如何在 .NET Core 中读取连接字符串？

Question

我只想从配置文件中读取一个连接字符串，为此向我的项目中添加一个名为“appsettings.json”的文件并在其上添加以下内容：

{
"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 上我使用了这个：

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

现在如何在 C# 中读取“DefaultConnection”并将其存储在 .NET Core 中的字符串变量中？

Answer 1

发布的答案很好，但没有直接回答我在连接字符串中阅读的相同问题。经过大量搜索，我发现了一种稍微简单的方法。

在 Startup.cs 中

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

在你的控制器中为配置添加一个字段，并在构造函数中为其添加一个参数

private readonly IConfiguration configuration;

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

现在稍后在您的视图代码中，您可以像这样访问它：

connectionString = configuration.GetConnectionString("DefaultConnection");

Answer 2

您可以使用 GetConnectionString 扩展方法来做到这一点：

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

System.Console.WriteLine(conString);

或为 DI 使用结构化类：

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

启动：

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 中有这个：

"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

查看链接了解更多信息： 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# Startup.cs

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

编辑：aspnetcore，从 3.1 开始： https://docs.microsoft.com/en-us/aspnet/core/fundamentals/configuration/?view=aspnetcore-3.1

Answer 4

我发现解决此问题的方法是在 Startup 的构建器中使用 AddJsonFile（它允许它找到存储在 appsettings.json 文件中的配置），然后使用它来设置私有 _config 变量

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();
    }

然后我可以如下设置配置字符串：

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

这是在 dotnet core 1.1 上

Answer 5

我就是这样做的：

我在 appsettings.json 中添加了连接字符串

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

我创建了一个名为 SqlHelper 的类

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 我使用 ConfigurationExtensions.GetConnectionString 来获取连接，并将其分配给 SqlHelper.conStr

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

现在只要你需要连接字符串，你就可以这样称呼它：

SqlHelper.GetConnection();

Answer 6

ASP.NET Core（在我的例子中是 3.1）为我们提供了构造函数注入到控制器中，所以您可以简单地添加以下构造函数：

[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 7

还有另一种方法。在我的示例中，您会在存储库类中看到一些业务逻辑，我在 ASP .NET MVC Core 3.1 中与依赖注入一起使用。

在这里，我想为该业务逻辑获取 connectiongString，因为可能另一个存储库将完全可以访问另一个数据库。

这种模式允许您在同一个业务逻辑存储库中访问不同的数据库。

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 中已经为“ConnectionStrings”定义了一个部分

System.Configuration.ConnnectionStringSettings

定义：

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

注册：

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

在 .NET Core 6 中

appsettings.json

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

Program.cs

var connectionString = builder.Configuration.GetConnectionString("DefaultConnection");
builder.Services.AddDbContext<ApplicationDbContext>(options => options.UseSqlServer(connectionString));

数据库上下文

public class ApplicationDbContext : DbContext
{
    public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options) : base(options)
    {

    }

}

Answer 10

为时已晚，但在阅读了所有有用的答案和 cmets 之后，我最终使用了 Microsoft.Extensions.Configuration.Binder 扩展包并尝试摆脱硬编码的配置键。

我的解决方案：

IConfigSection.cs

public interface IConfigSection
{
}

ConfigurationExtensions.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",
   },
}

要访问强类型配置，您只需要为此创建一个类，该类实现 IConfigSection 接口（注意：类名和字段名应完全匹配部分在 appsettings.json)

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;
    }
}

最后是一个用法示例：

Startup.cs

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
    }
}

为了简洁，你可以将上面的代码移到扩展方法中。

就是这样，没有硬编码的配置键。

Answer 11

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

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

Answer 12

您可以使用配置扩展方法：getConnectionString("DefaultConnection")

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

Answer 13

我有一个可与 .net 核心和 .net 框架一起使用的数据访问库。

诀窍是在 .net 核心项目中将连接字符串保存在名为“app.config”的 xml 文件中（也适用于 Web 项目），并将其标记为“复制到输出目录”，

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

ConfigurationManager.ConnectionStrings - 将读取连接字符串。

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