Access SQL queries Generated By Entity Framework Core 3

Create a class EntityFrameworkSqlLogger.cs

using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using Microsoft.Extensions.Logging;

namespace MyApp.Logging
{
    /// <summary>
    /// ILogger implementation
    /// </summary>
    public class EntityFrameworkSqlLogger : ILogger
    {
        #region Fields
        Action<EntityFrameworkSqlLogMessage> _logMessage;
        #endregion

        #region Constructor
        public EntityFrameworkSqlLogger(Action<EntityFrameworkSqlLogMessage> logMessage)
        {
            _logMessage = logMessage;
        }
        #endregion

        #region Implementation
        public IDisposable BeginScope<TState>(TState state)
        {
            return default;
        }

        public bool IsEnabled(LogLevel logLevel)
        {
            return true;
        }

        public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception exception, Func<TState, Exception, string> formatter)
        {
            if (eventId.Id != 20101)
            {
                //Filter messages that aren't relevant.
                //There may be other types of messages that are relevant for other database platforms...

                return;
            }

            if (state is IReadOnlyList<KeyValuePair<string, object>> keyValuePairList)
            {
                var entityFrameworkSqlLogMessage = new EntityFrameworkSqlLogMessage
                (
                    eventId,
                    (string)keyValuePairList.FirstOrDefault(k => k.Key == "commandText").Value,
                    (string)keyValuePairList.FirstOrDefault(k => k.Key == "parameters").Value,
                    (CommandType)keyValuePairList.FirstOrDefault(k => k.Key == "commandType").Value,
                    (int)keyValuePairList.FirstOrDefault(k => k.Key == "commandTimeout").Value,
                    (string)keyValuePairList.FirstOrDefault(k => k.Key == "elapsed").Value
                );

                _logMessage(entityFrameworkSqlLogMessage);
            }
        }
        #endregion
    }
    
    /// <summary>
    /// Data model
    /// </summary>
    public class EntityFrameworkSqlLogMessage
    {
        public EntityFrameworkSqlLogMessage(
            EventId eventId,
            string commandText,
            string parameters,
            CommandType commandType,
            int commandTimeout,
            string elapsed
        )
        {
            EventId = eventId;
            CommandText = commandText;
            Parameters = parameters;
            CommandType = commandType;
            Elapsed = elapsed;
            CommandTimeout = commandTimeout;
        }

        public string Elapsed { get; }
        public int CommandTimeout { get; }
        public EventId EventId { get; }
        public string CommandText { get; }
        public string Parameters { get; }
        public CommandType CommandType { get; }
    }
    
    /// <summary>
    /// ILogger provider
    /// </summary>
    public class SingletonLoggerProvider : ILoggerProvider
    {
        #region Fields
        ILogger _logger;
        #endregion

        #region Constructor
        public SingletonLoggerProvider(ILogger logger)
        {
            _logger = logger;
        }
        #endregion

        #region Implementation
        public ILogger CreateLogger(string categoryName)
        {
            return _logger;
        }

        public void Dispose()
        {
        }
        #endregion
    }
}

Add Logger to DbContext OnConfiguring Met

public class CartServiceDbContext : DbContext
{
...

  protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
  {
      var entityFrameworkSqlLogger = new EntityFrameworkSqlLogger((m) =>
      {
          System.Console.WriteLine($"SQL Query:\r\n{m.CommandText}\r\nElapsed:{m.Elapsed} millisecods\r\n\r\n");
      });

      var myLoggerFactory = LoggerFactory.Create(builder =>
      {
          builder
              .AddFilter((category, level) =>
                  category == DbLoggerCategory.Database.Command.Name
                  && level == LogLevel.Information);
      });

      myLoggerFactory.AddProvider(new SingletonLoggerProvider(entityFrameworkSqlLogger));
      optionsBuilder.UseLoggerFactory(myLoggerFactory);
      DbConnectorUtils.ConfigureOptionsBuilder(optionsBuilder);
  }

...
}

References

Existing SQL Server

Generating a model from an existing database .Net Core 2.0

In a folder that will contain your demo project type the following command:
dotnet new console for a console application or dotnet new mvc for a MVC or Web API application

Add the Entity Framework Core and Tools packages to the project:
This is the EF Core provider for SQL Server.
dotnet add package Microsoft.EntityFrameworkCore.SqlServer

This package contains the Entity Framework Core commands. Both of these packages are required for any Entity Framework Core application that targets SQL Server.
dotnet add package Microsoft.EntityFrameworkCore.Tools

The final package is required for supporting the scaffolding of the model.
dotnet add package Microsoft.EntityFrameworkCore.SqlServer.Design

Test if Entity Framework is available
dotnet ef -h

Now use the DbContext Scaffold command to generate the model passing two arguments:

  • a connection string
  • a provider

dotnet ef dbcontext scaffold "Server=.\;Database=AdventureWorks;Trusted_Connection=True;" Microsoft.EntityFrameworkCore.SqlServer -o Models

dotnet ef dbcontext scaffold "Server=localhost,1433\\Catalog=AdventureWorks;Database=AdventureWorks;User=SA;Password=;" Microsoft.EntityFrameworkCore.SqlServer -o Models

Once you have executed the command, you will see that a folder named Models has been created in the project folder, containing a collection of class files representing the entities.
You can find also a class file containing the DbContext class.
The DbContext class will take the name of the database plus “Context”.
You can override this using the -c or –context option e.g.
dotnet ef dbcontext scaffold "Server=.\;Database=AdventureWorksLT2012;Trusted_Connection=True;" Microsoft.EntityFrameworkCore.SqlServer -o Models -c "AdventureContext"