在发布请求期间，绑定模型为null

Question

我在asp.net核心中存在模型绑定问题。我有一个模型，其中包含属性和另一个模型的列表。当我提交要显示的模型时，它可以正常工作。我使用调试器跟踪值，并且当我通过表单提交执行发布请求时，剃刀视图中的模型变为空。请帮助我。

我目前正在使用Asp.net core 2.2 MVC，并且正在使用asp-for标记将form属性链接到模型。

<div class="row">
<form asp-action="Edit" method="post">
    <div asp-validation-summary="ModelOnly" class="text-danger"></div>
    <input hidden asp-for="@Model.UserId" />
    <div class="col-sm-5 col-md-4 col-lg-4 col-xl-4">
        <div class="form-group">
            <label asp-for=@Model.Username></label>
            <input readonly asp-for=@Model.Username class="form-control" />
            <span asp-validation-for=@Model.Username class="text-danger"></span>
        </div>

        <div class="form-group">
            <label asp-for=@Model.Name></label>
            <input readonly asp-for=@Model.Name class="form-control" />
            <span asp-validation-for=@Model.Name class="text-danger"></span>
        </div>

        <div class="form-group">
            <label asp-for=@Model.Email></label>
            <input readonly asp-for=@Model.Email class="form-control" />
            <span asp-validation-for=@Model.Email class="text-danger"></span>
        </div>
    </div>
    <div class="row ml-1 form-group">
        <div class="col-sm-2 col-md-2 col-lg-2">
            Template
        </div>
        <div class="col-sm-2 col-md-2 col-lg-2">
            Entity
        </div>
        <div class="col-sm-8 col-md-8 col-lg-8 ">
            Role Assigned
        </div>
        @for (int i= 0; i < Model.EntityUserList.Count(); i++)
        {
            <input hidden asp-for="@Model.EntityUserList[i].TemplateId" />
            <div class="my-2 col-sm-2 col-md-2 col-lg-2">
                @Model.EntityUserList[i].TemplateName
            </div>

            <input hidden asp-for="@Model.EntityUserList[i].EntityId" />
            <div class="my-2 col-sm-2 col-md-2 col-lg-2">
                @Model.EntityUserList[i].EntityTitle
            </div>
            <div class="col-sm-8 col-md-8 col-lg-8 row ml-1">
                <div class="custom-control custom-checkbox my-2 col-sm-2 col-md-2 col-lg-2">
                    <input type="checkbox" class="custom-control-input" asp-for="@Model.EntityUserList[i].IsSubmitter">
                    <label class="custom-control-label" asp-for="@Model.EntityUserList[i].IsSubmitter">
                        Submitter
                    </label>
                </div>

                <div class="custom-control custom-checkbox my-2 col-sm-2 col-md-2 col-lg-2">
                    <input type="checkbox" class="custom-control-input" asp-for="@Model.EntityUserList[i].IsApprover">
                    <label class="custom-control-label" asp-for="@Model.EntityUserList[i].IsApprover">
                        Approver
                    </label>
                </div>

                <div class="custom-control custom-checkbox my-2 col-sm-2 col-md-2 col-lg-2">
                    <input type="checkbox" class="custom-control-input" asp-for="@Model.EntityUserList[i].IsAdmin">
                    <label class="custom-control-label" asp-for="@Model.EntityUserList[i].IsAdmin">
                        Admin
                    </label>
                </div>
            </div>

        }
    </div>




    <div class="form-group mt-3 ml-3">
        <input type="submit" value="Update" class="btn btn-outline-primary mr-3" />
        <a asp-controller="UserManagement" asp-action="Index" class="btn btn-outline-info" style="width:auto">
            Cancel
        </a>
    </div>
</form>

当我执行post方法时，模型会抛出一个空引用异常。