It spose that tempdata read once and disposed and that was ok before using it as attribute now when using it like attribute it retain to next request after read for first time
here is my sample code
Page A
public class AModel : PageModel
{
[TempData]
public string Message { get; set; }
public void OnGet()
{
Message = "test Page A";
}
}
<h1>A</h1>
<p>#Model.Message</p>
<a asp-page="b">Page B</a>
Page B
public class BModel : PageModel
{
[TempData]
public string Message { get; set; }
public void OnGet()
{
}
}
<h1>B</h1>
<p>#Model.Message</p>
<a asp-page="A">Page A</a>
when navigating from page A to page b it should not showing the message from page A but i got the message appear in page B the result look like that
B
test Page A
Page A
when navigating from page A to page b it should not showing the message from page A
If you do a test with following code, you would easily find that the code snippet #Model.Message in A.cshtml does not read TempData value.
<h1>A</h1>
using TempData["Message"]: <p>#TempData["Message"]</p>
<hr />
using Model.Message: <p>#Model.Message</p>
<hr />
using TempData.Peek("Message"): <p>#TempData.Peek("Message")</p>
<hr />
using Model.Message: <p>#Model.Message</p>
<a asp-page="b">Page B</a>
The output of above testing
And as mentoned about TempData in this doc:
This property stores data until it's read in another request.
Related
Moving from ASP.NET Core MVC to Razor pages, there must be an issue in my understanding of passing data to a Razor view.
Here's a simple view:
#page
#model TestModel
#{
System.Diagnostics.Debug.WriteLine(Model.Name);
}
<form class="form-horizontal" method="get">
Name: <input type="text" class="form-control" asp-for="Name">
<button type="submit" class="btn btn-default">Send...</button>
</form>
And here is the view model class with one event handler:
public class TestModel : PageModel
{
[BindProperty(SupportsGet = true)]
public string Name { get; set; } = "";
public TestModel() {}
public IActionResult OnGet()
{
Name += "N";
return Page();
}
}
Then running the project:
Debug.WriteLine shows "N" as expected
input fields has "N" default value as expected
overwrite "N" in the input field eg. to "A" then press Send button
Debug.WriteLine shows "AN" as expected so view has got the value modified by OnGet()
the input field in the page itself contains the value "A" instead of "AN", the generated HTML contains:
value="A"
View does not render the modified Model.Name value but the original from the form data.
How can it be corrected to make view to render the modified string?
You can try to add ModelState.Clear(); in OnGet handler.When binding data in client side,it will get value from ModelState prior to Model.
public class TestModel : PageModel
{
[BindProperty(SupportsGet = true)]
public string Name { get; set; } = "";
public TestModel() {}
public IActionResult OnGet()
{
Name += "N";
ModelState.Clear();
return Page();
}
}
I'm using .NET 6 and razor pages.
[PageRemote] attribute in POST method doesn't send __requestverificationtoken to server and I get error 400.
This is my ViewModel
public class AddCategory
{
[PageRemote(PageName = "Category", PageHandler = "CheckForTitle",
HttpMethod = "POST",
AdditionalFields = "__RequestVerificationToken",
ErrorMessage = "This title is duplicate")]
public string Title { get; set; } = null!;
}
And this is my handler
public class CategoryModel : PageModel
{
[BindProperty]
public AddCategory Category { get; set; }
public void OnGet()
{
}
public IActionResult OnPostCheckForTitle(AddCategory category)
{
return new JsonResult(category.Title == "a");
}
}
GET method is ok and everything is fine, but in POST method __requestverificationtoken doesn't send to the server and I get error 400.
The property that you are trying to validate is on a nested property. All fields listed in the AdditionalFields property will be prefixed with the nested property name when they are posted, so the request verification token will be posted as Category.__RequestVerificationToken. As a result, the request verification token itself is not found, and request verification fails resulting in the 400 status code.
You should add a separate string property to the PageModel, Title, then apply the PageRemote attribute to that and reference it in the input tag helper via asp-for. Once you are happy that the submission is valid, you can assign the posted Title value to the relevant property in your Category object and process as usual.
public class CategoryModel : PageModel
{
[BindProperty]
public AddCategory Category { get; set; }
[BindProperty, PageRemote(PageName = "Category", PageHandler = "CheckForTitle",
HttpMethod = "POST",
AdditionalFields = "__RequestVerificationToken",
ErrorMessage = "This title is duplicate")]
public string Title { get; set; } = null!;
public IActionResult OnPostCheckForTitle(AddCategory category)
{
return new JsonResult(Title == "a");
}
}
#Mike Brind has been explained very nice. One way you can split the property from model and use asp-for="PropertyName" instead of nested property.
