Net Core Connection String Dapper视觉工作室2017

Question

我试图在我的.Net Core应用程序中设置连接字符串,但我一直收到错误:

System.NullReferenceException:'对象引用未设置为对象的实例.'

我尝试将以下内容添加到appsettings.json:

"ConnectionStrings": {

"Analysis": "Server=DESKTOP-MYSERVER;Database=MYDATABASE;User Id=sa; Password=Password123;Provider=System.Data.SqlClient;Trusted_Connection=True;MultipleActiveResultSets=true;Pooling=false;"
}

我也试过像以前那样使用web.config .Net Core:

<connectionStrings>
<add name="Analysis" providerName="System.Data.SqlClient" 
     connectionString="Server=DESKTOP-MYSERVER;Database=MYDATABASE;User Id=sm;Password=Password123;"/>

然后在c#我有:

public List<DapperTest> ReadAll()
    {
        var data = new List<DapperTest>();
        using (IDbConnection db = new SqlConnection(ConfigurationManager.ConnectionStrings["Analysis"].ConnectionString))
        {
             data = db.Query<DapperTest>("select * from testTable").ToList();
        }

        return data;
    }

两种方式都给我例外:

System.NullReferenceException:'对象引用未设置为对象的实例.'

我使用了以下资源:

.Net CORE Dapper连接字符串？

https://docs.microsoft.com/en-us/aspnet/core/data/ef-mvc/intro

从App.config获取连接字符串

但我错过了一些东西.我只设置了一次连接字符串,它不在.Net Core中,因此对其他人来说可能是显而易见的.

Answer 1

如果您正在使用appsettings.json,请创建一个简单的POCO类来为您的连接字符串配置建模,如下所示:

public class ConnectionConfig
{
        public string Analysis {get;set;}
}

在Startup.cs中的ConfigureServices方法中添加此行

services.Configure<ConnectionConfig>(Configuration.GetSection("ConnectionStrings"));

数据服务类

class YourClass{
    private string _connectionString;

    YourClass(string connectionString){
       _connectionString = connectionString;
    }

    //Your implementation
    public List<DapperTest> ReadAll()
    {
        var data = new List<DapperTest>();
        using (IDbConnection db = new SqlConnection(_connectionString)
        {
            data = db.Query<DapperTest>("select * from testTable").ToList();
        }

       return data;
   }
}

IOptions<ConnectionConfig>在控制器构造函数中注入.

class YourController : Controller{
   YourClass _testing;

   YourController(IOptions<ConnectionConfig> connectionConfig){
       var connection = connectionConfig.Value;
       string connectionString = connection.Analysis;
       _testing = new YourClass(connectionString );
    }
   public IActionResult Index() { 
        var testingData = _testing.ReadAll(); 
        return View(); 
     }
 }