here is my UPDATE page code.

using Microsoft.AspNetCore.Mvc;
usding 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");
        }
    }
}

` In the update page i got error

**Conversion failed when converting the nvarchar value '=2' to data type int. ** can anyone help me how to fix it?

CodePudding user response：

You got this error because you tried to convert column DataType from String to int which is not right. You may try to cast the ID as Integer like

 CAST(@ID AS int) 

or

CONVERT(int,@ID)

CodePudding user response：

**Conversion failed when converting the nvarchar value '=2' to data type int. ** can anyone help me how to fix it?

Well, the exact mistake has been done in public void OnPost() method on line userInfo.id = Request.Form["id"]; as it seems your userInfo.id is a type of int

Therefore, Request.Form["id"] will consider as string so you outght to parse it into userInfo.id = Convert.ToInt32(Request.Form["id"]);.

Nonetheless, userInfo.id.Length == 0 this operation is invalid on type int instead you should write userInfo.id == 0 in your if condition.

Output:

I have tested your code keeping id as string in the Model class that is Request.Form["id"] and its working as expected without any error. As you can see the below: So assuming value =2 has inserted mistakenly.