Another way is just override the name by specifying the name attribute like below:
<form method="post">>
//if you use method="post", it will auto generate token
//if you do not use method="post", remember add token like below
#*#Html.AntiForgeryToken()*#
<div class="form-group">
<label asp-for="Category.Title"></label>
//add the name....
<input asp-for="Category.Title" name="Title" class="form-control" />
<span asp-validation-for="Category.Title" class="text-danger"></span>
</div>
</form>
#section Scripts
{
<partial name="_ValidationScriptsPartial" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery-ajax-unobtrusive/3.2.6/jquery.unobtrusive-ajax.js" integrity="sha256-v2nySZafnswY87um3ymbg7p9f766IQspC5oqaqZVX2c=" crossorigin="anonymous"></script>
}
I am wanting to create a custom tag helper in razor pages which binds to a custom model but the value is not being read back into the modal on post, below is my TagHelper code
[HtmlTargetElement("kenai-date", TagStructure = TagStructure.WithoutEndTag)]
public class Date : TagHelper
{
//public string Value { get; set; }
public ModelExpression AspFor { get; set; }
public override void Process(TagHelperContext context, TagHelperOutput output)
{
output.TagName = "input";
output.TagMode = TagMode.SelfClosing;
output.Attributes.Add("value", this.AspFor.Model);
}
}
I am using the TagHelper with the below code
<kenai-date asp-for="DateValue" />
'DateValue' is a public property on the page, when first rendering the page the value of DateValue is correctly visible in the TagHelper Input element, if I force an OnPost, the value is removed.
I have applied the same to a standard input element with asp-for set and that works fine so suspect I am missing something in my TagHelper.
Asp.net core bind model data with name attribute.You use a custom tag helper,so it will get html like <input value="xxx">.So when form post,you cannot bind model data with name attribute,and when return Page in OnPost handler,model data is null.You need to add name attribute to <kenai-date asp-for="DateValue" />.Here is a demo:
TestCustomTagHelper.cshtml:
<form method="post">
<kenai-date asp-for="DateValue" name="DateValue" />
<input type="submit" />
</form>
TestCustomTagHelper.cshtml.cs:
public class TestCustomTagHelperModel : PageModel
{
[BindProperty]
public string DateValue { get; set; }
public void OnGet()
{
DateValue = "sss";
}
public IActionResult OnPost()
{
return Page();
}
}
result:
I have been trying to pass parameters trough another page and this works, however i'm not getting what I desired and it has probably to do with what i pass.
The first thing i pass is a name but includes spaces and special character, the second thing i pass is a web link
how i send it:
<div class="col-sm-4">
<h3>Programming</h3>
#if (programming == null)
{
<p><em>Loading...</em></p>
}
else
{
foreach (var program in programming)
{
#program.Name
<br />
}
}
</div>
where it goes to
#page "/CourseDetails"
#using Portfolio.Models;
#using Portfolio_Frontend.Data;
#using Microsoft.AspNetCore.WebUtilities
#inject NavigationManager NavigationHelper
<h3>CourseDetails</h3>
#if (Name == null)
{
<p><em>Loading...</em></p>
}
else
{
<p>#Name</p>
}
#code {
public string Name { get; set; }
protected override void OnInitialized()
{
var uri = NavigationHelper.ToAbsoluteUri
(NavigationHelper.Uri);
if (QueryHelpers.ParseQuery(uri.Query).
TryGetValue("name", out var name))
{
Name = name.First();
}
}
}
i tried parameters as well and now tried query string gives the same result.
the name it should pass in this particular case is: C# Intermediate: Classes, Interfaces and OOP
What i get is only 'C' I assume because it is not able to translate the #.
is there a way to pass literal strings?
where it goes to: https://localhost:5105/CourseDetails/?name=C#%20Intermediate:%20Classes,%20Interfaces%20and%20OOP
this seems right to me.
Minor correction of URL syntax methodology
You have:
#program.Name
Which has a URL of /CourseDetails/?name=C#
Normally, you would do either
/CourseDetails/C#
/CourseDetails?name=C#
Except, Blazor doesn't explicitly support optional route parameters (/CourseDetails?name=C#)
REF: https://blazor-university.com/routing/optional-route-parameters/#:~:text=Optional%20route%20parameters%20aren%E2%80%99t%20supported%20explicitly%20by%20Blazor,,then%20replace%20all%20references%20to%20currentCount%20with%20CurrentCount.
