FormTagHelper : 為.net對html原生的封裝， 預設若沒指定method則是採用get提交。

新建好FormController.cs

using Microsoft.AspNetCore.Mvc;
using Net5App6.Models;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace Net5App6.Controllers
{
    public class FormController : Controller
    {
        [HttpGet]
        public IActionResult Index()
        {
            return View();
        }

        [HttpPost]
        public IActionResult Add(FormViewModel model)
        {
            if (ModelState.IsValid)
            {
                string name = model.Name;
                int age = model.Age;
                string remark = model.Remark;
            }
            return View(model);
        }
    }
}

FormViewModel.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace Net5App6.Models
{
    public class FormViewModel
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public int Age { get; set; }
        public string Remark { get; set; }
    }
}

Index.cshtml

@model FormViewModel
<form method="post" asp-controller="Form" asp-action="Add">
    <div>
        <label asp-for="Name"></label>
        <input type="text" asp-for="Name" />
    </div>
    <div>
        <label asp-for="Age"></label>
        <input type="text" asp-for="Age" />
    </div>
    <div>
        <label asp-for="Remark"></label>
        <textarea asp-for="Remark"></textarea>
    </div>
    <div>
        <input type="submit" value="提交" />
    </div>
</form>

防止跨站請求
預設情況FormTagHelper會在View上產生隱藏的請求用Token
但需要和HTTP Post的Action method上標註[ValidateAntiForgeryToken]才會生效，可以防止跨站請求偽造。

using Microsoft.AspNetCore.Mvc;
using Net5App6.Models;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace Net5App6.Controllers
{
    public class FormController : Controller
    {
        [HttpGet]
        public IActionResult Index()
        {
            return View();
        }

        [HttpPost]
        [ValidateAntiForgeryToken]
        public IActionResult Add(FormViewModel model)
        {
            if (ModelState.IsValid)
            {
                string name = model.Name;
                int age = model.Age;
                string remark = model.Remark;
            }
            return View(model);
        }
    }
}

自訂路由命名 asp-route
通常若不想多寫太多asp-controller 、asp-action等等屬性，想要簡寫時候可以用這類功能，
但要注意 路由名稱name不能夠有重覆，專案中要唯一。

這裡擴充一個action method 名稱Edit

using Microsoft.AspNetCore.Mvc;
using Net5App6.Models;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace Net5App6.Controllers
{
    public class FormController : Controller
    {
        [HttpGet]
        public IActionResult Index()
        {
            return View();
        }

        [HttpPost]
        [Route("/Form/EditData",Name ="R_E")]
        public IActionResult Edit(FormViewModel model)
        {
            return View(model);
        }

        [HttpPost]
        [ValidateAntiForgeryToken]
        public IActionResult Add(FormViewModel model)
        {
            if (ModelState.IsValid)
            {
                string name = model.Name;
                int age = model.Age;
                string remark = model.Remark;
            }
            return View(model);
        }
    }
}

Index.cshtml

@model FormViewModel
@*<form method="post" asp-controller="Form" asp-action="Add">*@
<form method="post" asp-route="R_E" >
    <div>
        <label asp-for="Name"></label>
        <input type="text" asp-for="Name" />
    </div>
    <div>
        <label asp-for="Age"></label>
        <input type="text" asp-for="Age" />
    </div>
    <div>
        <label asp-for="Remark"></label>
        <textarea asp-for="Remark"></textarea>
    </div>
    <div>
        <input type="submit" value="提交" />
    </div>
</form>

於專案中之前額外的範例練習我有在AnchorController
寫一個路由模板， 名稱為stu_show

這裡我把他故意改成一樣叫stu_show測試

當一運行即可看到錯誤

重導向路由
route-returnurl:可以允許指定重新跳轉到指定URL。
比方登入錯誤就重新跳轉到登入頁面、首頁或上一頁。

本篇已同步發表至個人部落格
https://coolmandiary.blogspot.com/2021/08/net-core21formtaghelper.html