什么相当于Linq中的“SELECT SYSTEM_USER”

Question

I can get the identity of the currently logged in SQL Server user by using the SYSTEM_USER value, but is there a way to do this via linq somehow? I'm looking for something like the below:

var query = from u in dataContext.Users
            where u.domainname == dataContext.system_user
            select u.fullname;

Using something like Environment.UserName won't work in the event a non-domain user authenticates via VPN, and querying via a separate statement is undesirable because I'd like to use just one statement to get the data.

Answer 1

Calling system functions can be done by creating new functions in the database which can be mapped further in the ORMs. It depends then on the ORM capabilities regarding to mapping user database functions.

CREATE FUNCTION dbo.fnSystemUser () returns varchar(120)
AS
BEGIN
    return (select SYSTEM_USER)
END

LINQ2SQL and EF will create a single SQL statement for the following LINQ query.

var query = from u in dataContext.Users
            where u.domainname == dataContext.fnSystemUser()
            select u.fullname;

Answer 2

LINQ itself knows nothing about your database so no. If you're talking about LINQ 2 Entities (as some keywords in your code sample imply) you may be able to use one of the ExecuteQuery overloads (or one of its relatives) with your explicit SQL statement.

As an alternative, you could parse the connection string to get the user's log on details. I believe the SqlConnectionStringBuilder class should be able to tell you the user name and password of the user used to connect to the database if you aren't using Windows auth.

Answer 3

Try this:

    class System
    {
        public string SystemUser { get; set; }
    }

   var query = dataContext.ExecuteQuery<System>("select SYSTEM_USER AS 'SystemUser'");