在开发中，我们想在调试中查看EF Core执行的sql语句，可以使用SQL Studio Manager Tools工具，另一种方式是使用EF Core提供的日志。在ASP.NET Core使用Entity Framework Core的日志.

早在Entity Framework Core1.0 ,使用相关的ILoggerProvider ILogger 这些基础接口类.来实现过日志记录.

在Entity Framework Core2.0  估计是为了配合ASP.NET Core的日志.所以对这些接口进行了更进一步的包装,也弃用了一些接口和类,如:IRelationalCommandBuilderFactory ,DbCommandLogData 但是Entity Framework Core2.0 在DbContextOptionsBuilder添加了新的扩展方法.UseLoggerFactory 看到LoggerFactory,研究过ASP.NET Core日志记录的,应该就很熟悉了..这是ASP.NET Core日志记录的工厂类. 也就是为什么我们如果在ASP.NET Core中注入自己的日志记录,也可以通过配置来记录相关的SQL操作的原因. 这里我们主要是直接只监控EF Core的日志.

using dotNET.Core;using Microsoft.Extensions.Logging;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Text;namespace dotNET.EFCoreRepository
{/// <summary>/// ef 日志/// </summary>public class EFLoggerProvider : ILoggerProvider{public ILogger CreateLogger(string categoryName) => new EFLogger(categoryName);public void Dispose() { }}/// <summary>/// /// </summary>public class EFLogger : ILogger{private readonly string categoryName;public EFLogger(string categoryName) => this.categoryName = categoryName;public bool IsEnabled(LogLevel logLevel) => true;public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception exception, Func<TState, Exception, string> formatter){//ef core执行数据库查询时的categoryName为Microsoft.EntityFrameworkCore.Database.Command,日志级别为Informationif (categoryName == "Microsoft.EntityFrameworkCore.Database.Command"&& logLevel == LogLevel.Information){var logContent = formatter(state, exception);NLogger.Debug(logContent);//TraceMessage("Something happened.");//  NLogger.Info(GetCodeLineAndFileName());//TODO: 拿到日志内容想怎么玩就怎么玩吧Console.WriteLine();Console.ForegroundColor = ConsoleColor.Green;Console.WriteLine(logContent);Console.ResetColor();}}public IDisposable BeginScope<TState>(TState state) => null;public void TraceMessage(string message,[System.Runtime.CompilerServices.CallerMemberName] string memberName = "",[System.Runtime.CompilerServices.CallerFilePath] string sourceFilePath = "",[System.Runtime.CompilerServices.CallerLineNumber] int sourceLineNumber = 0
){NLogger.Debug("message: " + message);NLogger.Debug("member name: " + memberName);NLogger.Debug("source file path: " + sourceFilePath);NLogger.Debug("source line number: " + sourceLineNumber);}public string GetCodeLineAndFileName(){StackTrace insStackTrace = new StackTrace(true);var insStackFrames = insStackTrace.GetFrames();string str = "";foreach(var insStackFrame in insStackFrames){str += String.Format("\nFile: {0}, Line: {1}\n", insStackFrame.GetFileName(), insStackFrame.GetFileLineNumber());}return str;}}
}

第一步：添加日志类

第二步：OnConfiguring  方法添加日志调用

protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder){var loggerFactory = new LoggerFactory();loggerFactory.AddProvider(new EFLoggerProvider());optionsBuilder.UseLoggerFactory(loggerFactory);base.OnConfiguring(optionsBuilder);}