linq列表<a> select many <a,b>

Question

Let's say I have:

List<string> sqlServerNames;

and a method:

List<string> GetDatabases( string serverName );

And I want a single query to get a list of { serverName, databaseName }

Is there a way to do this with Linq?

sqlServerNames.????

So for example, if I have two servers, ".", and "SQL2016".

And "." has "db1", "db2"
And "SQL2016" has "db3"

I'd want:

".", "db1"
".", "db2"
"SQL2016", "db3"

Probably with an anonymous type.

Answer 1

尝试看起来像这样的东西：

var dictionary = {
    coolSound: {
        sound: function (mode) {
            return new Howl({src: ["sounds/" + mode + "/bubbles.mp3"]});
        }
    }
}

Answer 2

建议使用SelectMany的另一个重载。其他答案需要为每个服务器名称分配一个新的枚举/枚举/委托，而这并不是。

sqlServerNames.SelectMany(serverName => GetDatabases(serverName),
                          (serverName, databaseName) => new
                          {
                              ServerName = serverName,
                              DatabaseName = databaseName
                          });

相当于：

from serverName in sqlServerNames
from databaseName in GetDatabases(serverName)
select new
{
    ServerName = serverName,
    DatabaseName = databaseName
};

Answer 3

您可以使用SelectMany方法：

sqlServerNames
    .SelectMany(sn => GetDatabases(sn)
                        .Select(dbn => new { 
                                            ServerName = sn,
                                            DatabaseName = dbn 
                                            }
                                )
                );