如何在应用程序创建数据库之前保存 Serilog 事件日志？

Question

I created a logger successfully using Serilog but I can't determine how to tell if the SQL Server database I'm logging to exists before I create the logger. The goal is to create the logger before this line in my Main function so I get all of the startup logs:

var host = CreateHostBuilder(args).Build();

However, if I do that, and the database doesn't exist yet, the logging table won't get created the first time I start the application. It will get created the second time I start the application because I'm creating and seeding the database after that line of code.

I want to create the logger before CreateHostBuilder runs if the database exists or create the logger after CreateHostBuilder and SeedDatabase run if the database doesn't exist yet. I can't run CreateLogger() twice either or I'll get an exception.

Here is the code:

public static void Main(string[] args)
{
    try
    {
        // If I create the logger here I'll see all the startup logs
        // if the database exists. If the database doesn't exist yet the 
        // logging table won't get created until the second time I startup the app.
        CreateLogger();

        Log.Information("Starting Up");

        var host = CreateHostBuilder(args).Build();

        SeedDatabase(host);

        // If I create the logger here I don't get all of the startup logs but
        // it ensures that if the database hasn't been created and seeded yet the 
        // logging table is still created.
        CreateLogger();

        host.Run();
    }
    catch (Exception exception)
    {
        Log.Fatal(exception, "Application start-up failed");
    }
    finally
    {
        Log.CloseAndFlush();
    }
}

public static void CreateLogger()
{
    Log.Logger = new LoggerConfiguration()
        // Add/Update configuration settings in appsettings.json.
        // Don't add them here.
        .ReadFrom.Configuration(Configuration)
        .Enrich.FromLogContext()
        .CreateLogger();
}

UPDATED appsettings.json after adding file logging:

"Serilog": {
    "MinimumLevel": "Information",
    "WriteTo": [
      {
        "Name": "MSSqlServer",
        "Args": {
          "connectionString": "DbContext",
          "tableName": "EventLog",
          "autoCreateSqlTable": true
        }
      }
    ],
    "WriteTo:Async": {
      "Name": "Async",
      "Args": {
        "configure": [
          {
            "Name": "File",
            "Args": {
              "path": "../../EventLogs/",
              "rollingInterval": "Day"
            }
          }
        ]
      }
    }
  }

Answer 1

在 CreateLogger 中做一些回退逻辑，如果数据库不存在，它会登录到文件中，并且在创建 db 后，如果需要创建它，您可以将这些日志文件内容写入 db。