适用于EF 6.0及以上: 对于那些想要了解更多关于日志功能并添加到已经给出的一些答案的人。

现在可以记录从EF发送到数据库的任何命令。查看从EF 6生成的查询。x，使用DBContext.Database.Log属性

记录什么

- SQL for all different kinds of commands. For example: - Queries, including normal LINQ queries, eSQL queries, and raw queries from methods such as SqlQuery. - Inserts, updates, and deletes generated as part of SaveChanges - Relationship loading queries such as those generated by lazy loading - Parameters - Whether or not the command is being executed asynchronously - A timestamp indicating when the command started executing - Whether or not the command completed successfully, failed by throwing an exception, or, for async, was canceled - Some indication of the result value - The approximate amount of time it took to execute the command. Note that this is the time from sending the command to getting the result object back. It does not include time to read the results.

例子:

using (var context = new BlogContext()) 
{ 
    context.Database.Log = Console.Write; 

    var blog = context.Blogs.First(b => b.Title == "One Unicorn"); 

    blog.Posts.First().Title = "Green Eggs and Ham"; 

    blog.Posts.Add(new Post { Title = "I do not like them!" }); 

    context.SaveChangesAsync().Wait(); 
}

输出:

SELECT TOP (1)
    [Extent1].[Id] AS [Id],
    [Extent1].[Title] AS [Title]
    FROM [dbo].[Blogs] AS [Extent1]
    WHERE (N'One Unicorn' = [Extent1].[Title]) AND ([Extent1].[Title] IS NOT NULL)
-- Executing at 10/8/2013 10:55:41 AM -07:00
-- Completed in 4 ms with result: SqlDataReader

SELECT
    [Extent1].[Id] AS [Id],
    [Extent1].[Title] AS [Title],
    [Extent1].[BlogId] AS [BlogId]
    FROM [dbo].[Posts] AS [Extent1]
    WHERE [Extent1].[BlogId] = @EntityKeyValue1
-- EntityKeyValue1: '1' (Type = Int32)
-- Executing at 10/8/2013 10:55:41 AM -07:00
-- Completed in 2 ms with result: SqlDataReader

UPDATE [dbo].[Posts]
SET [Title] = @0
WHERE ([Id] = @1)
-- @0: 'Green Eggs and Ham' (Type = String, Size = -1)
-- @1: '1' (Type = Int32)
-- Executing asynchronously at 10/8/2013 10:55:41 AM -07:00
-- Completed in 12 ms with result: 1

INSERT [dbo].[Posts]([Title], [BlogId])
VALUES (@0, @1)
SELECT [Id]
FROM [dbo].[Posts]
WHERE @@ROWCOUNT > 0 AND [Id] = scope_identity()
-- @0: 'I do not like them!' (Type = String, Size = -1)
-- @1: '1' (Type = Int32)
-- Executing asynchronously at 10/8/2013 10:55:41 AM -07:00
-- Completed in 2 ms with result: SqlDataReader

记录到外部文件:

using (var context = new BlogContext()) 
{  
    using (var sqlLogFile = new StreamWriter("C:\\temp\\LogFile.txt"))
    {          
         context.Database.Log = sqlLogFile.Write;     
         var blog = context.Blogs.First(b => b.Title == "One Unicorn"); 
         blog.Posts.First().Title = "Green Eggs and Ham"; 
         context.SaveChanges();
   }
}

更多信息在这里:记录和拦截数据库操作

IQueryable query = from x in appEntities
                   where x.id = 32
                   select x;
var queryString = query.ToString();

将返回sql查询。使用EntityFramework的数据上下文进行工作

从EF6.1开始，您可以使用拦截器来注册数据库记录器。 请参见“拦截器”和“记录数据库操作”章节

<configuration>
  <entityFramework>
    <interceptors> 
      <interceptor type="System.Data.Entity.Infrastructure.Interception.DatabaseLogger, EntityFramework"> 
        <parameters> 
          <parameter value="C:\Temp\LogOutput.txt"/> 
          <parameter value="true" type="System.Boolean"/> 
        </parameters> 
      </interceptor> 
    </interceptors>
  </entityFramework>
</configuration>

我的答案是针对EF core的。我参考了这个github问题，以及配置DbContext的文档:

简单的

重写DbContext类(YourCustomDbContext)的onconfiguration方法，如下所示使用ConsoleLoggerProvider;你的查询应该记录到控制台:

public class YourCustomDbContext : DbContext
{
    #region DefineLoggerFactory
    public static readonly LoggerFactory MyLoggerFactory
        = new LoggerFactory(new[] {new ConsoleLoggerProvider((_, __) => true, true)});
    #endregion


    #region RegisterLoggerFactory
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        => optionsBuilder
            .UseLoggerFactory(MyLoggerFactory); // Warning: Do not create a new ILoggerFactory instance each time                
    #endregion
}

复杂的

这个Complex case避免覆盖DbContext onconfiguration方法。，这在文档中是不鼓励的:“这种方法不适合测试，除非测试的目标是整个数据库。”

这个复杂的案例使用:

启动类ConfigureServices方法中的IServiceCollection (而不是重写onconfiguration方法;好处是DbContext和你想要使用的ILoggerProvider之间的耦合更松散) ILoggerProvider的实现(而不是使用上面所示的ConsoleLoggerProvider实现;好处是我们的实现展示了我们如何将日志记录到文件(我没有看到一个文件日志记录提供程序与EF核心))

是这样的:

public class Startup

    public void ConfigureServices(IServiceCollection services)
    {
        ...
        var lf = new LoggerFactory();
        lf.AddProvider(new MyLoggerProvider());

        services.AddDbContext<YOUR_DB_CONTEXT>(optionsBuilder => optionsBuilder
                .UseSqlServer(connection_string)
                //Using the LoggerFactory 
                .UseLoggerFactory(lf));
        ...
    }
}

这里是MyLoggerProvider的实现(以及它的MyLogger，它将其日志附加到您可以配置的文件中;您的EF Core查询将出现在文件中。)

public class MyLoggerProvider : ILoggerProvider
{
    public ILogger CreateLogger(string categoryName)
    {
        return new MyLogger();
    }

    public void Dispose()
    { }

    private class MyLogger : ILogger
    {
        public bool IsEnabled(LogLevel logLevel)
        {
            return true;
        }

        public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception exception, Func<TState, Exception, string> formatter)
        {
            File.AppendAllText(@"C:\temp\log.txt", formatter(state, exception));
            Console.WriteLine(formatter(state, exception));
        }

        public IDisposable BeginScope<TState>(TState state)
        {
            return null;
        }
    } 
}

好吧，目前我正在使用Express分析器，缺点是它只适用于MS SQL Server。你可以在这里找到这个工具:https://expressprofiler.codeplex.com/

在不更改代码的情况下，使查询始终方便 将它添加到你的DbContext中，并在visual studio的输出窗口中检查它。

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        Database.Log = (query)=> Debug.Write(query);
    }

类似于@Matt Nibecker的答案，但有了这个答案，你不必每次需要查询时都将它添加到当前代码中。