如何讀取 .NET Core 中的連接字符串？

Question

我只想從配置文件中讀取一個連接字符串，為此將一個名為“appsettings.json”的文件添加到我的項目中，並在其上添加以下內容：

{
"ConnectionStrings": {
  "DefaultConnection": "Server=(localdb)\\mssqllocaldb;Database=aspnet-

 WebApplica71d622;Trusted_Connection=True;MultipleActiveResultSets=true"
  },
    "Logging": {
    "IncludeScopes": false,
    "LogLevel": {
    "Default": "Debug",
    "System": "Information",
    "Microsoft": "Information"
   }
 }
}

在 ASP.NET 我用這個：

 var temp=ConfigurationManager.ConnectionStrings["DefaultConnection"].ConnectionString;

現在我如何讀取 C# 中的“DefaultConnection”並將其存儲在 .NET Core 中的字符串變量中？

Answer 1

發布的答案很好，但沒有直接回答我在連接字符串中閱讀的相同問題。 通過大量搜索，我找到了一種稍微簡單的方法。

在 Startup.cs 中

public void ConfigureServices(IServiceCollection services)
{
    ...
    // Add the whole configuration object here.
    services.AddSingleton<IConfiguration>(Configuration);
}

在您的控制器中，在構造函數上添加一個配置字段和一個參數

private readonly IConfiguration configuration;

public HomeController(IConfiguration config) 
{
    configuration = config;
}

現在稍后在您的視圖代碼中，您可以像這樣訪問它：

connectionString = configuration.GetConnectionString("DefaultConnection");

Answer 2

您可以使用 GetConnectionString 擴展方法執行此操作：

string conString = Microsoft
   .Extensions
   .Configuration
   .ConfigurationExtensions
   .GetConnectionString(this.Configuration, "DefaultConnection");

System.Console.WriteLine(conString);

或為 DI 使用結構化類：

public class SmtpConfig
{
    public string Server { get; set; }
    public string User { get; set; }
    public string Pass { get; set; }
    public int Port { get; set; }
}

啟動：

public IConfigurationRoot Configuration { get; }


// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
    // http://developer.telerik.com/featured/new-configuration-model-asp-net-core/
    // services.Configure<SmtpConfig>(Configuration.GetSection("Smtp"));
    Microsoft.Extensions.DependencyInjection.OptionsConfigurationServiceCollectionExtensions.Configure<SmtpConfig>(services, Configuration.GetSection("Smtp"));

然后在家庭控制器中：

public class HomeController : Controller
{

    public SmtpConfig SmtpConfig { get; }
    public HomeController(Microsoft.Extensions.Options.IOptions<SmtpConfig> smtpConfig)
    {
        SmtpConfig = smtpConfig.Value;
    } //Action Controller


    public IActionResult Index()
    {
        System.Console.WriteLine(SmtpConfig);
        return View();
    }

在 appsettings.json 中有這個：

"ConnectionStrings": {
"DefaultConnection": "Server=(localdb)\\mssqllocaldb;Database=aspnet-WebApplica71d622;Trusted_Connection=True;MultipleActiveResultSets=true"
},

"Smtp": {
    "Server": "0.0.0.1",
    "User": "user@company.com",
    "Pass": "123456789",
    "Port": "25"
  }

Answer 3

有關更多信息，請參閱鏈接： https : //docs.microsoft.com/en-us/ef/core/miscellaneous/connection-strings

JSON

    {
      "ConnectionStrings": {
        "BloggingDatabase": "Server=(localdb)\\mssqllocaldb;Database=EFGetStarted.ConsoleApp.NewDb;Trusted_Connection=True;"
      },
    }

C# 啟動.cs

public void ConfigureServices(IServiceCollection services)
{
    services.AddDbContext<BloggingContext>(options =>
        options.UseSqlServer(Configuration.GetConnectionString("BloggingDatabase")));
}

編輯：aspnetcore，從 3.1 開始： https ://docs.microsoft.com/en-us/aspnet/core/fundamentals/configuration/?view = aspnetcore-3.1

Answer 4

我發現解決這個問題的方法是在 Startup 的構建器中使用 AddJsonFile（它允許它找到存儲在 appsettings.json 文件中的配置），然后使用它來設置私有 _config 變量

public Startup(IHostingEnvironment env)
    {
        var builder = new ConfigurationBuilder()
            .SetBasePath(env.ContentRootPath)
            .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
            .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true)
            .AddEnvironmentVariables();
        _config = builder.Build();
    }

然后我可以如下設置配置字符串：

var connectionString = _config.GetConnectionString("DbContextSettings:ConnectionString"); 

