Getting Error可选参数必须是引用类型、可为null的类型，或者声明为可选参数

本文关键字：参数 类型 或者 null 声明 引用类型 Error Getting 可为 | 更新日期: 2023-09-27 18:25:58

将数据更新到数据库后出错

参数字典包含"HCIBE.Controllers.ChainsController"中方法"System.Web.Mvc.ActionResult UpdateChain（Int32，HCIBE.Models.chain）"的不可为null类型"System.Int32"的参数"id"的null条目。可选参数必须是引用类型、可为null的类型，或者声明为可选参数

这是我的控制器

    [HttpGet]
    public ActionResult UpdateChain(int? id)
    {
        chain objchain = db.chains.Find(id);
        if (objchain == null)
        {
            return HttpNotFound();
        }
        return View(objchain);
    }
    [HttpPost]
    public ActionResult UpdateChain(int id, [Bind(Include = "name,code,username,password,updated_by,updated_on")] chain chain)
    {
        chain _objchain = db.chains.Find(id);
        try
        {
        if(ModelState.IsValid)
        {
            _objchain.code = chain.code;
            _objchain.name = chain.name;
            _objchain.username = chain.username;
            _objchain.password = chain.password;
            _objchain.updated_by = Convert.ToInt32("1");
            _objchain.updated_on = DateTime.Now;
            db.Entry(_objchain).State = EntityState.Modified;
            db.SaveChanges();
            return RedirectToAction("Index");
        }
        }
        catch (Exception Ex)
        {
            ModelState.AddModelError("", "Unable to update data");
        }
        return View(_objchain);
    }

查看

@using (@Html.BeginForm("UpdateChain", "Chains", FormMethod.Post))
{
<div class="form-horizontal">
    <hr />
    <div class="form-group">
        <label class="col-sm-2 control-label">
            Select Chain
        </label>
        <div class="col-md-3">
            @Html.DropDownList("ddlchainname", (SelectList)ViewData["chain_name"],"Select Chain", new { onchange = "Action(this.value);", @class = "form-control" })
        </div>
        <label class="control-label">
            or @Html.ActionLink("Add New", "Create")
        </label>
    </div>
    <div class="form-group">
        <label class="col-sm-2 control-label">
            Chain Name
        </label>
        <div class="col-md-3">
            @Html.TextBox("ChainName", null, new { @class = "form-control" })
        </div>
        <label class="col-sm-2 control-label">
            Username
        </label>
        <div class="col-md-3">
            @Html.TextBox("username", null, new { @class = "form-control" })
        </div>
    </div>
    <div class="form-group">
        <label class="col-sm-2 control-label">
            Chain Code
        </label>
        <div class="col-md-3">
            @Html.TextBox("ChainCode", null, new { @class = "form-control" })
        </div>
        <label class="col-sm-2 control-label">
            Password
        </label>
        <div class="col-md-3">
            @Html.Password("password", null, new { @class = "form-control" })
        </div>
    </div>
    <div class="form-group">
        <div class="col-md-offset-2 col-md-10">
            <input type="submit" value="Update" onclick="UpdateChain()" class="btn btn-default" />
        </div>
    </div>
</div>
}
<script type="text/javascript">
    function UpdateChain(){
        var _vddlChainID = $("#ddlchainname").val();
        alert("Your Selected ID = " + _vddlChainID);
        $.ajax({
            url: '@Url.Action("UpdateChain", "Chains")',
            type: "POST",
            data: { "id": _vddlChainID }
        });
    }
</script>

通过下拉选择我填写所有文本框，当我提交表格时，我会得到错误。

路由

    public static void RegisterRoutes(RouteCollection routes)
    {
        routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
        routes.MapRoute(
            name: "Default",
            url: "{controller}/{action}/{id}",
            defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }
        );
    }

型号

public partial class chain
{
    public chain()
    {
        this.templates = new HashSet<template>();
        this.hotels = new HashSet<hotel>();
    }
    public long chain_id { get; set; }
    public string name { get; set; }
    public string code { get; set; }
    public string username { get; set; }
    public string password { get; set; }
    public long created_by { get; set; }
    public System.DateTime created_on { get; set; }
    public Nullable<long> updated_by { get; set; }
    public Nullable<System.DateTime> updated_on { get; set; }
    public virtual ICollection<template> templates { get; set; }
    public virtual ICollection<hotel> hotels { get; set; }
}

Getting Error可选参数必须是引用类型、可为null的类型，或者声明为可选参数

您正在传递chain的object，但在任何位置都没有添加id的值。您需要设置id的value，并将其添加到chain object中。

提交表单时，您的id为null，这就是您出现此错误的原因。

指定id参数可以为null，就像在get方法或中所做的那样

将id存储在一个隐藏字段中，以便使用类似的模型自动传递

@HTML.HiddenFor(Model.id)

或手动通过

@HTML.Hidden("id",id)
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