![](/img/trans.png)
[英]An optional parameter must be a reference type, a nullable type, or be declared as an optional
[英]Getting Error An optional parameter must be a reference type, a nullable type, or be declared as an optional parameter
將數據更新到數據庫后出現錯誤
參數字典在'HCIBE.Controllers.ChainsController'中為方法'System.Web.Mvc.ActionResult UpdateChain(Int32,HCIBE.Models.chain)'的非空類型'System.Int32'的參數'id'包含空條目”。 可選參數必須是引用類型,可為空的類型,或者必須聲明為可選參數。
這是我的控制器
[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);
}
視圖
@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>
通過下拉選擇,我填寫所有文本框,當我提交表單時,我得到了錯誤。
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 }
);
}
模型
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; }
}
您正在傳遞chain
的object
,但未在任何地方添加id
值。 您需要設置id
value
並將其添加到chain object
。
提交表單時,您的ID為null,這就是您收到此錯誤的原因。
如您在get方法中所做的那樣,將id參數指定為可為空,或者
將ID存儲在一個隱藏字段中,以將其自動傳遞給像這樣的模型
@HTML.HiddenFor(Model.id)
或手動通過
@HTML.Hidden("id",id)
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