I did some work on my Vista laptop yesterday where everything was working fine and then copied the Service library (that contains the service i wanted to host) to my main dev box (Win7), added it to my Windows Service host and hacked some quick code/config to have it created by the service and running.

The service started fine and the logs were saying that the service host for the WCF service i just added was all good, but from my clients I kept getting:

System.ServiceModel.EndpointNotFoundException: Could not connect to net.tcp://localhost:8733/...Service. The connection attempt lasted for a time span of 00:00:02.0323046. TCP error code 10061: No connection could be made because the target machine actively refused it 127.0.0.1:8733

Hmm, must be some Win7 security goo. So i spent the next *hour* trying a gazzilion of things - security? turned it off and no go, firewall? some weird policy? configured it and created a console app that opened the port and it was working fine. Need to do netsh http iplisten? that's for http, but who knows.... nothing still. Ok, let's try another binding instead, still same issue... . Ok, let's trace the client and server setting up WCF diagnostic traces... nothing relevant on the server and i already know what the client is going through. Ok, run under the debugger and see if there's anything weird... still nothing. Just looks like the wcf service is "muted" but it does not complain when i start it, and I know i'm creating the host and starting one by one.... I cannot be the only one having this problem so let's see what live.com finds... many different issues but i've already covered most of the tips or they don't apply.
At this point I'm starting to lower the level of investigation to figure what's going on with the ports, so i just try to use telnet

>telnet localhost 8733
Connecting To localhost...Could not open connection to the host, on port 8733: Connect failed

ok, let me use netstat to confirm that i've used the right port and protocol (which is probably what i should have done to begin with):

> netstat -a -o | findstr 8733
>

nothing! i'm absolutelly sure that i'm only using netTcpBinding and i review my code and config and yes, that's the port!
I use netstat again to verify what other ports might be opened for my process (pid 5868 - not to confuse with port nb)

> netstat -a -o | findstr 5868
>

nothing again!
At this point i'm really confused, but the only logical explanation is that my hosting code is busted, so i review it again and compare it to the last version... and finally understand what happened.

I added some tracing to know in detail when each ServiceHost was created and in doing so, i removed a "kind of important" line by accident

Msg 207, Level 16, State 1, Procedure usp_Main_GetCPUHistory, Line 6
Invalid column name 'cpu_ticks_in_ms'.

Here's a peek at the code (from setup.sql that ships with the Performance Dashboard):

create procedure MS_PerfDashboard.usp_Main_GetCPUHistory

as

begin

      declare @ts_now bigint

      select @ts_now = cpu_ticks / convert(float, cpu_ticks_in_ms) from sys.dm_os_sys_info
...

Hmm, what is going on !? Ah, this is Sql 2k8!

At this point i was about to switch to using the new super cool Activity Monitor in SQL2k8, but i was still intrigued, why wasn't this working?
I'm so used to Performance Dashboard that I wanted to know whether this was not going to work against Sql 2k8.

After some live searching i found that the column had been removed (well, i already knew that :)) and that it was due to some imprecision with its value.
The next question was how to fix the query in Sql 2k8, and it turned out to be a very trivial fix. 
Looking at sys.dm_os_sys_info 2k8 schema and at the original query using cpu_ticks_in_ms i saw a very interesting column (ms_ticks):

Column name	Data type	Description
cpu_ticks	bigint	Current CPU tick count. CPU ticks are obtained from the processor's RDTSC counter. It is a monotonically increasing number.
ms_ticks	bigint	Number of milliseconds since the computer was started.

The reason that column was interesting is because cpu_ticks / convert(float, cpu_ticks_in_ms) looks awefuly similar (ticks/(ticks/ms) == ms) to what ms_ticks already provides!
I ran some tests to make sure this column was good in both sql 2k5 and 2k8:

select cpu_ticks / ms_ticks as ratio_ticks_in_ms, cpu_ticks, ms_ticks from sys.dm_os_sys_info

The first column (ratio_ticks_in_ms) remained (mostly - within 0.000001% variance which i believe is due to rounding errors in ms_ticks) constant (and surprise, it was roughly my CPU frequency in ms - number of CPU ticks per millisecond). Note this happened in both SQL 2k5 and 2k8 (and i verified this across 3 different boxes). In SQL 2k5 i also added cpu_ticks_in_ms to the output and again it was within 0.000001%.

So, it seemed weird that in SQL 2k5 the query was written to divide cpu_ticks / cpu_ticks_in_ms given that ms_ticks is also present in sys.dm_os_sys_info 2k5. I can't think of any good reason (other than minimizing the rounding error of ms_ticks) and since ms_ticks was not dropped in 2k8 it was probably as reliable in 2k5 so i'll assume that was just some copy/paste, historical reasons...

On any case, i then changed the original stmt to

create procedure MS_PerfDashboard.usp_Main_GetCPUHistory

as

begin

      declare @ts_now bigint

      select @ts_now = ms_ticks from sys.dm_os_sys_info

and ran setup.sql again.

I haven't tested all the reports, but all i've tested (main, costliest queries and some others) all seem to be working fine!

So, there you go. If you are running into errors trying to deploy SQL Server Performance Dashboard into 2k8 just change setup.sql as shown above and you should be good.

That said i should say that Activity Monitor + Performance Data Collector and reports in Sql 2k8 are SIMPLY AWESOME and you should definetely look at them too.

PS: It has been a long time since i've published anything and very commonly I wish I had posted something that I (or somebody else) end up needing again. So, i'm trying to keep up to date again.

and

Improving .NET Application Performance and Scalability
https://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnpag/html/scalenet.asp

My favorite quote:
"If your software does not meet its performance objectives, your application is unlikely to be a success.
If you do not know your performance objectives, it is unlikely that you will meet them"

I should note that i ONLY pass and get arrays as strings on very specific cases (usually perf, test or dbg related).
Whenever possible i use relational operations only, especially for returning collections. Sometimes it is useful though to be able to return a single column with more than one elm, especially when the actual destination of the data is a function that expects a delimiter separated list.

That said, getting a bunch of params as a string array can be done like this:

DECLARE @outStringArray VARCHAR(MAX)
SET @outStringArray = NULL

SELECT    @outStringArray = ( COALESCE( NULLIF( @outStringArray + ',', '' ), '' ) + Name )
FROM      sys.objects

SELECT    @outStringArray

The interesting part is COALESCE( NULLIF( @outStringArray + ',', '' ), '' ) + Name which should read:
if @outStringArray is not NULL, then return the current string + ',' + Name. If it is null, return '' + Name.

We return '' + Name, because if we return NULL + Name, then NULL + something is NULL and our string would never grow.
You could also use SELECT CASE WHEN syntax, but i prefer this more compact form of saying the same. (after some time using this on queries you learn the meaning quite fast)
You could also use SQLCLR, xml (though not exactly a comma separated thing) and recursive functions.

Again, you can have specialized versions to deal with NULLs in the string (doing + COALESCE( Name, 'N/A') instead of + Name for example), to deal with different types, as well as different sort orders, more than one string field (e.g: + Name + ':' + Value).

Another use for this is sometimes when you want to compare hierarquical data the queries can become complex, and this way you can kind of serialize the hierarquies and then do a simple string comparison... (more on this on future posts)

1. Adding parameters to T-SQL with default values 
2. Passing a string with some delimiter and building a table from that

1. Adding parameters to T-SQL with default values is something like:

CREATE PROC GetCustomersById
(
   @CustomerId1     INT = NULL
   , @CustomerId2   INT = NULL
   ...
) AS
BEGIN
   SELECT Customer.CustomerId
          , Customer.Name
          , ...
   FROM   Customer
   WHERE  Customer.CustomerId IN ( @CustomerId1, @CustomerId2 )
END

There are some variations to the way one can consume the values, like storing them on a temp table or table variable, using COALESCE,... .

For simple stuff this works well but it does not scale as you add more parameters, or you need to pass in collections of related parameters (like structures). It starts to get messier.

2. Passing a string with some delimiter and building a table from that

For this method, we need a way to convert a string into a table. For that i use a function that returns a table variable. That's very convenient because one can use it directly on the queries as well as store it on local table variables.

/*
    Used to convert a delimited string into a table
    Ex: SELECT * FROM StringArray2Table( 'one,two,three,four,five', ',' )

    Notes: not dealing with overflow of elements, and when empty elms are found they
           are converted to NULL.
*/
CREATE FUNCTION StringArray2Table
(
    @stringArray VARCHAR(MAX)       -- delimited string array (max elm size = 255)
    , @delimiter CHAR(1) = ','      -- , by default
)
RETURNS @Table  TABLE
                    (
                        ix int identity(1,1)  -- useful to correlate two arrays and
                                              -- preserve order of elements
                        , elm VARCHAR(255)    -- elmts may overflow, not being checked
                    )
AS
BEGIN

    DECLARE @elm VARCHAR(255)
    DECLARE @from INT
    DECLARE @ix INT

    SET @from = 1 -- start from the beginning

    SET @ix = CHARINDEX( @delimiter, @stringArray, @ix )

    WHILE (@ix > 0) -- while there's a match
    BEGIN
        SET @elm = SUBSTRING( @stringArray, @from, @ix - @from )

        IF ( @ix = @from )
            INSERT INTO @Table( elm ) VALUES ( NULL )
        ELSE
            INSERT INTO @Table( elm ) VALUES ( @elm )

        SET @from = @ix + 1
        SET @ix = CHARINDEX( @delimiter, @stringArray, @from )  -- find next
    END

    IF ( @from - 1 <= len( @stringArray ) )    -- last elm
    BEGIN
        SET @elm = SUBSTRING( @stringArray, @from, 255 )

        IF LEN(@elm) > 0
            INSERT INTO @Table( elm ) VALUES ( @elm )
        ELSE
            INSERT INTO @Table( elm ) VALUES ( NULL )
    END

    RETURN
END

and then one can use it like

CREATE PROC GetCustomersById
(
   @CustomerList    VARCHAR(MAX)
) AS
BEGIN
   SELECT Customer.CustomerId
          , Customer.Name
          , ...
   FROM   Customer
          INNER JOIN dbo.StringArray2Table( @CustomerList, ',' ) CustArray
              ON Customer.CustomerId = CustArray.elm
END

I use some variations of this function, specialized by return type (return int for example), not returning the index, returning empty strings instead of NULL, returning more than one column (useful especially for "dictionary" like structures, e.g. 'Caption:asdasd,Height:2312,Width:123').

When i use this function i always have control over the input data and make sure it does not conflict with the delimiter. Of course, it's easy to come up with a convention to avoid delimiter usage inside the elements (like SQL does for 's for example).

There are other ways to pass in arrays, though i don't use them as often mainly because they are a bit more involved and imply more dependencies/configuration. The other options are xml type/OPENXML, varbinary, using SQLCLR (SQL2K5), etc...

I'll blog randomnly mainly on System.Data, Xml and SQL Server, as they are closely related to my current job (perf for System.Xml, System.Data (DataSet especially) and MSXML)

All feedback (questions, flames, comments...) is welcome.