EntityFramework进阶（三）- 根据IQueryable获取DbContext

本系列原创博客代码已在EntityFramework6.0.0测试通过，转载请标明出处

有时候我们要通过IQueryable获取所在的DbContext信息，这是完全可以的。

以下代码从个人开源框架中抽取而出

using System;
using System.Data.Entity;
using System.Data.Entity.Core.Objects;
using System.Data.Entity.Infrastructure;
using System.Data.Entity.Infrastructure.Interception;
using System.Linq;
using System.Reflection;

/*
* CopyRight ©2017 All Rights Reserved
* 作者:Rex Sheng
*/
namespace SuperNet.EntityFramework.Extensions
{
    public static class IQueryableExtensions
    {
        public static DbContext GetDbContext<TEntity>(this IQueryable<TEntity> query) where TEntity : class
        {
            ObjectQuery<TEntity> objectQuery = null;
            DbQuery<TEntity> dbQuery = null;
            if(query is ObjectQuery<TEntity>)
            {
                objectQuery = (ObjectQuery<TEntity>)query;
            }
            else
            {
                if(query is DbQuery<TEntity>)
                {
                    dbQuery = (DbQuery<TEntity>)query;
                    var propers = dbQuery.GetType().GetProperty("InternalQuery", BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
                    if (propers == null)
                    {
                        throw new Exception("未能从IQueryable表达式找到DbContext。您确定此表达式来自Ef DbContext吗?");
                    }
                    var obj = propers.GetValue(dbQuery, null);
                    propers = obj.GetType().GetProperty("ObjectQuery", BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
                    if (propers == null)
                    {
                        throw new Exception("未能从IQueryable表达式找到DbContext。您确定此表达式来自Ef DbContext吗?");
                    }
                    objectQuery = propers.GetValue(obj, null) as ObjectQuery<TEntity>;
                    if (objectQuery == null)
                    {
                        throw new Exception("未能从IQueryable表达式找到DbContext。您确定此表达式来自Ef DbContext吗?");
                    }
                }
                else
                {
                    throw new Exception("未能从IQueryable表达式找到DbContext。您确定此表达式来自Ef DbContext吗?");
                }
            }
            return objectQuery.Context.GetDbContext();
        }

    }
}