我正在使用 Entity Framework Core,我需要查看正在生成哪些 SQL 代码。在 Entity Framework 的早期版本中,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 ToTraceString 在 EF Core 中不可用。
如何在 EF Core 中执行类似的操作?
最佳答案
EF 核心 5/6/网络 5/6
query.ToQueryString()
参见Documentation ToQueryString()和 What's New in EF Core 5.0
var query = _context.Widgets.Where(w => w.IsReal && w.Id == 42);
var sql = query.ToQueryString();
对于较旧的网络核心框架,可以使用扩展。
核心2.1.2
using System.Linq;
using System.Reflection;
using Microsoft.EntityFrameworkCore.Query;
using Microsoft.EntityFrameworkCore.Query.Internal;
using Microsoft.EntityFrameworkCore.Query.Expressions;
using Microsoft.EntityFrameworkCore.Query.Sql;
using static Microsoft.EntityFrameworkCore.DbLoggerCategory;
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;
}
}
EF Core 3.0
public static string ToSql<TEntity>(this IQueryable<TEntity> query)
{
using var enumerator = query.Provider.Execute<IEnumerable<TEntity>>(query.Expression).GetEnumerator();
var enumeratorType = enumerator.GetType();
var selectFieldInfo = enumeratorType.GetField("_selectExpression", BindingFlags.NonPublic | BindingFlags.Instance) ?? throw new InvalidOperationException($"cannot find field _selectExpression on type {enumeratorType.Name}");
var sqlGeneratorFieldInfo = enumeratorType.GetField("_querySqlGeneratorFactory", BindingFlags.NonPublic | BindingFlags.Instance) ?? throw new InvalidOperationException($"cannot find field _querySqlGeneratorFactory on type {enumeratorType.Name}");
var selectExpression = selectFieldInfo.GetValue(enumerator) as SelectExpression ?? throw new InvalidOperationException($"could not get SelectExpression");
var factory = sqlGeneratorFieldInfo.GetValue(enumerator) as IQuerySqlGeneratorFactory ?? throw new InvalidOperationException($"could not get IQuerySqlGeneratorFactory");
var sqlGenerator = factory.Create();
var command = sqlGenerator.GetCommand(selectExpression);
var sql = command.CommandText;
return sql;
}
请参阅 RosiOli 的要点
EF Core 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 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);
此问题也由 EF net core team 跟踪并计划在下一个版本中发布。
关于c# - 从 Entity Framework Core IQueryable<T> 获取 SQL 代码,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/37527783/