在剃刀页面中变量的 OnPost 值重置为 null 之后
after OnPost values of variables reset to null in razor pages
我想在我的页面上添加简单的点赞功能(仅显示数据)。
我的页面后面有 PageModel 中的方法(这只是示例,因为我的页面太复杂了):
(..)getting DB context and stuff
public string bookName {get;set;}
public string someVariable1 {get;set;}
public List<string> _bookTags {get;set;}
public int LikeCounter {get;set;}
public void OnGet(){
someVariable1 = (from u in _context.table
where something==something
select u.x);
_bookTags= (from u in _context.bookTags
where something==something
select u.y).ToList();
LikeCounter = (from u in _context.likes
where u.book==bookName
select u).Count();
}
public void OnPost(){
likes newLike = new likes();
newLike.userName = HttpContext.User.Identity.Name.Split("\")[1];
newLike.book = bookName;
_context.likes.add(newLike);
_context.SaveChanges();
}
页面如下所示:
(..)
<div class="col-lg-4">
<form method="post">
<button class="btn btn-reddit" type="submit">LikeThisBook</button>
</form>
Current likes: @Model.LikeCounter
</div>
(..)
@foreach(string x in Model._bookTags){
<div class="border">
@x
</div>
}
(..)
所以问题是当我显示页面时 - 一切正常,但是当我单击“LikeThisBook”时 - OnPost 方法触发,为这本书添加用户名的喜欢...然后页面显示错误:
ArgumentNullException: Value cannot be null. (Parameter 'source')
并在堆栈跟踪中:
SomeProjectName.Pages.SomeBookStore.Pages_SomeBookStore_ShowBook.ExecuteAsync() in ShowBook.cshtml
@foreach(string x in Model._bookTags){ <- this is colored red
所以看起来在“OnGet”方法中填充的每个变量现在都是空的...
请帮忙:)
如果您不想重新加载页面并希望更新 counter.The,常用方法是使用 ajax。
这是一个工作演示:
Index.cshtml:
@page
@model IndexModel
<div class="col-lg-4">
<form method="post">
<input name="bookName" />
<button type="button" class="btn btn-reddit" onclick="Add()">LikeThisBook</button>
</form>
Current likes: <label>@Model.LikeCounter</label> @*add this*@
</div>
@foreach (string x in Model._bookTags)
{
<div class="border">
@x
</div>
}
@section Scripts
{
<script>
function Add() {
$.ajax({
type: "post",
beforeSend: function (xhr) {
xhr.setRequestHeader("XSRF-TOKEN",
$('input:hidden[name="__RequestVerificationToken"]').val());
},
success: function (data) {
$("label").html(data);
},
error: function () {
alert("Fail to add");
}
});
}
</script>
}
Index.cshtml.cs:
public class IndexModel : PageModel
{
private readonly RazorProj3_1Context _context;
public IndexModel(RazorProj3_1Context context)
{
_context = context;
}
[BindProperty]
public string bookName { get; set; }
public string someVariable1 { get; set; }
public List<string> _bookTags { get; set; }
public int LikeCounter { get; set; }
public void OnGet()
{
someVariable1 = (from u in _context.table
where u.Id == 1
select u.x).FirstOrDefault();
_bookTags = (from u in _context.bookTags
select u.y).ToList();
LikeCounter = (from u in _context.likes
//where u.book == bookName
select u).Count();
}
public ActionResult OnPost()
{
like newLike = new like();
newLike.book = bookName;
_context.likes.Add(newLike);
_context.SaveChanges();
LikeCounter = (from u in _context.likes
//where u.book == bookName
select u).Count();
return new JsonResult(LikeCounter);
}
}
Startup.cs:
services.AddAntiforgery(o => o.HeaderName = "XSRF-TOKEN");
我的测试模型:
public class likes
{
public int Id { get; set; }
public string book { get; set; }
}
public class BookTag
{
public int Id { get; set; }
public string y { get; set; }
}
public class Table
{
public int Id { get; set; }
public string x { get; set; }
}
结果:
我想在我的页面上添加简单的点赞功能(仅显示数据)。
我的页面后面有 PageModel 中的方法(这只是示例,因为我的页面太复杂了):
(..)getting DB context and stuff
public string bookName {get;set;}
public string someVariable1 {get;set;}
public List<string> _bookTags {get;set;}
public int LikeCounter {get;set;}
public void OnGet(){
someVariable1 = (from u in _context.table
where something==something
select u.x);
_bookTags= (from u in _context.bookTags
where something==something
select u.y).ToList();
LikeCounter = (from u in _context.likes
where u.book==bookName
select u).Count();
}
public void OnPost(){
likes newLike = new likes();
newLike.userName = HttpContext.User.Identity.Name.Split("\")[1];
newLike.book = bookName;
_context.likes.add(newLike);
_context.SaveChanges();
}
页面如下所示:
(..)