It looks as though you can keep the optional query parameters and fiddle with the QueryHelpers.ParseQuery() I don't quite buy into that but if you want to keep going that route check out this post by #chris sainty
Link: https://chrissainty.com/working-with-query-strings-in-blazor/
I would much rather create a new model (DTO) that knows exactly how to display the CourseDetails name in a URL encoded fashion for the link, and the display name for the user.
public class ProgramModel
{
private readonly string name;
public ProgramModel(string name)
{
this.name = name;
}
public string DisplayName => name;
public string RelativeUrl => HttpUtility.UrlEncode(name);
}
And when we need to render the links on the 'Courses' page, it would look like this:
#page "/courses"
#using BlazorApp1.Data
<div class="col-sm-4">
<h3>Programming</h3>
#foreach (var program in programming)
{
#program.DisplayName
<br />
}
</div>
#code {
public IEnumerable<ProgramModel> programming { get; set; }
protected override void OnInitialized()
{
programming = new List<ProgramModel>()
{
new ProgramModel("Rust Things"),
new ProgramModel("JavaScript Things"),
new ProgramModel("C# Things")
};
}
}
And finally, when displaying the CourseDetails page, we can simply decode the name from the URL with the same utility that encoded the string in the first place, instead of guessing whether or not it's the apps fault, or the browsers fault that the '#' is not getting encoded properly to '%23'
#page "/CourseDetails/{Name}"
#inject NavigationManager NavigationHelper
#using System.Web
<h3>CourseDetails</h3>
<p>#HttpUtility.UrlDecode(Name)</p>
#code {
[Parameter]
public string Name { get; set; }
}
I recommend letting go of the idea of navigating from page to page, and using components:
<div>
#if (SelectedItem is not null)
{
<MyResultsPage SelectedProgramClass=#SelectedItem />
}
</div>
#code
{
ProgramClass SelectedItem {get; set;}
void SomeWayToSelectMyItem(ProgramClass newSelection){
SelectedItem = newSelection;
StateHasChanged();
}
}
Then in your display page, MyResultsPage.blazor
<div>
<div>#SelectedProgramClass.name</div>
. . .
</div>
#code {
[Parameter]
ProgramClass SelectedProgramClass{get; set;}
}
<MyResultsPage> will not show up in any way on the client, or even be initialized, until you've assigned something to SelectedProgramClass.
I created a new ASP.Net Core 2 (Razor Pages) Project
My model is:
public class FormularioGenerico
{
public FormularioGenerico()
{
}
public string IP { get; set; }
public List<string> items { get; set; } = new List<string>();
}
On the page I put
on the page.cshtml.cs
public class EditarModel : PageModel
{
[BindProperty]
public FormularioGenerico ff { get; set; }
[BindProperty]
public string Message { get; set; }
public void OnGet()
{
this.ff = new FormularioGenerico();
ff.IP = "C# FORM";
ff.items.Add("OK1");
ff.items.Add("OK2");
ff.items.Add("OK3");
}
public async Task<IActionResult> OnPostAsync()
{
if (!ModelState.IsValid)
{
return Page();
}
var m = ModelState.IsValid; // true
Debug.WriteLine(this.ff.IP); // is Always returning null
Debug.WriteLine(this.ff.items.Count); // is Always returning null
}
}
on the page.cshtml:
#model Formulario.Pages.EditarModel
...
<h1>#Model.ff.IP</h1>
#foreach (var i in Model.ff.items)
{
<div>#i</div>
}
<button type="submit">Enviar</button>
The items are correctly output. But the complete object does not go to the OnPost.
The problem is: The model is not coming fully populated on the OnPost.
How to receive the full object that was created on the OnGet, plus the changes made by the user on the form, on the post to OnPostAsync() ?
The BindProperty attribute is used to inform ASP.NET Core that the values that the form submitted should be mapped to the specified object. In your case you set the values for the ff property but you do not have the equivalent input values so that ASP.NET Core will get these values in order to store them back to the ff property.
In order to make it work you will have to replace your razor code with the following code:
<form method="post">
<h1>#Model.ff.IP</h1>
<input asp-for="#Model.ff.IP" type="hidden" /> #* create a hidden input for the IP *#
#for (int i = 0; i < Model.ff.items.Count(); i++)
{
<input asp-for="#Model.ff.items[i]" type="hidden" /> #* create a hidden input for each item in your list *#
<div>#Model.ff.items[i]</div>
}
<button type="submit">Enviar</button>
</form>
Very important. To make this work you can not use the foreach loop because ASP.NET core will not be able to find the values. You will have to use a for loop.
The inputs that I added are hidden because I guess you do not want them to be visible but you can remore the type="hidden" so that you will be able to see them. Every change that you make to these inputs will be submitted to the OnPostAsync method.