两种查看EFCore生成Sql语句的方法

一.利用反射生成查询语句

该方法转载自：https://jhrs.com/2019/28488.html (略有修改)

using Microsoft.EntityFrameworkCore.Query;
using Microsoft.EntityFrameworkCore.Query.Internal;
using Microsoft.EntityFrameworkCore.Storage;
using System.Linq;
using System.Reflection;

namespace Common.Standard.EFCore
{
    public static class QueryableExtensions
    {
        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 FieldInfo QueryModelGeneratorField = typeof(QueryCompiler).GetTypeInfo().DeclaredFields.First(x => x.Name == "_queryModelGenerator");
        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");

        /// <summary>
        /// 获取本次查询SQL语句
        /// </summary>
        /// <typeparam name="TEntity"></typeparam>
        /// <param name="query"></param>
        /// <returns></returns>
        public static string ToSql<TEntity>(this IQueryable<TEntity> query)
        {
            var queryCompiler = (QueryCompiler)QueryCompilerField.GetValue(query.Provider);
            var queryModelGenerator = (QueryModelGenerator)QueryModelGeneratorField.GetValue(queryCompiler);
            var queryModel = queryModelGenerator.ParseQuery(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;
        }
    }
}

使用方法

var ss = _context.UserTable.Where(m => m.UserName == "admin");
string sql = ss.ToSql();

效果

备注：该扩展貌似只能应用于EF查询方法，我尝试过各种重写方法，仍然不能完美的生成真实执行的Sql语句，如果哪位高人有办法做到请在评论区指导一下。

二、Microsoft.Extensions.Logging.Debug在控制台输出完整调试日志

这种方法是比较推荐的，可以完整的输出EF生成的SQL语句

1.用NuGet管理器添加包: Microsoft.Extensions.Logging.Debug

2.修改DbContext类

public partial class MyDbnContext : DbContext
{
        [Obsolete]
        public static readonly LoggerFactory LoggerFactory = new LoggerFactory(new[] { new DebugLoggerProvider((_, __) => true) });

... ...

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            base.OnConfiguring(optionsBuilder);
            optionsBuilder.UseLoggerFactory(LoggerFactory);
        }

... ...
}

3.在想要查看sql的db.SaveChanges()方法上加断点，然后调试程序。

4.点击VisualStudio工具条：调试->窗口->输出，打开输出日志，并搜索EntityFrameworkCore,结果如下

红框内圈出的就是完整的SQL输出

参考项目：https://github.com/FB208/CodeSpace/blob/master/CodeSpace.CSharp/WebMvc.Model/WebMvc.Model/BBSAdmin/BBSAdminContext.cs