我使用ASP.net核心創建了一個簡單的CRUD應用程式

這是我的更新頁面代碼。

using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;
using System.Data.SqlClient;

namespace WebApplication2.Pages.Users
{
    public class EditModel : PageModel
    {
        public UserInfo userInfo = new UserInfo();
        public String errorMessage = "";
        public String successMessage = "";
        public void OnGet()
        {
            String id=Request.Query["id"];

            try
            {
                String connectionString = "Data Source=DESKTOP-5406L1M;Initial Catalog=crud;Integrated Security=True";
                using (SqlConnection connection = new SqlConnection(connectionString))
                {
                    connection.Open();
                    String sql = "SELECT * FROM users WHERE id=@id";
                    using (SqlCommand command = new SqlCommand(sql, connection))
                    {
                        command.Parameters.AddWithValue("@id", id);
                        using (SqlDataReader reader = command.ExecuteReader())
                        {
                            while (reader.Read())
                            {
                                userInfo.id = "" reader.GetInt32(0);
                                userInfo.name = reader.GetString(1);
                                userInfo.email = reader.GetString(2);
                                userInfo.phone = reader.GetString(3);
                                userInfo.address = reader.GetString(4);
                            }
                        }
                    }
                }
            }
            catch(Exception ex)
            {
                errorMessage = ex.Message;
            }
        }

        public void OnPost()
        {
            userInfo.id = Request.Form["id"];
            userInfo.name = Request.Form["name"];
            userInfo.email = Request.Form["email"];
            userInfo.phone = Request.Form["phone"];
            userInfo.address = Request.Form["address"];

            if (userInfo.id.Length==0 ||userInfo.name.Length == 0 || userInfo.email.Length == 0 || userInfo.phone.Length == 0 || userInfo.address.Length == 0)
            {
                errorMessage = "All the field are required";
                return;
            }

            try
            {
                String connectionString = "Data Source=DESKTOP-5406L1M;Initial Catalog=crud;Integrated Security=True";
                using (SqlConnection connection = new SqlConnection(connectionString))
                {
                    connection.Open();
                    String sql ="UPDATE users "  
                               "SET name=@name, email=@email, phone=@phone, address=@address "  
                               "WHERE id=@id";
                    using (SqlCommand command = new SqlCommand(sql, connection))
                    {
                       
                        command.Parameters.AddWithValue("@name", userInfo.name);
                        command.Parameters.AddWithValue("@email", userInfo.email);
                        command.Parameters.AddWithValue("@phone", userInfo.phone);
                        command.Parameters.AddWithValue("@address", userInfo.address);
                        command.Parameters.AddWithValue("@id", userInfo.id);

                        command.ExecuteNonQuery();
                    }
                }
            }
            catch(Exception ex)
            {
                errorMessage=ex.Message;
                return;
            }
            Response.Redirect("/Users/Index");
        }
    }
}

`

這是我的索引頁面（userInfo 類）

索引頁面（userInfo 類）

using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;
using System.Data.SqlClient;

namespace WebApplication2.Pages.Users
{
    public class IndexModel : PageModel
    {
        public List<UserInfo> ListUsers=new List<UserInfo>();
        public void OnGet()
        {
            try
            {
                String connectionString = "Data Source=DESKTOP-5406L1M;Initial Catalog=crud;Integrated Security=True";
                using (SqlConnection connection = new SqlConnection(connectionString))
                {
                    connection.Open();
                    String sql = "SELECT * FROM users";
                    using (SqlCommand command =new SqlCommand(sql, connection))
                    {
                        using (SqlDataReader reader = command.ExecuteReader())
                        {
                            while (reader.Read())
                            {
                                UserInfo userInfo = new UserInfo();
                                userInfo.id = ""   reader.GetInt32(0);
                                userInfo.name = reader.GetString(1);
                                userInfo.email = reader.GetString(2);
                                userInfo.phone = reader.GetString(3);
                                userInfo.address = reader.GetString(4);
                                userInfo.created_at = reader.GetDateTime(5).ToString();

                                ListUsers.Add(userInfo);
                            }
                        }
                    }
                }
            }
            catch(Exception ex)
            {
                Console.WriteLine("Exception:"   ex.ToString());
            }
        }
    }

    public class UserInfo
    {
        public string id;
        public string name;
        public string email;
        public string phone;
        public string address;
        public string created_at;
    }
}

在更新頁面上，我收到了一個錯誤

**將 nvarchar 值 '=2' 轉換為資料型別 int 時轉換失敗。**誰能幫我解決它？我的代碼似乎是正確的。但我有一個錯誤。..................................................................