這是在 dotnet core 1.1 上

Answer 5

ASP.NET Core （在我的例子中是3.1 ）為我們提供了對Controllers 的構造函數注入，所以你可以簡單地添加以下構造函數：

[Route("api/[controller]")]
[ApiController]
public class TestController : ControllerBase
{
    private readonly IConfiguration m_config;

    public TestController(IConfiguration config)
    {
        m_config = config;
    }

    [HttpGet]
    public string Get()
    {
        //you can get connection string as follows
        string connectionString = m_config.GetConnectionString("Default")
    }
}

appsettings.json 可能如下所示：

{
    "ConnectionStrings": {
        "Default": "YOUR_CONNECTION_STRING"
        }
}

Answer 6

我是這樣做的：

我在 appsettings.json 添加了連接字符串

"ConnectionStrings": {
"conStr": "Server=MYSERVER;Database=MYDB;Trusted_Connection=True;MultipleActiveResultSets=true"},

我創建了一個名為 SqlHelper 的類

public class SqlHelper
{
    //this field gets initialized at Startup.cs
    public static string conStr;

    public static SqlConnection GetConnection()
    {
        try
        {
            SqlConnection connection = new SqlConnection(conStr);
            return connection;
        }
        catch (Exception e)
        {
            Console.WriteLine(e);
            throw;
        }
    }
}

在 Startup.cs 中，我使用 ConfigurationExtensions.GetConnectionString 來獲取連接，並將其分配給 SqlHelper.conStr

public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
        SqlHelper.connectionString = ConfigurationExtensions.GetConnectionString(this.Configuration, "conStr");
    }

現在無論你在哪里需要連接字符串，你只需像這樣調用它：

SqlHelper.GetConnection();

Answer 7

還有另一種方法。 在我的示例中，您會看到存儲庫類中的一些業務邏輯，我在 ASP .NET MVC Core 3.1 中使用了依賴注入。

在這里，我想為該業務邏輯獲取connectiongString ，因為可能另一個存儲庫完全可以訪問另一個數據庫。

這種模式允許您在同一個業務邏輯存儲庫中訪問不同的數據庫。

C＃

public interface IStatsRepository
{
            IEnumerable<FederalDistrict> FederalDistricts();
}

class StatsRepository : IStatsRepository
{
   private readonly DbContextOptionsBuilder<EFCoreTestContext>
                optionsBuilder = new DbContextOptionsBuilder<EFCoreTestContext>();
   private readonly IConfigurationRoot configurationRoot;

   public StatsRepository()
   {
       IConfigurationBuilder configurationBuilder = new ConfigurationBuilder().SetBasePath(Environment.CurrentDirectory)
           .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true);
       configurationRoot = configurationBuilder.Build();
   }

   public IEnumerable<FederalDistrict> FederalDistricts()
   {
        var conn = configurationRoot.GetConnectionString("EFCoreTestContext");
        optionsBuilder.UseSqlServer(conn);

        using (var ctx = new EFCoreTestContext(optionsBuilder.Options))
        { 
            return ctx.FederalDistricts.Include(x => x.FederalSubjects).ToList();
        }
    }
}

appsettings.json

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft": "Warning",
      "Microsoft.Hosting.Lifetime": "Information"
    }
  },
  "AllowedHosts": "*",
  "ConnectionStrings": {
    "EFCoreTestContext": "Data Source=DESKTOP-GNJKL2V\\MSSQLSERVER2014;Database=Test;Trusted_Connection=True;MultipleActiveResultSets=true"
  }
}

Answer 8

在 3.1 中，已經為“ConnectionStrings”定義了一個部分

系統.配置.連接字符串設置

定義：

  "ConnectionStrings": {
    "ConnectionString": "..."
  }

注冊：

public void ConfigureServices(IServiceCollection services)
{
     services.Configure<ConnectionStringSettings>(Configuration.GetSection("ConnectionStrings"));
}

注入：

public class ObjectModelContext : DbContext, IObjectModelContext
{

     private readonly ConnectionStringSettings ConnectionStringSettings;

    ...

     public ObjectModelContext(DbContextOptions<ObjectModelContext> options, IOptions<ConnectionStringSettings> setting) : base(options)
    {
          ConnectionStringSettings = setting.Value;
    }

    ...
}

使用：

   public static void ConfigureContext(DbContextOptionsBuilder optionsBuilder, ConnectionStringSettings connectionStringSettings)
    {
        if (optionsBuilder.IsConfigured == false)
        {
            optionsBuilder.UseLazyLoadingProxies()
                          .UseSqlServer(connectionStringSettings.ConnectionString);
        }
    }

