检查是否有对ListBox控件选择

在前网页前端处，我们放置ListBox控件，在数据提交前，检查用户是否有对此控件进行选择？ Insus.NET的方法是使用Javascript与CustomValidator自定义验证控件来检查。

可以看到最终结果：

 

你也想参此例子，可以参考下面数据与准备方法，写一个对象，它将用来产生十个天干。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

/// <summary>
/// Summary description for HeavenlyStem
/// </summary>
public class HeavenlyStem
{
    private int _ID;
    private string _Name;

    public int ID
    {
        get { return _ID; }
        set { _ID = value; }
    }

    public string Name
    {
        get { return _Name; }
        set { _Name = value; }
    }

    public HeavenlyStem()
    {
        //
        // TODO: Add constructor logic here
        //
    }

     public HeavenlyStem(int id, string name)
        {
            this.ID = id;
            this._Name = name;
        }
}

产生与用泛型来存储它们：

 private List<HeavenlyStem> GetHeavenStem()
    {
        List<HeavenlyStem> ListHS = new List<HeavenlyStem>();
        HeavenlyStem hs = new HeavenlyStem();
        hs.ID = 1;
        hs.Name = "甲";
        ListHS.Add(hs);

        hs = new HeavenlyStem();
        hs.ID = 2;
        hs.Name = "乙";
        ListHS.Add(hs);

        hs = new HeavenlyStem();
        hs.ID = 3;
        hs.Name = "丙";
        ListHS.Add(hs);

        hs = new HeavenlyStem();
        hs.ID = 4;
        hs.Name = "丁";
        ListHS.Add(hs);

        hs = new HeavenlyStem();
        hs.ID = 5;
        hs.Name = "戊";
        ListHS.Add(hs);

        hs = new HeavenlyStem();
        hs.ID = 6;
        hs.Name = "己";
        ListHS.Add(hs);

        hs = new HeavenlyStem();
        hs.ID = 7;
        hs.Name = "庚";
        ListHS.Add(hs);

        hs = new HeavenlyStem();
        hs.ID = 8;
        hs.Name = "辛";
        ListHS.Add(hs);

        hs = new HeavenlyStem();
        hs.ID = 9;
        hs.Name = "壬";
        ListHS.Add(hs);

        hs = new HeavenlyStem();
        hs.ID = 10;
        hs.Name = "癸";
        ListHS.Add(hs);

        return ListHS;
    }

Html标记：

<asp:ListBox ID="ListBoxHeavenlyStem" runat="server" Width="60" Height="160" SelectionMode="Multiple"></asp:ListBox>
            <asp:CustomValidator ID="CustomValidator1" runat="server" Display="None" ErrorMessage="必须选择选项" ClientValidationFunction="ValidateListBox"></asp:CustomValidator>

            <asp:ValidationSummary ID="ValidationSummary1" runat="server" EnableClientScript="true"
                ShowMessageBox="true" ShowSummary="false" />
            <asp:Button ID="Button1" runat="server" Text="Submit" />

接下来，你需要在.aspx.cs为ListBox控件绑定数据，数据源即是刚才产生的List<HeavenlyStem>：

using System.Collections.Generic;
using System.Data;
using System.Data.OleDb;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using Insus.NET;

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

    private void Data_Binding()
    {
        this.ListBoxHeavenlyStem.DataSource = GetHeavenStem();
        this.ListBoxHeavenlyStem.DataTextField = "Name";
        this.ListBoxHeavenlyStem.DataValueField = "ID";
        this.ListBoxHeavenlyStem.DataBind();
    }   
}

最后是写Javascript脚本：

function ValidateListBox(sender, args) {
            var lb = document.getElementById("<%=ListBoxHeavenlyStem.ClientID%>")
            var options = lb.options;

            args.IsValid = false;

            for (var i = 0; i < options.length; i++) {
                if (options[i].selected == true) {
                    args.IsValid = true;
                    return;
                }
            }
        }