資料庫結構

但是，關于code readibility，我不太確定您為什么要pattern關注update and display your list. 您甚至可以以最簡單的方式做到這一點，如下保持ADO.NET fashion

另一種實作方式：

全域變數：

        List<UserInfo> ListUsers = new List<UserInfo>();
        UserInfo userInfo = new UserInfo();
        public String errorMessage = "";
        public String successMessage = "";

控制器：串列視圖：

        public IActionResult Index()
        {
         
            string connectionString = "Data Source=WX-6899;Initial Catalog=WsAttendance;Integrated Security=True";
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                connection.Open();
                String sql = "SELECT * FROM userCaseSO";
                using (SqlCommand command = new SqlCommand(sql, connection))
                {
                    using (SqlDataReader reader = command.ExecuteReader())
                    {
                        while (reader.Read())
                        {
                            UserInfo userInfo = new UserInfo();
                            userInfo.id = ""   reader.GetInt32(0);
                            userInfo.name = reader.GetString(1);
                            userInfo.email = reader.GetString(2);
                            userInfo.phone = reader.GetString(3);
                            userInfo.address = reader.GetString(4);


                            ListUsers.Add(userInfo);
                        }
                    }
                }
            }
            return View(ListUsers);
        }

視圖應如下所示：

編輯控制器動作：

public IActionResult Edit(string Id)
        {
           
            string connectionString = "Data Source=WX-6899;Initial Catalog=WsAttendance;Integrated Security=True";
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                connection.Open();
                String sql = "SELECT * FROM userCaseSO WHERE id=@id";
                using (SqlCommand command = new SqlCommand(sql, connection))
                {
                    command.Parameters.AddWithValue("@id", Id);
                    using (SqlDataReader reader = command.ExecuteReader())
                    {
                        while (reader.Read())
                        {
                            userInfo.id = ""   reader.GetInt32(0);
                            userInfo.name = reader.GetString(1);
                            userInfo.email = reader.GetString(2);
                            userInfo.phone = reader.GetString(3);
                            userInfo.address = reader.GetString(4);
                        }
                    }
                }
            }

            return View(userInfo);

        }

編輯視圖：

@model DotNet6MVCWebApp.Models.UserInfo
<div>
    <form asp-action="OnPost" asp-controller="AdoDotNetUserUpdate" method="post" enctype="multipart/form-data">

        <div>
            <h4><strong>Update Info</strong> </h4>

            <table class="table table-sm table-bordered table-striped">

                <tr>
                    <th> <label asp-for="id"></label></th>
                    <td> <input asp-for="id" class="form-control" readonly placeholder="Enter name" /><span asp-validation-for="id"></span></td>
                </tr>
                <tr>
                    <th> <label asp-for="name"></label></th>
                    <td> <input asp-for="name" class="form-control" placeholder="Enter name" /><span asp-validation-for="name"></span></td>
                </tr>
                <tr>
                    <th> <label asp-for="email"></label></th>
                    <td> <input asp-for="email" class="form-control" placeholder="Enter email" /><span asp-validation-for="email"></span></td>
                </tr>
                <tr>
                    <th> <label asp-for="phone"></label></th>
                    <td> <input asp-for="phone" class="form-control" placeholder="Enter phone" /><span asp-validation-for="phone"></span></td>
                </tr>
                <tr>
                    <th> <label asp-for="address"></label></th>
                    <td> <input asp-for="address" class="form-control" placeholder="Enter address" /><span asp-validation-for="address"></span></td>
                </tr>
                <tr>
                    <th>  <button type="submit" class="btn btn-primary" style="width:107px">Update</button></th>
                    <td> </td>
                </tr>
                <tr>
                    <th>@Html.ActionLink("Back To List", "Index", new { /* id=item.PrimaryKey */ }, new { @class = "btn btn-success" })</th>
                    <td> </td>
                </tr>
            </table>
        </div>
    </form>

</div>

編輯視圖頁面應如下所示：

編輯提交控制器：

        [HttpPost]
        public IActionResult OnPost()
        {
            userInfo.id = Request.Form["id"];
            userInfo.name = Request.Form["name"];
            userInfo.email = Request.Form["email"];
            userInfo.phone = Request.Form["phone"];
            userInfo.address = Request.Form["address"];

            if (userInfo.id.Length == 0 || userInfo.name.Length == 0)
            {
                errorMessage = "All the field are required";
               
            }

            try
            {
                String connectionString = "Data Source=WX-6899;Initial Catalog=WsAttendance;Integrated Security=True";
                using (SqlConnection connection = new SqlConnection(connectionString))
                {
                    connection.Open();
                    String sql = "UPDATE userCaseSO "  
                               "SET name=@name, email=@email, phone=@phone, address=@address "  
                               "WHERE id=@id";
                    using (SqlCommand command = new SqlCommand(sql, connection))
                    {

                        command.Parameters.AddWithValue("@name", userInfo.name);
                        command.Parameters.AddWithValue("@email", userInfo.email);
                        command.Parameters.AddWithValue("@phone", userInfo.phone);
                        command.Parameters.AddWithValue("@address", userInfo.address);
                        command.Parameters.AddWithValue("@id", userInfo.id);

                        command.ExecuteNonQuery();
                    }
                }
               
            }
            catch (Exception ex)
            {
                errorMessage = ex.Message;
             
            }
            return RedirectToAction("Index");
        }

最終輸出：

注意：考慮到您的理解，甚至還有優雅的實作方式，目前可以在此級別進行改進。

uj5u.com熱心網友回復：

您收到此錯誤是因為您嘗試將列 DataType 從 String 轉換為 int，這是不正確的。您可以嘗試將IDas Integer轉換為

 CAST(@ID AS int) 

或者

CONVERT(int,@ID)

標籤：C＃asp.net 核心asp.net-core-mvc

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