Necromancing。 当搜索任何。net框架的解决方案时，这个页面是第一个搜索结果，所以这里作为一个公共服务，它是如何在EntityFrameworkCore(用于。net Core 1和2)中完成的:

var someQuery = (
    from projects in _context.projects
    join issues in _context.issues on projects.Id equals issues.ProjectId into tmpMapp
    from issues in tmpMapp.DefaultIfEmpty()
    select issues
) //.ToList()
;

// string sql = someQuery.ToString();
// string sql = Microsoft.EntityFrameworkCore.IQueryableExtensions.ToSql(someQuery);
// string sql = Microsoft.EntityFrameworkCore.IQueryableExtensions1.ToSql(someQuery);
// using Microsoft.EntityFrameworkCore;
string sql = someQuery.ToSql();
System.Console.WriteLine(sql);

然后这些扩展方法(IQueryableExtensions1用于。net Core 1.0, IQueryableExtensions用于。net Core 2.0):

using System;
using System.Linq;
using System.Reflection;
using Microsoft.EntityFrameworkCore.Internal;
using Microsoft.EntityFrameworkCore.Query;
using Microsoft.EntityFrameworkCore.Query.Internal;
using Microsoft.EntityFrameworkCore.Storage;
using Remotion.Linq.Parsing.Structure;


namespace Microsoft.EntityFrameworkCore
{

    // https://stackoverflow.com/questions/1412863/how-do-i-view-the-sql-generated-by-the-entity-framework
    // http://rion.io/2016/10/19/accessing-entity-framework-core-queries-behind-the-scenes-in-asp-net-core/

    public static class IQueryableExtensions
    {
        private static readonly TypeInfo QueryCompilerTypeInfo = typeof(QueryCompiler).GetTypeInfo();

        private static readonly FieldInfo QueryCompilerField = typeof(EntityQueryProvider).GetTypeInfo().DeclaredFields
            .First(x => x.Name == "_queryCompiler");

        private static readonly PropertyInfo NodeTypeProviderField =
            QueryCompilerTypeInfo.DeclaredProperties.Single(x => x.Name == "NodeTypeProvider");

        private static readonly MethodInfo CreateQueryParserMethod =
            QueryCompilerTypeInfo.DeclaredMethods.First(x => x.Name == "CreateQueryParser");

        private static readonly FieldInfo DataBaseField =
            QueryCompilerTypeInfo.DeclaredFields.Single(x => x.Name == "_database");

        private static readonly PropertyInfo DatabaseDependenciesField =
            typeof(Database).GetTypeInfo().DeclaredProperties.Single(x => x.Name == "Dependencies");

        public static string ToSql<TEntity>(this IQueryable<TEntity> query) where TEntity : class
        {
            if (!(query is EntityQueryable<TEntity>) && !(query is InternalDbSet<TEntity>))
            {
                throw new ArgumentException("Invalid query");
            }

            var queryCompiler = (QueryCompiler) QueryCompilerField.GetValue(query.Provider);
            var nodeTypeProvider = (INodeTypeProvider) NodeTypeProviderField.GetValue(queryCompiler);
            var parser = (IQueryParser) CreateQueryParserMethod.Invoke(queryCompiler, new object[] {nodeTypeProvider});
            var queryModel = parser.GetParsedQuery(query.Expression);
            var database = DataBaseField.GetValue(queryCompiler);
            var databaseDependencies = (DatabaseDependencies) DatabaseDependenciesField.GetValue(database);
            var queryCompilationContext = databaseDependencies.QueryCompilationContextFactory.Create(false);
            var modelVisitor = (RelationalQueryModelVisitor) queryCompilationContext.CreateQueryModelVisitor();
            modelVisitor.CreateQueryExecutor<TEntity>(queryModel);
            var sql = modelVisitor.Queries.First().ToString();

            return sql;
        }
    }



    public class IQueryableExtensions1
    {
        private static readonly TypeInfo QueryCompilerTypeInfo = typeof(QueryCompiler).GetTypeInfo();

        private static readonly FieldInfo QueryCompilerField = typeof(EntityQueryProvider).GetTypeInfo()
            .DeclaredFields
            .First(x => x.Name == "_queryCompiler");

        private static readonly PropertyInfo NodeTypeProviderField =
            QueryCompilerTypeInfo.DeclaredProperties.Single(x => x.Name == "NodeTypeProvider");

