[英]Silverlight Entity Framework Dynamic Connection String
I have the same data model on a bunch of different servers. 我在一堆不同的服务器上有相同的数据模型。 I want to dynamically create a connection string based on who my user is and what they are doing.
我想根据用户是谁以及他们在做什么动态创建连接字符串。
My users can have multiple databases on multiple servers. 我的用户可以在多个服务器上拥有多个数据库。 I need a clean way to build a connectoin string when I create my DomainService.
创建DomainService时,我需要一种干净的方法来构建连接字符串。
I see that the DomainService has an override (inherited from LinqToEntitiesDomainService) called CreateObjectContext() that would allow me to set any connection string I want, then return the new entity and life is good. 我看到DomainService有一个重写(继承自LinqToEntitiesDomainService),称为CreateObjectContext(),它将允许我设置所需的任何连接字符串,然后返回新实体,并且生活很美好。 The problem is, the CreateObjectContext() gets called after the constructor, so I can't set a string via an invoke method.
问题是,CreateObjectContext()在构造函数之后被调用,所以我无法通过invoke方法设置字符串。 Also, I've tried to create a new parameterized constructor on the DomainService, but it never gets copied to the DomainContext on the client.
另外,我尝试在DomainService上创建一个新的参数化构造函数,但从未将其复制到客户端上的DomainContext中。
The CreateObjectContext() would work great if I was able to pull my connection string, but since I have to use data from the client to figure out which DB to connect, this obviously won't work. 如果我能够拉出我的连接字符串,CreateObjectContext()会很好用,但是由于我必须使用来自客户端的数据来确定要连接的数据库,所以这显然行不通。
The more I think about it, the more I feel a custom constructor is exactly what I need - just can't figure out how to get that done. 我考虑的越多,我就越觉得自定义构造函数正是我所需要的-只是不知道如何完成该工作。
What am I missing? 我想念什么?
I found a solution. 我找到了解决方案。 For those that are interested, here it is:
对于那些感兴趣的人,这里是:
This feels a bit like a hack, but it's the only solution I could come up with. 感觉有点像黑客,但这是我能想到的唯一解决方案。 Thanks to Sally Xu over at forums.silverlight.net for the ideas.
感谢Sally Xu在forums.silverlight.net上获得的想法。
Since each of my users can have mulitiple databases on multiple servers, I needed to find a way to create the ConnectionString before the DomainService was used the first time. 由于我的每个用户都可以在多个服务器上拥有多个数据库,因此我需要在首次使用DomainService之前找到一种创建ConnectionString的方法。 Each time the user selects a new project from the UI, I set a cookie like this:
每次用户从UI中选择一个新项目时,我都会设置如下cookie:
private void SetCookie(string cookieName, string cookieValue)
{
DateTime expireDate = DateTime.Now + TimeSpan.FromDays(1);
string newCookie = cookieName + "=" + cookieValue + ";expires=" + expireDate.ToString("R");
HtmlPage.Document.SetProperty("cookie", newCookie);
}
The cookieName is SelectedProjectId
and the cookieValue is the current selected project in my UI. cookieName是
SelectedProjectId
,而cookieValue是UI中当前选择的项目。
Then I create a new DomainService as normal, but I override CreateObjectContext()
. 然后,像往常一样创建一个新的DomainService,但是我覆盖了
CreateObjectContext()
。 This method gets called the very first time you reference your DomainService object. 首次引用DomainService对象时,将调用此方法。 My override looks like this:
我的覆盖看起来像这样:
protected override ProjectEntities CreateObjectContext()
{
long projectId = -1;
StringBuilder connection;
if (System.Web.HttpContext.Current.Request.Cookies["SelectedProjectId"] != null)
{
projectId = Convert.ToInt64(System.Web.HttpContext.Current.Request.Cookies["SelectedProjectId"].Value);
}
else throw new Exception("Selected Project ID Exception"); // temporary
// Verify this user has access to the DB just in case it's spoofed
// Lookup project ID in my database to get the database name and server name
// Load template connection string found in web.config
// Replace the template holders for SERVER_NAME and DATABASE_NAME with above lookup values
return new ProjectEntities(MyDynamicConnectionString);
}
Again, this is a bit hackish, but it was the only way I could find to dynamically create a connection string for my needs. 再说一次,这有点骇人听闻,但这是我可以找到动态创建满足我需求的连接字符串的唯一方法。 I hope this helps someone else...
我希望这可以帮助其他人...
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