实体框架核心3.x

Question

我正在使用 ~~Entity Framework 7 Core RC2~~ （重命名为：EF Core），我需要查看正在生成哪个SQL代码。在先前版本的Entity Framework中，我可以使用以下内容：

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

其中query是IQueryable对象......但是EF Core中没有ToTraceString。

我如何在EF Core中做类似的事情？

Answer 1

由于EF 7被重命名为Entity Framework Core，我将总结EF Core的选项。

从IQueryable<>记录SQL语句有三种方法：

使用内置或自定义日志记录。使用您选择的记录器或.NET核心中的内置Logger记录执行查询，如this tutorial中所述。
使用 Profiler 。使用像MiniProfiler这样的SQL事件探查器来监视正在执行的查询。
使用疯狂反思代码。您可以实现一些类似于旧方法的自定义反射代码来执行相同的基本概念。

这是疯狂的反射代码（扩展方法）：

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 FieldInfo QueryModelGeneratorField = QueryCompilerTypeInfo.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");

    public static string ToSql<TEntity>(this IQueryable<TEntity> query) where TEntity : class
    {
        var queryCompiler = (QueryCompiler)QueryCompilerField.GetValue(query.Provider);
        var modelGenerator = (QueryModelGenerator)QueryModelGeneratorField.GetValue(queryCompiler);
        var queryModel = modelGenerator.ParseQuery(query.Expression);
        var database = (IDatabase)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;
    }
}

将此扩展方法添加到代码后，您可以按如下方式使用该方法：

// Build a query using Entity Framework
var query = _context.Widgets.Where(w => w.IsReal && w.Id == 42);  
// Get the generated SQL
var sql = query.ToSql();

推介：http://rion.io/2016/10/19/accessing-entity-framework-core-queries-behind-the-scenes-in-asp-net-core/和https://gist.github.com/rionmonster/2c59f449e67edf8cd6164e9fe66c545a

更新：已修改，以便支持EF Core 2.1

Answer 2

对于EF Core 2.1.2，您可以使用它。

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");

    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;
    }
}

Answer 3

对于只想诊断一次点火失败的EF Core查询等而不希望更改其代码的任何人，那么如果您安装了SQL Server Management Studio（SSMS），则可以fire up the SQL Profiler从SSMS的“工具”菜单中：

然后打开打开的SQL Profiler中运行的新跟踪。

然后，您将能够看到来自EF的传入SQL请求，它们通常结构良好且易于阅读。

Answer 4

实体框架核心3.x

您可以通过记录获取它。

创建工厂：

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

告诉DbContext使用哪个工厂：

optionsBuilder.UseLoggerFactory(_loggerFactory);

来自this post

如果要实现ILogger，可以获取更多信息：

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
}

Answer 5

对于带有变量的EF Core 3.1，我有以下内容（基于某些GitHub comments from halllo），这些内容已在@ Thom Kiesewetter等人的评论中链接到上面。

/// <summary>
/// SQL Extension methods to get the SQL and check correctness
/// Class can be removed with EF Core 5 (https://github.com/dotnet/efcore/issues/6482#issuecomment-587605366) (although maybe variable substitution might still be necessary if we want them inline)
/// </summary>
public static class SqlExtensions
{
    private static object Private(this object obj, string privateField) => obj?.GetType().GetField(privateField, BindingFlags.Instance | BindingFlags.NonPublic)?.GetValue(obj);
    private static T Private<T>(this object obj, string privateField) => (T)obj?.GetType().GetField(privateField, BindingFlags.Instance | BindingFlags.NonPublic)?.GetValue(obj);