        private static readonly MethodInfo CreateQueryParserMethod =
            QueryCompilerTypeInfo.DeclaredMethods.First(x => x.Name == "CreateQueryParser");

        private static readonly FieldInfo DataBaseField =
            QueryCompilerTypeInfo.DeclaredFields.Single(x => x.Name == "_database");

        private static readonly FieldInfo QueryCompilationContextFactoryField = typeof(Database).GetTypeInfo()
            .DeclaredFields.Single(x => x.Name == "_queryCompilationContextFactory");


        public static string ToSql<TEntity>(IQueryable<TEntity> query) where TEntity : class
        {
            if (!(query is EntityQueryable<TEntity>) && !(query is InternalDbSet<TEntity>))
            {
                throw new ArgumentException("Invalid query");
            }

            var queryCompiler = (IQueryCompiler) QueryCompilerField.GetValue(query.Provider);

            var nodeTypeProvider = (INodeTypeProvider) NodeTypeProviderField.GetValue(queryCompiler);
            var parser =
                (IQueryParser) CreateQueryParserMethod.Invoke(queryCompiler, new object[] {nodeTypeProvider});
            var queryModel = parser.GetParsedQuery(query.Expression);
            var database = DataBaseField.GetValue(queryCompiler);
            var queryCompilationContextFactory =
                (IQueryCompilationContextFactory) QueryCompilationContextFactoryField.GetValue(database);
            var queryCompilationContext = queryCompilationContextFactory.Create(false);
            var modelVisitor = (RelationalQueryModelVisitor) queryCompilationContext.CreateQueryModelVisitor();
            modelVisitor.CreateQueryExecutor<TEntity>(queryModel);
            var sql = modelVisitor.Queries.First().ToString();

            return sql;
        }


    }


}

我刚刚做了这个:

IQueryable<Product> query = EntitySet.Where(p => p.Id == id);
Debug.WriteLine(query);

结果显示在Output:

SELECT 
    [Extent1].[Id] AS [Id], 
    [Extent1].[Code] AS [Code], 
    [Extent1].[Name] AS [Name], 
    [Extent2].[Id] AS [Id1], 
    [Extent2].[FileName] AS [FileName], 
    FROM  [dbo].[Products] AS [Extent1]
    INNER JOIN [dbo].[PersistedFiles] AS [Extent2] ON [Extent1].[PersistedFileId] = [Extent2].[Id]
    WHERE [Extent1].[Id] = @p__linq__0

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。

我正在做集成测试，需要在实体框架核心2.1中调试生成的SQL语句，所以我使用DebugLoggerProvider或ConsoleLoggerProvider，如下所示:

[Fact]
public async Task MyAwesomeTest
    {
        //setup log to debug sql queries
        var loggerFactory = new LoggerFactory();
        loggerFactory.AddProvider(new DebugLoggerProvider());
        loggerFactory.AddProvider(new ConsoleLoggerProvider(new ConsoleLoggerSettings()));

        var builder = new DbContextOptionsBuilder<DbContext>();
        builder
            .UseSqlServer("my connection string") //"Server=.;Initial Catalog=TestDb;Integrated Security=True"
            .UseLoggerFactory(loggerFactory);

        var dbContext = new DbContext(builder.Options);

        ........

下面是Visual Studio控制台的输出示例:

您可以执行以下操作:

IQueryable query = from x in appEntities
             where x.id == 32
             select x;

var sql = ((System.Data.Objects.ObjectQuery)query).ToTraceString();

或EF6:

var sql = ((System.Data.Entity.Core.Objects.ObjectQuery)query)
            .ToTraceString();

或EF6.3+:

var sql = ((dynamic)flooringStoresProducts).Sql;

这将为您提供生成的SQL。

对于那些使用Entity Framework 6及以上版本的用户，如果你想在Visual Studio中查看输出SQL(就像我做的那样)，你必须使用新的日志/拦截功能。

添加下面这行代码将在Visual Studio输出面板中输出生成的SQL(以及其他与执行相关的详细信息):

using (MyDatabaseEntities context = new MyDatabaseEntities())
{
    context.Database.Log = s => System.Diagnostics.Debug.WriteLine(s);
    // query the database using EF here.
}

有关登录EF6的更多信息，请参阅这个漂亮的博客系列:http://blog.oneunicorn.com/2013/05/08/ef6-sql-logging-part-1-simple-logging/

注意:确保在DEBUG模式下运行项目。