可空布尔值列表始终归零 [英] list of nullable bool values is always nulls

问题描述

我有一个局部视图。在我的部分的一些属性是可空布尔值。如果我选中或清除该复选框它总是空当我保存了这个纪录。我应该怎么做，如果我希望它返回false时检查取消和真正取消选中时检查，否则空？

下面是实体类：

 公共字符串描述{搞定;组; }
    [需要]
    公共字符串的DocType {搞定;组; }
    [显示（名称=用户）]
    [需要]
    公众诠释键{搞定;组; }
    [显示（NAME =路径）
    公共字符串名称{;组; }
    公共BOOL？ ShowFullWidth {搞定;组; }
    公开名单＆LT; D​​mFormDefDTO＆GT; DmFormDefItems {搞定;组; }
    公共BOOL？ IsEnabled {搞定;组; }
 

下面是我的部分观点：

 如果（Model.DmFormDefItems！= NULL）
        {
＆LT; D​​IV CLASS =主体＆GT;
    ＆LT; D​​IV ID =容器体＆GT;
        ＆LT;表类=表表边框的表格条纹ID =ordertable＆GT;
            ＆LT;＆THEAD GT;
                ＆所述; TR＆GT;                    ＆LT;第i个已启用
                    ＆LT; /第i
                ＆LT; / TR＆GT;
            ＆LT; / THEAD＆GT;
            ＆LT;＆TBODY GT;
                @for（INT I = 0; I＆LT; Model.DmFormDefItems.Count;我++）
                {
                    ＆所述; TR类=OrderDetailRow＆GT;
                        ＆所述; TD＆GT;
                            @if（Model.DmFormDefItems.ElementAt（I）.ShowFullWidth == true）而
                            {
                                @ Html.CheckBoxFor（M = GT; m.DmFormDefItems [I] .ShowFullWidth.HasValue）LT;标签＆gt;查看全宽页＆LT; /标签＆gt;
                            }
                            其他
                            {
                                @ Html.CheckBoxFor（M = GT; m.DmFormDefItems [I] .ShowFullWidth.HasValue）LT;标签＆gt;查看全宽页＆LT; /标签＆gt;
                            }
                        ＆LT; / TD＆GT;
                        ＆所述; TD＆GT;
                            @if（Model.DmFormDefItems.ElementAt（I）.IsEnabled == true）而
                            {
                                @ Html.CheckBoxFor（M = GT; m.DmFormDefItems [I] .IsEnabled.HasValue）
                            }
                            其他
                            {
                                @ Html.CheckBoxFor（M = GT; m.DmFormDefItems [I] .IsEnabled.HasValue）
                            }
                        ＆LT; / TD＆GT;
                    ＆LT; / TR＆GT;
                }
            ＆LT; / TBODY＆GT;
        ＆LT; /表＆gt;
 

解决方案

首先，你不绑定到你的布尔属性，您绑定到这是一个只读属性的的HasValue 属性的可空＆LT; T＆GT; （参考文档），这意味着，当你回来后不能设置，因此在控制器的价值永远是默认的空值。

一个复选框，仅有2个国家（真正或假），但可空＆LT;布尔＆GT; 有3种状态（真正或假或空），所以没有办法一个可空＆LT;布尔方式＆gt; 可重新$使用复选框，输入p $ psented

3可能的选择。

1. 使用 @ Html.EditorFor（M = GT; m.yourNullableBool）这将产生一个
   下拉3的值（真，假和未设置）


2. 使用3单选势必按钮你的可空＆LT;布尔＆GT; 属性与价值
   真正，假和空


3. 发展你自己的HTML帮助和jQuery插件

I have a partial view. In my partial a few properties are nullable boolean. If I check or uncheck the checkbox it is always null when I save the this record. What should I do if I want it to return false when check to uncheck and true when uncheck to check, otherwise null?

Here is the Entity class:

    public string Description { get; set; }
    [Required]
    public string DocType { get; set; }
    [Display(Name = "User")]
    [Required]
    public int Key { get; set; }
    [Display(Name = "Path")]
    public string Name { get; set; }
    public bool? ShowFullWidth { get; set; }
    public List<DmFormDefDTO> DmFormDefItems { get; set; }
    public bool? IsEnabled { get; set; }

Here is my partial view:

  if (Model.DmFormDefItems != null)
        {
<div class="main-body">
    <div id="container-body">
        <table class="table table-bordered table-striped" id="ordertable">
            <thead>
                <tr>

                    <th>Enabled
                    </th>
                </tr>
            </thead>
            <tbody>
                @for (int i = 0; i < Model.DmFormDefItems.Count; i++)
                {
                    <tr class="OrderDetailRow">
                        <td>
                            @if (Model.DmFormDefItems.ElementAt(i).ShowFullWidth == true)
                            {
                                @Html.CheckBoxFor(m => m.DmFormDefItems[i].ShowFullWidth.HasValue) <label>Show Full Width Page</label>    
                            }
                            else
                            {
                                @Html.CheckBoxFor(m => m.DmFormDefItems[i].ShowFullWidth.HasValue) <label>Show Full Width Page</label>                                            
                            }
                        </td>
                        <td>
                            @if (Model.DmFormDefItems.ElementAt(i).IsEnabled == true)
                            {
                                @Html.CheckBoxFor(m => m.DmFormDefItems[i].IsEnabled.HasValue)     
                            }
                            else
                            {
                                @Html.CheckBoxFor(m => m.DmFormDefItems[i].IsEnabled.HasValue)        
                            }
                        </td>
                    </tr>              
                }
            </tbody>
        </table>

解决方案

Firstly you not binding to your boolean property, your binding to its HasValue property which is a readonly property of Nullable<T> (refer documentation) which means it cannot be set when you post back, so the value in your controller will always be the default null value.

A checkbox only has 2 states (true or false) but a Nullable<bool> has 3 states (true or false or null) so there is no way a Nullable<bool> can be represented using a checkbox input.

3 possible options

1. Use @Html.EditorFor(m => m.yourNullableBool) which will generate a dropdown with 3 values ("True", "False" and "Not Set")
2. Use 3 radio buttons bound to your Nullable<bool> property with the values true, false and null
3. Develop you own html helper and jquery plugin

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