    /// <summary>
    /// Gets a SQL statement from an IQueryable
    /// </summary>
    /// <param name="query">The query to get the SQL statement for</param>
    /// <returns>Formatted SQL statement as a string</returns>
    public static string ToQueryString<TEntity>(this IQueryable<TEntity> query) where TEntity : class
    {
        using var enumerator = query.Provider.Execute<IEnumerable<TEntity>>(query.Expression).GetEnumerator();
        var relationalCommandCache = enumerator.Private("_relationalCommandCache");
        var selectExpression = relationalCommandCache.Private<SelectExpression>("_selectExpression");
        var factory = relationalCommandCache.Private<IQuerySqlGeneratorFactory>("_querySqlGeneratorFactory");
        var relationalQueryContext = enumerator.Private<RelationalQueryContext>("_relationalQueryContext");

        var sqlGenerator = factory.Create();
        var command = sqlGenerator.GetCommand(selectExpression);
        var parametersDict = relationalQueryContext.ParameterValues;

        return SubstituteVariables(command.CommandText, parametersDict);
    }

    private static string SubstituteVariables(string commandText, IReadOnlyDictionary<string, object> parametersDictionary)
    {
        var sql = commandText;
        foreach (var (key, value) in parametersDictionary)
        {
            var placeHolder = "@" + key;
            var actualValue = GetActualValue(value);
            sql = sql.Replace(placeHolder, actualValue);
        }

        return sql;
    }

    private static string GetActualValue(object value)
    {
        var type = value.GetType();

        if (type.IsNumeric())
            return value.ToString();

        if (type == typeof(DateTime) || type == typeof(DateTimeOffset))
        {
            switch (type.Name)
            {
                case nameof(DateTime):
                    return $"'{(DateTime)value:u}'";

                case nameof(DateTimeOffset):
                    return $"'{(DateTimeOffset)value:u}'";
            }
        }

        return $"'{value}'";
    }

    private static bool IsNullable(this Type type)
    {
        return
            type != null &&
            type.IsGenericType &&
            type.GetGenericTypeDefinition() == typeof(Nullable<>);
    }

    private static bool IsNumeric(this Type type)
    {
        if (IsNullable(type))
            type = Nullable.GetUnderlyingType(type);

        if (type == null || type.IsEnum)
            return false;

        return Type.GetTypeCode(type) switch
        {
            TypeCode.Byte => true,
            TypeCode.Decimal => true,
            TypeCode.Double => true,
            TypeCode.Int16 => true,
            TypeCode.Int32 => true,
            TypeCode.Int64 => true,
            TypeCode.SByte => true,
            TypeCode.Single => true,
            TypeCode.UInt16 => true,
            TypeCode.UInt32 => true,
            TypeCode.UInt64 => true,
            _ => false
        };
    }
}

这也许不能替代所有类型，但是大多数都涵盖了。随意扩展。

Answer 6

作为公共服务：

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);

然后是这些扩展方法（适用于.NET Core 1.0的IQueryableExtensions1，适用于.NET Core 2.0的IQueryableExtensions）：

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;
        }


    }


}

Answer 7

我根据@ nikolay-kostov答案得出的结论。

区别在于，我得到的SQL命令带有提取的参数，而不是硬编码的，这与EF Core将命令发送到数据库的方式更加一致。另外，如果要编辑命令并将命令发送到数据库，则最好使用参数。

private static class IQueryableUtils 
{
    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 = QueryCompilerTypeInfo.DeclaredFields.First(x => x.Name == "_queryModelGenerator");
    private static readonly FieldInfo queryContextFactoryField = QueryCompilerTypeInfo.DeclaredFields.First(x => x.Name == "_queryContextFactory");
    private static readonly FieldInfo loggerField = QueryCompilerTypeInfo.DeclaredFields.First(x => x.Name == "_logger");
    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 sql, IReadOnlyDictionary<string, object> parameters) ToSql<TEntity>(IQueryable<TEntity> query) where TEntity : class
    {
        var queryCompiler = (QueryCompiler)QueryCompilerField.GetValue(query.Provider);
        var queryContextFactory = (IQueryContextFactory)queryContextFactoryField.GetValue(queryCompiler);
        var logger = (Microsoft.EntityFrameworkCore.Diagnostics.IDiagnosticsLogger<DbLoggerCategory.Query>)loggerField.GetValue(queryCompiler);
        var queryContext = queryContextFactory.Create();
        var modelGenerator = (QueryModelGenerator)QueryModelGeneratorField.GetValue(queryCompiler);
        var newQueryExpression = modelGenerator.ExtractParameters(logger, query.Expression, queryContext);
        var queryModel = modelGenerator.ParseQuery(newQueryExpression);
        var database = (IDatabase)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 command = modelVisitor.Queries.First().CreateDefaultQuerySqlGenerator()
            .GenerateSql(queryContext.ParameterValues);

        return (command.CommandText, queryContext.ParameterValues);
    }
}

Answer 8

添加此答案的原因是，此处的所有建议在新的EF Core版本中均已失效（即，此处的所有答案在EF Core 2.2中均已失效）。以下代码在第一次尝试时对我有用，似乎与.NET Core版本无关（到目前为止）：https://blogs.msdn.microsoft.com/dbrowne/2017/09/22/simple-logging-for-ef-core/

