ASP.NET MVC Post请求下如何绑定表单字段到嵌套模型

问题背景 #

使用ASP.NET MVC+MediatR实现CQRS模式，表单提交后，UpdateApplicationCommand中嵌套的ApplicationEditGeneralViewModel字段值始终为null。需要保留嵌套结构以复用ApplicationEditGeneralViewModel，不希望将字段直接移至UpdateApplicationCommand类。

核心原因 #

当前视图的模型是ApplicationEditGeneralViewModel，表单生成的input元素name属性为Name、Description，但控制器接收的是UpdateApplicationCommand，其嵌套属性路径为ApplicationEditGeneralViewModel.Name，ASP.NET MVC的模型绑定无法自动匹配这种结构差异，导致嵌套对象为null。

简便解决方案 #

方案一：修改视图模型为UpdateApplicationCommand #

直接将视图的模型改为UpdateApplicationCommand，表单中使用嵌套路径绑定字段，生成的name属性会自动匹配模型绑定要求：

@model UpdateApplicationCommand

<form method="post" asp-action="Edit" asp-controller="Applications">
    <div class="form-floating mb-3">
        @Html.TextBoxFor(m => m.ApplicationEditGeneralViewModel.Name, new { @class = "form-control", placeholder = "Application Name"})
        <label for="ApplicationEditGeneralViewModel_Name">Application Name</label>
    </div>
    <div class="form-floating mb-3">
        @Html.TextBoxFor(m => m.ApplicationEditGeneralViewModel.Description, new { @class = "form-control", placeholder = "Application Description"})
        <label for="ApplicationEditGeneralViewModel_Description">Application Description</label>
    </div>
    <div class="d-flex flex-row-reverse bd-highlight">
        <input type="submit" value="Submit" class="btn btn-primary mt-2" />
    </div>
</form>

方案二：保留原视图模型，手动指定input的name属性 #

如果需要继续使用ApplicationEditGeneralViewModel作为视图模型，只需在TextBoxFor的html属性中手动指定符合嵌套结构的name值：

@model ApplicationEditGeneralViewModel

<form method="post" asp-action="Edit" asp-controller="Applications">
    <div class="form-floating mb-3">
        @Html.TextBoxFor(m => m.Name, new { @class = "form-control", placeholder = "Application Name", name = "ApplicationEditGeneralViewModel.Name"})
        <label for="Name">Application Name</label>
    </div>
    <div class="form-floating mb-3">
        @Html.TextBoxFor(m => m.Description, new { @class = "form-control", placeholder = "Application Description", name = "ApplicationEditGeneralViewModel.Description"})
        <label for="Description">Application Description</label>
    </div>
    <div class="d-flex flex-row-reverse bd-highlight">
        <input type="submit" value="Submit" class="btn btn-primary mt-2" />
    </div>
</form>

验证效果 #

修改后提交表单，ASP.NET MVC的模型绑定会自动将表单值映射到UpdateApplicationCommand.ApplicationEditGeneralViewModel的对应字段中，无需拆分嵌套结构或添加额外路由配置。

内容的提问来源于stack exchange，提问作者Brian Chambers