实体框架“意外连接状态”例外 [英] Entity Framework "Unexpected Connection State" Exception

问题描述

经过三个小时的调试和搜索，我希望有人在这里有一个答案。实体框架（使用MySQL）如果我连续快速调用以下函数（例如，相距0.1秒），则会引发以下异常。

System.InvalidOperationException：意外的连接状态。当使用包装提供程序时，请确保在包装的DbConnection上实现StateChange事件。

但是，有时该功能无任何问题。第一个 ToList（）调用中抛出异常：

  void InsertOrUpdateMaterials（List< Material> materials）
 {
 var id = GetUserId（）; 
 var materialIds = materials.Select（x => x.MaterialId）.ToList（）; 
 
 //从DB中删除旧材料
 var oldMaterials = Db.Materials.Where（p => p.CreatedBy == id&& 
 materialIds.Contains p.MaterialId））ToList（）; // exception 
 Db.Materials.RemoveRange（oldMaterials）; 
 Db.SaveChanges（）; 
 
 //将以前的材料替换为列表
中的新材料Db.Materials.AddRange（materials）; 
 Db.SaveChanges（）; 
} 
  

奇怪的是，这个错误从未发生在开发服务器上，所以我研究了可能配置问题无效。

有时，实体框架会抛出：

系统.Data.Entity.Core.EntityCommandExecutionException：已经有一个与此Connection关联的开放DataReader必须先关闭。

再次指向到 ToList（）调用。任何想法？

解决方案

对于可能有类似问题的其他人。基于上述注释，代码使用缓存的数据库上下文。创建数据库上下文之后，应用程序中安装了db-connection（无 StateChange 处理程序）。连接崩溃后，应用程序使用缓存的数据库上下文来执行一些操作。

创建一个新的数据库上下文解决了这个问题。 $ b

After three hours of debugging and searching, I'm hoping someone here has an answer. Entity Framework (using MySQL) throws the following exception if I call the following function quickly in succession (e.g. < 0.1 seconds apart).

System.InvalidOperationException: Unexpected connection state. When using a wrapping provider ensure that the StateChange event is implemented on the wrapped DbConnection.

However, sometimes the function works without any problems. The exception is thrown on the first ToList() call:

void InsertOrUpdateMaterials(List<Material> materials)
{
    var id = GetUserId();
    var materialIds = materials.Select(x => x.MaterialId).ToList();

    // Remove old materials from DB
    var oldMaterials = Db.Materials.Where(p => p.CreatedBy == id && 
            materialIds.Contains(p.MaterialId)).ToList(); // exception
    Db.Materials.RemoveRange(oldMaterials);
    Db.SaveChanges();

    // Replace previous materials with the new ones in list
    Db.Materials.AddRange(materials);
    Db.SaveChanges();
}

Oddly, this error never occurred on the development server, so I looked into possible configuration issues to no avail.

Sometimes, Entity Framework throws:

System.Data.Entity.Core.EntityCommandExecutionException: There is already an open DataReader associated with this Connection which must be closed first.

Again pointing to the ToList() call. Any ideas?

解决方案

For other people that might a similar problem. Based on the above comments it seems that the code uses a cached db-context. After the db-context was created the db-connection broke (no StateChangehandler was installed in the application). After the connection breakdown the application used the cached db-context to perform some operations on it.

Creating a new db-context solved the problem.

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