.DataBind();
    }

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="LinkedDropDownsBound.aspx.cs"
    Inherits="ASP.Net_Spielwiese.LinkedDropDownsBound"  EnableEventValidation="true" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <asp:ScriptManager ID="ScriptManager1" runat="server">
    </asp:ScriptManager>
    <div>
        <asp:UpdatePanel runat="server" ID="updatePanel">
            <ContentTemplate>
                <div>
                    <asp:Label ID="FromLabel" Text="From" Enabled="false" runat="server"  />
                </div>
                <div>
                    <asp:DropDownList runat="server" ID="FromYearsDDL" AutoPostBack="true" CausesValidation="false" OnDataBinding="DDLFromDataBind"
                        OnSelectedIndexChanged="DDLFromSelectedIndexChanged">
                    </asp:DropDownList>
                </div>
                <div>
                    <asp:Label ID="ToLabel" Text="To" Enabled="false" runat="server" />
                </div>
                <div>
                    <asp:DropDownList runat="server" ID="ToYearsDDL" AutoPostBack="true" CausesValidation="false" OnDataBinding="DDLToDataBind"
                        OnSelectedIndexChanged="DDLToSelectedIndexChanged"/>
                </div>
            </ContentTemplate>
        </asp:UpdatePanel>
    </div>
    </form>
</body>
</html>

public partial class LinkedDropDownsBound : System.Web.UI.Page
{
    public Dictionary<String, Boolean> FromYears
    {
        get
        {
            if (ViewState["FromYears"] == null)
            {
                ViewState["FromYears"] = new Dictionary<String, Boolean>();
            }
            return ViewState["FromYears"] as Dictionary<String, Boolean>;
        }
        set
        {
            ViewState["FromYears"] = value;
        }
    }
    public Dictionary<String, Boolean> ToYears
    {
        get
        {
            if (ViewState["ToYears"] == null)
            {
                ViewState["ToYears"] = new Dictionary<String, Boolean>();
            }
            return ViewState["ToYears"] as Dictionary<String, Boolean>;
        }
        set
        {
            ViewState["ToYears"] = value;
        }
    }

    public int MinYear = 1975;
    public int MaxYear = 2015;


    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            InitFromYears();
            InitToYears();
            DataBind();
        }
    }

    private void InitFromYears()
    {
        FromYears = new Dictionary<string, bool>();
        IEnumerable<int> fromRange = Enumerable.Range(MinYear, MaxYear - MinYear);

        foreach (var fromYear in fromRange)
        {
            FromYears.Add(fromYear.ToString(), fromYear == (DateTime.Now.Year - 2));
        }
    }

    private void InitToYears()
    {
        ToYears = new Dictionary<string, bool>();
        //get the selected FromYear Value
        int minToYear = Convert.ToInt32(FromYears.FirstOrDefault(dict => dict.Value).Key);
        //make sure ToYears is at least FromYears
        if (minToYear < Convert.ToInt32(FromYears.Min(k => k.Key)))
        {
            minToYear = Convert.ToInt32(FromYears.Min(k => k.Key));
        }
        IEnumerable<int> toRange = Enumerable.Range(minToYear, MaxYear - minToYear);
        foreach (var toYear in toRange)
        {
            ToYears.Add(toYear.ToString(), toYear == (DateTime.Now.Year + 2));
        }
    }

    protected void DDLFromDataBind(object sender, EventArgs e)
    {
        FromYearsDDL.DataSource = FromYears;
        FromYearsDDL.DataValueField = "Key";
        FromYearsDDL.DataTextField = "Key";
        FromYearsDDL.SelectedValue = FromYears.FirstOrDefault(y => y.Value).Key;
    }

    protected void DDLFromSelectedIndexChanged(object sender, EventArgs e)
    {
        //update the FromYear Dictionary
        var tempDictionary = FromYears.ToDictionary(fromYear => fromYear.Key, fromYear => fromYear.Key.Equals(FromYearsDDL.SelectedValue));
        FromYears = tempDictionary;

        //Call Bind on the ToYear DDL
        ToYearsDDL.DataBind();

        //do my other update stuff here
        FromLabel.Text = FromYearsDDL.SelectedValue;
        ToLabel.Text = ToYearsDDL.SelectedValue;
    }

    protected void DDLToSelectedIndexChanged(object sender, EventArgs e)
    {
        //do my other update stuff here
        FromLabel.Text = FromYearsDDL.SelectedValue;
        ToLabel.Text = ToYearsDDL.SelectedValue;
    }

    protected void DDLToDataBind(object sender, EventArgs e)
    {
        InitToYears();
        ToYearsDDL.DataSource = ToYears;
        ToYearsDDL.DataValueField = "Key";
        ToYearsDDL.DataTextField = "Key";
        ToYearsDDL.SelectedValue = ToYears.FirstOrDefault(y => y.Value).Key;
    }
}

private void BindYearDropdown()
        {
            int year;

            for (year = DateTime.Now.Year; year >= 2010 ; year--)
            {
                DDLYear.Items.Add(year.ToString());
            }
        }