[英]How to connect sql Database with ado.net in Asp.Net Core Mvc 5.0?
我找不到我在哪里失蹤。 我的代碼是這樣的;
用戶.cs:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.Data.SqlClient;
using System.Configuration;
using System.Data;
namespace Adonet_Sql.Models
{
public class users
{
private string connectionString = ConfigurationManager.ConnectionStrings["DefaultConnection"].ConnectionString;
public List<usersAccessLayer> getdata()
{
List<usersAccessLayer> li = new List<usersAccessLayer>();
try
{
SqlConnection conn = new SqlConnection(connectionString);
SqlCommand cmd = new SqlCommand("test", conn);
conn.Open();
cmd.CommandType = CommandType.StoredProcedure;
SqlDataReader rdr = cmd.ExecuteReader();
while (rdr.Read())
{
usersAccessLayer usr = new usersAccessLayer();
usr.id = (string)rdr.GetValue(2);
usr.name = rdr.GetString(0);
usr.surname = rdr.GetString(1);
li.Add(usr);
}
}
catch (Exception)
{
throw;
}
return li;
}
}
}
usersAccessLayer.cs;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
namespace Adonet_Sql.Models
{
public class usersAccessLayer
{
public string name { get; set; }
public string surname { get; set; }
public string id { get; set; }
}
}
appsettings.json
{
"ConnectionStrings": {
"DefaultConnection": "Server=DESKTOP-1FOQ86Q;
Database=Users;Trusted_Connection=True;MultipleActiveResultSets=true\""
},
"Logging": {
"LogLevel": {
"Default": "Information",
"Microsoft": "Warning",
"Microsoft.Hosting.Lifetime": "Information"
}
},
"AllowedHosts": "*"
}
最后我得到了這個錯誤;
處理請求時發生未處理的異常。 NullReferenceException:Object 引用未設置為 object 的實例。 users.cs 中的 Adonet_Sql.Models.users..ctor(),users.cs 中的第 14 行 Adonet_Sql.Models.users..ctor()
private string connectionString = ConfigurationManager.ConnectionStrings["DefaultConnection"].ConnectionString;
Adonet_Sql.Controllers.HomeController.Index() in HomeController.cs
sers obj = new users();
lambda_method1(Closure , object , object[] )
Microsoft.AspNetCore.Mvc.Infrastructure.ActionMethodExecutor+SyncActionResultExecutor.Execute(IActionResultTypeMapper mapper, ObjectMethodExecutor executor, object controller, object[] arguments)
布拉布拉。
ConfigurationManager.ConnectionStrings["DefaultConnection"].ConnectionString;
適用於 .net 核心 3.0
在 5.0 中你需要使用;
string connectionString = _configuration.GetConnectionString("DefaultConnection");
或者
private string connectionString = "Server=DESKTOP-1FOQ86Q ;Database=Users;Trusted_Connection=True;MultipleActiveResultSets=true"
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