【发布时间】：2021-01-09 18:29:45
【问题描述】：
我创建了一个 .Net Core 3.1 控制台应用程序，并尝试使用 EntityFramework 来处理我的 Oracle 数据库。我找到了几个关于这个主题的视频和文章，但它们都涉及 HTTP 应用程序，而不是控制台应用程序。
我使用 powershell 命令搭建了表格并创建了一个名为 ModelContext 的 DbContext。在我的 Program.cs 中，我有一个 Host.CreateDefaultBuilder 并添加了 services.AddDbContext 并将连接字符串放在我的 appsettings.json 文件中。
我的问题是，当它尝试将上下文添加到主机中的服务时，我无法将连接字符串从 appsettings 中拉出。我在 Configuration.GetConnectionString 上收到设计时错误，说 “Configuration does not contain a definition for ‘GetConnectionString’”。
我通过 NuGet 安装了System.Configuration.ConfigurationManager，并在我的 Program.cs 文件中添加了using System.Configuration。
如何从主机构建器中的 appsettings 获取连接字符串？
程序.cs
var host = Host.CreateDefaultBuilder().ConfigureServices((context, services) =>
{
services.AddTransient<IAppHost, AppHost>();
services.AddTransient<IFileManager, FileManager>();
services.AddTransient<IDataManager, DataManager>();
var connstring = Configuration.GetConnectionString("DbConnection");
services.AddDbContext<ModelContext>(options =>
{
options.UseOracle(connstring);
});
services.AddLogging(builder =>
{
builder.AddNLog("nlog.config");
});
}).Build();
更新代码
这是我的 Program.cs 文件中的所有代码。不幸的是，不确定我做了什么导致此问题，但现在我的 FileManger 类出现错误。
Unable to resolve service for type 'Microsoft.Extensions.Logging.Logger`1[EmailUpdateExport.FileManager]' while attempting to activate 'EmailUpdateExport.FileManager'.
我什至取消了从刚刚添加的 appsettings 中获取 DbConnection 的代码，但仍然出现错误。
class Program
{
static void Main(string[] args)
{
//Calls the Builder so that you can get to the appsettings.
var builder = new ConfigurationBuilder();
BuildConfig(builder);
var logger = NLog.Web.NLogBuilder.ConfigureNLog("nlog.config").GetCurrentClassLogger();
try
{
logger.Debug("Initializing Program.Main");
var host = Host.CreateDefaultBuilder()
.ConfigureAppConfiguration((hostingContext, config) =>
{
config.SetBasePath(Path.Combine(AppContext.BaseDirectory));
config.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true);
})
.ConfigureServices((context, services) =>
{
services.AddTransient<IAppHost, AppHost>();
services.AddTransient<IFileManager, FileManager>();
services.AddTransient<IDataManager, DataManager>();
var connstring = context.Configuration["ConnectionStrings:DbConnection"];
services.AddDbContext<ModelContext>(options =>
{
options.UseOracle(connstring);
});
services.AddLogging(builder =>
{
builder.AddNLog("nlog.config");
});
}).Build();
//Create instance of AppHost and call the Run() function to run the business logic.
var svc = ActivatorUtilities.CreateInstance<AppHost>(host.Services);
svc.Run();
}
catch (Exception ex)
{
//NLog: catch setup errors
logger.Error("Stopped program setup with Error. {0} | {1} | {2}", ex.Message, ex.StackTrace, ex.InnerException);
throw;
}
finally
{
// Ensure to flush and stop internal timers/threads before application-exit
NLog.LogManager.Shutdown();
}
}
static void BuildConfig(IConfigurationBuilder builder)
{
//Sets up the ability to talk to the appsettings.json
builder.SetBasePath(Directory.GetCurrentDirectory())
.AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
.AddJsonFile($"appsettings.{Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT") ?? "Production"}.json", optional: true)
.AddEnvironmentVariables();
}
}
这是我的文件管理器，以防有人对此提出建议。
public class FileManager : IFileManager
{
private readonly ILogger<FileManager> _log;
private readonly IConfiguration _configuration;
public FileManager(Logger<FileManager> log, IConfiguration config)
{
_log = log;
_configuration = config;
}
public void CreateFileDirectory(string FilePath)
{
try
{
//create the target location if it doesn't exist
if (!Directory.Exists(FilePath))
{
_log.LogInformation("Create directory: " + FilePath);
Directory.CreateDirectory(FilePath);
}
}
catch (Exception ex)
{
_log.LogError("Error creating Export directory. {0} | {1} | {2} ", ex.Message, ex.StackTrace, ex.InnerException);
}
}
public void CopyFile(string sourceLocation, string destinationLocation, string fileName)
{
_log.LogInformation("Source location: {0} | Destination location: {1} | File Name: {2}", sourceLocation, destinationLocation, fileName);
var sourceFile = Path.Combine(sourceLocation, fileName);
var destinationFile = Path.Combine(destinationLocation, fileName);
_log.LogInformation("SourceFilePath: {0}", sourceFile);
_log.LogInformation("DestinationFilePath: {0}", destinationFile);
try
{
//check to make sure source exists first
if (File.Exists(sourceFile))
{
//get rid of the file if it already exists. Shouldn't be an issue most to the time.
if (File.Exists(destinationFile))
{
File.Delete(destinationFile);
}
File.Copy(sourceFile, destinationFile);
}
else
_log.LogInformation("Source file does not exist. File: {0}", sourceFile);
}
catch (Exception ex)
{
_log.LogError("Error copying file. Source: {0} | Destination: {1}. {2} | {3} | {4}", sourceFile, destinationFile, ex.Message, ex.StackTrace, ex.InnerException);
throw;
}
}
【问题讨论】：
-
请显示您添加/构建
Configuration的代码。 -
看看这个，网上还有很多其他的例子。 garywoodfine.com/configuration-api-net-core-console-application
-
谢谢，我会看看那篇文章，看看是否可以将它合并到我的代码中。
-
@RomanDoskoch 配置来自 NuGet 包“System.Configuration.ConfigurationManager”中的“使用 System.Configuration”。
-
你为什么使用 System.Configuration.ConfigurationManager？这适用于 app.config 和 web.config，而不是 appsettings.json。
标签： c# asp.net-core .net-core dependency-injection