Answer 9

对于EF Core 3和更高版本，EFCore.BulkExtensions具有ToParametrizedSql方法。我唯一的抱怨是它以Microsoft.Data.SqlClient的形式返回参数，因此有时我必须将它们转换为System.Data.SqlClient（如果这是我的连接类型）。

https://github.com/borisdj/EFCore.BulkExtensions

EFCore.BulkExtensions.IQueryableExtensions.ToParametrizedSql

Answer 10

对于 EF Core 3.1 solution above，在使用 System.InvalidCastException 之类的查询时，您可能会遇到 myQueryable.Where(x => ids.Contains(x.Id))（有关详细信息，请参见下文）。 （生成 SELECT ... FROM ... WHERE ID IN (...) 形式的 sql 语句）

System.InvalidCastException
  Message=Unable to cast object of type 'Microsoft.EntityFrameworkCore.Query.SqlExpressions.SqlParameterExpression' to type 'Microsoft.EntityFrameworkCore.Query.SqlExpressions.SqlConstantExpression'.
  Source=Microsoft.EntityFrameworkCore.Relational
  StackTrace:
   at Microsoft.EntityFrameworkCore.Query.QuerySqlGenerator.VisitIn(InExpression inExpression) in /_/src/EFCore.Relational/Query/QuerySqlGenerator.cs:line 577
   at Microsoft.EntityFrameworkCore.Query.SqlExpressionVisitor.VisitExtension(Expression extensionExpression) in /_/src/EFCore.Relational/Query/SqlExpressionVisitor.cs:line 37
   at System.Linq.Expressions.Expression.Accept(ExpressionVisitor visitor) in /_/src/System.Linq.Expressions/src/System/Linq/Expressions/Expression.cs:line 164
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node) in /_/src/System.Linq.Expressions/src/System/Linq/Expressions/ExpressionVisitor.cs:line 34

为了解决这个问题，将代码调整为类似的内容：

EF 核心 3.1

using System.Linq;
using System.Reflection;
using System.Collections.Generic;
using Microsoft.EntityFrameworkCore.Query.SqlExpressions;
using Microsoft.EntityFrameworkCore.Query;

public static string ToSql<TEntity>(this IQueryable<TEntity> query) where TEntity : class
{
    using var enumerator = query.Provider.Execute<IEnumerable<TEntity>>(query.Expression).GetEnumerator();
    var relationalCommandCache = enumerator.Private("_relationalCommandCache");
    var selectExpression = relationalCommandCache.Private<SelectExpression>("_selectExpression");
    var factory = relationalCommandCache.Private<IQuerySqlGeneratorFactory>("_querySqlGeneratorFactory");
    var relationalQueryContext = enumerator.Private<RelationalQueryContext>("_relationalQueryContext");
    var parameterValueBasedSelectExpressionOptimizer = relationalCommandCache.Private<ParameterValueBasedSelectExpressionOptimizer>("_parameterValueBasedSelectExpressionOptimizer");

    (selectExpression, _) = parameterValueBasedSelectExpressionOptimizer.Optimize(selectExpression, relationalQueryContext.ParameterValues);

    var sqlGenerator = factory.Create();
    var command = sqlGenerator.GetCommand(selectExpression);

    string sql = command.CommandText;
    return sql;
}

private static object Private(this object obj, string privateField) => obj?.GetType().GetField(privateField, BindingFlags.Instance | BindingFlags.NonPublic)?.GetValue(obj);
private static T Private<T>(this object obj, string privateField) => (T)obj?.GetType().GetField(privateField, BindingFlags.Instance | BindingFlags.NonPublic)?.GetValue(obj);

从EF Core查询中获取SQL代码

10 个答案:

实体框架核心3.x

EF 核心 3.1