/// <summary>
/// 创建EF上下文对象，已存在就直接取，不存在就创建，保证线程内是唯一
/// </summary>
/// <returns></returns>
public static DbContext Create()
{
DbContext dbContext = CallContext.GetData("DbContext") as DbContext;
if (dbContext == null)
{
dbContext = new TutorEntities();
CallContext.SetData("DbContext", dbContext);
}
return(dbContext);
}