Answer 9

如果您想從 appsettings.json 獲取一個連接字符串到 Model 或 ViewModel（不是控制器），下面的方法可以正常工作。 這適用於 ASP.NET Core 3 及更高版本。 有時您可能需要將 connectionString 放入 Model （用於 SQL 查詢）而不是通過 controller 進行依賴注入，因此下面的此方法將從 appsettings 獲取您的連接字符串：

public class NameOfYourModel
{
  static class getConnection
  {
    public static IConfigurationRoot Configuration;
    public static string GetConnectionString()
    {
      var builder = new ConfigurationBuilder()
      .SetBasePath(System.IO.Directory.GetCurrentDirectory())
      .AddJsonFile("appsettings.json");
       Configuration = builder.Build();
       var connectionString =   
    Configuration.GetConnectionString("connectionStringName");
       
       return connectionString;
     }
    }
    string connStr = getConnection.GetConnectionString().ToString(); //This   
   //line now has your connectionString which you can use. 

 //Continue the rest of your code here.
}

Answer 10

太晚了，但在閱讀了所有有用的答案和評論后，我最終使用了Microsoft.Extensions.Configuration.Binder擴展包，並嘗試擺脫了硬編碼的配置鍵。

我的解決方案：

IConfigSection.cs

public interface IConfigSection
{
}

配置擴展.cs

public static class ConfigurationExtensions
{
    public static TConfigSection GetConfigSection<TConfigSection>(this IConfiguration configuration) where TConfigSection : IConfigSection, new()
    {
        var instance = new TConfigSection();
        var typeName = typeof(TConfigSection).Name;
        configuration.GetSection(typeName).Bind(instance);

        return instance;
    }
}

appsettings.json

{
   "AppConfigSection": {
      "IsLocal": true
   },
   "ConnectionStringsConfigSection": {
      "ServerConnectionString":"Server=.;Database=MyDb;Trusted_Connection=True;",
      "LocalConnectionString":"Data Source=MyDb.db",
   },
}

要訪問強類型配置，您只需要為此創建一個類，該類實現IConfigSection接口（注意：類名和字段名應與appsettings.json中的部分完全匹配）

AppConfigSection.cs

public class AppConfigSection: IConfigSection
{
    public bool IsLocal { get; set; }
}

ConnectionStringsConfigSection.cs

public class ConnectionStringsConfigSection : IConfigSection
{
    public string ServerConnectionString { get; set; }
    public string LocalConnectionString { get; set; }

    public ConnectionStringsConfigSection()
    {
        // set default values to avoid null reference if
        // section is not present in appsettings.json
        ServerConnectionString = string.Empty;
        LocalConnectionString = string.Empty;
    }
}

最后，一個使用示例：

啟動文件

public class Startup
{
    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
    }

    public IConfiguration Configuration { get; }

    public void ConfigureServices(IServiceCollection services)
    {
        // some stuff

        var app = Configuration.GetConfigSection<AppConfigSection>();
        var connectionStrings = Configuration.GetConfigSection<ConnectionStringsConfigSection>();

        services.AddDbContext<AppDbContext>(options =>
        {
            if (app.IsLocal)
            {
                options.UseSqlite(connectionStrings.LocalConnectionString);
            }
            else
            {
                options.UseSqlServer(connectionStrings.ServerConnectionString);
            }
        });

        // other stuff
    }
}

為了使它整潔，您可以將上面的代碼移動到擴展方法中。

就是這樣，沒有硬編碼的配置鍵。

Answer 11

private readonly IConfiguration configuration;
        public DepartmentController(IConfiguration _configuration)
        {
            configuration = _configuration;
        }

        [HttpGet]
        public JsonResult Get()
        {
string sqlDataSource = configuration["ConnectionStrings:DefaultConnection"];

Answer 12

在 .NET Core 6 中

應用設置.json<\/strong>

 "ConnectionStrings": {
   "DefaultConnection": "Server=**Server Name**;Database=**DB NAME**;Trusted_Connection=True;MultipleActiveResultSets=true"
  }

Answer 13

我有一個數據訪問庫，它適用於 .net 核心和 .net 框架。

訣竅是在 .net 核心項目中將連接字符串保存在名為“app.config”的 xml 文件中（也適用於 Web 項目），並將其標記為“復制到輸出目錄”，

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <connectionStrings>
    <add name="conn1" connectionString="...." providerName="System.Data.SqlClient" />
  </connectionStrings>
</configuration>

ConfigurationManager.ConnectionStrings - 將讀取連接字符串。

    var conn1 = ConfigurationManager.ConnectionStrings["conn1"].ConnectionString;

Answer 14

您可以使用配置擴展方法：getConnectionString("DefaultConnection")

https://docs.asp.net/projects/api/en/latest/autoapi/Microsoft/Extensions/Configuration/ConfigurationExtensions/index.html#Microsoft.Extensions.Configuration.ConfigurationExtensions.GetConnectionString