<div class="col-lg-4">
<form method="post">
<button class="btn btn-reddit" type="submit">LikeThisBook</button>
</form>
Current likes: @Model.LikeCounter
</div>
(..)
@foreach(string x in Model._bookTags){
<div class="border">
@x
</div>
}
(..)
所以问题是当我显示页面时 - 一切正常,但是当我单击“LikeThisBook”时 - OnPost 方法触发,为这本书添加用户名的喜欢...然后页面显示错误:
ArgumentNullException: Value cannot be null. (Parameter 'source')
并在堆栈跟踪中:
SomeProjectName.Pages.SomeBookStore.Pages_SomeBookStore_ShowBook.ExecuteAsync() in ShowBook.cshtml
@foreach(string x in Model._bookTags){ <- this is colored red
所以看起来在“OnGet”方法中填充的每个变量现在都是空的...
请帮忙:)
如果您不想重新加载页面并希望更新 counter.The,常用方法是使用 ajax。
这是一个工作演示:
Index.cshtml:
@page
@model IndexModel
<div class="col-lg-4">
<form method="post">
<input name="bookName" />
<button type="button" class="btn btn-reddit" onclick="Add()">LikeThisBook</button>
</form>
Current likes: <label>@Model.LikeCounter</label> @*add this*@
</div>
@foreach (string x in Model._bookTags)
{
<div class="border">
@x
</div>
}
@section Scripts
{
<script>
function Add() {
$.ajax({
type: "post",
beforeSend: function (xhr) {
xhr.setRequestHeader("XSRF-TOKEN",
$('input:hidden[name="__RequestVerificationToken"]').val());
},
success: function (data) {
$("label").html(data);
},
error: function () {
alert("Fail to add");
}
});
}
</script>
}
Index.cshtml.cs:
public class IndexModel : PageModel
{
private readonly RazorProj3_1Context _context;
public IndexModel(RazorProj3_1Context context)
{
_context = context;
}
[BindProperty]
public string bookName { get; set; }
public string someVariable1 { get; set; }
public List<string> _bookTags { get; set; }
public int LikeCounter { get; set; }
public void OnGet()
{
someVariable1 = (from u in _context.table
where u.Id == 1
select u.x).FirstOrDefault();
_bookTags = (from u in _context.bookTags
select u.y).ToList();
LikeCounter = (from u in _context.likes
//where u.book == bookName
select u).Count();
}
public ActionResult OnPost()
{
like newLike = new like();
newLike.book = bookName;
_context.likes.Add(newLike);
_context.SaveChanges();
LikeCounter = (from u in _context.likes
//where u.book == bookName
select u).Count();
return new JsonResult(LikeCounter);
}
}
Startup.cs:
services.AddAntiforgery(o => o.HeaderName = "XSRF-TOKEN");
我的测试模型:
public class likes
{
public int Id { get; set; }
public string book { get; set; }
}
public class BookTag
{
public int Id { get; set; }
public string y { get; set; }
}
public class Table
{
public int Id { get; set; }
public string x { get; set; }
}
结果: