如何在.NET Core中读取连接字符串？

Question

我想从配置文件中只读取一个连接字符串,并为此添加一个名为"appsettings.json"的文件到我的项目中,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;

现在我如何在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读取的相同问题.通过大量搜索,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);
}

在控制器中,在构造函数中为配置添加一个字段并为其添加一个参数

private readonly IConfiguration configuration;

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

现在稍后在您的视图代码中,您可以访问它:

connectionString = configuration.GetConnectionString("DefaultConnection");

Answer 2

您可以使用GetConnectionString扩展方法执行此操作:

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

System.Console.WriteLine(conString);

或者使用DI的结构化类:

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:

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中使用它:

"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

在 .NET Core 6 中

应用程序设置.json

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

程序.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 4

我就是这样做的：

我在 appsettings.json 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 中，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，无论您需要连接字符串，您都可以这样调用它：

SqlHelper.GetConnection();

Answer 5

有关详细信息,请参阅链接: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#Startup.cs

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

Answer 6

我发现解决此问题的方法是在启动时在构建器中使用AddJsonFile（这使它可以找到存储在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();
    }

然后我可以将配置字符串设置如下：

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

这是在dotnet core 1.1上

Answer 7

ASP.NET Core（在我的例子中是3.1）为我们提供了到 Controllers 的构造函数注入，所以你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"
        }
}