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You need to be more specific about what you mean by "arbitrary data playback". A system restore involves a "pause, rewind and play" (but there's nothing to see).
It was only in wine that he laid down no limit for himself, but he did not allow himself to be confused by it.
― Confucian Analects: Rules of Confucius about his food
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To be more specific ...
My application is a signal system I have designed for "Ride On Railroads" (7.5" gauge typically here in the USA).
The system consists of controller nodes distributed around the railroad. Each of these nodes detects track occupancy, calculates which train should be permitted to proceed and sets signals accordingly.
All of this data (track occupancy, signal head settings, etc.) is broadcast on a single CAN Bus in real time.
There can be one or more PCs attached to the network for monitoring and control (NOT control of train movements, that's totally done by the controller nodes).
One of the things the PCs support is display of train movements to passengers as well as one or more dispatchers.
I want to record this CAN Bus data as a stream of 'change' events as well as periodic "key frame" records to a disk file. The key frame record records the current status of every object (track, signal, etc.) on the railroad. Thus, starting at a 'key frame' and proceeding forward in time you have a time record of everything that happened on the railroad.
I want to be able to switch the display screen from the 'live data stream' (what is currently happening on the railroad) and display what happened at an earlier time ... i.e.: replay the railroad activity.
So, I need to be able to support things like "play back the data stream from 5pm yesterday", etc.
This is done all the time with audio and video streams but I have not been able to find any examples of code that will do it for an arbitrary stream of data.
I also need to decide the file format that would be efficient for recording the data stream and allows somewhat random read start points. Least efficient, but would work, would be for me to just do a 'binary search' in the file by picking a point in the file and scanning for a key frame, check the time, and jump forward or backward depending on the result of the comparison. No complicated indexes needed. Writing of the stream to disk is a MUCH more frequent activity than read so writing needs to be optimized over reading/playback.
It's kind of like a data acquisition system that gathers a stream of data and you want to be able to play it back from an arbitrary point.
Again, I can roll my own but figured it was worth checking to see if something existed that was close to my needs but all my searches only show up tools for audio or video.
As an aside: forward seems easy, skip back "x seconds" is harder/less efficient.
For more information on the system in general see: http://www.minirailsolutions.com[^]
In this document is an example of the track display: SComm | MiniRailSolutions – Automatic Signals For Ride-on Railroads[^]
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I've never heard of any such tools, probably because of the infinite nature of "arbitrary data".
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"Play back" then simply depends on the "player" having a proper interface; i.e. the same one for real-time playing and historical.
In real-time, you add to a concurrent queue (enque / dequeue) AND a concurrent serial log (append). The real-time "playing" uses the "real-time" queue.
In play-back, you load what you want to the "play-back" queue (a reference) from the serial log, and a new instance of the player runs off of that.
It was only in wine that he laid down no limit for himself, but he did not allow himself to be confused by it.
― Confucian Analects: Rules of Confucius about his food
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What format is the data in? Can it be stored into a database in a sequential manner? If so the do as Bill suggested and divorce the real time (which should be recording the data into a database) process and the play back process.
If the data can be stored in a database then play back is a trivial matter.
Never underestimate the power of human stupidity -
RAH
I'm old. I know stuff - JSOP
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I would separate out the task of display of real-time "live" continuous state information from the task of doing a kind of animated slide-show starting from an initial state (key-frame). I think different strategies would be involved: streaming vs. moving back or forward in time in a data store.
«One day it will have to be officially admitted that what we have christened reality is an even greater illusion than the world of dreams.» Salvador Dali
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Thanks to all for the feedback. I am going to reexamine the amount of data involved and the expected frequency of recording .vs. playback to see if it warrants a database approach or another approach.
Thanks to all.
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Hi,
We have a C# windows forms application and I need to work with MS Word files to replace some text, table rows content, or add a new rows to an existed table, we need to know the best way.
I tried using Microsoft.Office.Interop.Word but this way may be old and must use the same office on the all pc's you install the application on it, if you use the MS Office 2007 then you must install it on any PC will use the application.
Please let me know the best way, tools to do that.
Thank You
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Basically, interop is pretty much your only real way - but using Word as a storage medium is the real problem!
There are various libraries that claim to do it - Google found this which lists a few: Reading doc and docx files using C# without having MS Office installed on server - Stack Overflow[^] - but I've not tested any.
Personally, I'd look for a better file format - there is no guarantee that what you read today will stay the same format tomorrow if MS decide to "add features".
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
"Common sense is so rare these days, it should be classified as a super power" - Random T-shirt
AntiTwitter: @DalekDave is now a follower!
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If you can use the newer Office formats, you can use the OpenXML SDK to work with the files without having Office installed.
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Interop is the only real method of updating Word. We had to make sure ALL users were on EXACTLY the same version of Word to use the application. It was updating legal documents that had to read exactly correctly and turned out to be one of the most painful operations I have ever had to do.
If you cannot control the version of Word on all clients then you have a serious problem.
Never underestimate the power of human stupidity -
RAH
I'm old. I know stuff - JSOP
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If you wanted to write a query that contains 'IF' clause, how would you do it?
Please revise this query:
mycommand.CommandText = "IF EXISTS(SELECT * FROM [MyData] WHERE NOT Wo = 'ABC' OR Code = 1200)";
If above statement satisfied:
INSERT INTO[MyData] VALUES('New001', 768353)";
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It's a 2 part act: One query to select; then an Insert based on the result of the first query.
You're using C# without stored procs; the "if" check is done on the client.
It was only in wine that he laid down no limit for himself, but he did not allow himself to be confused by it.
― Confucian Analects: Rules of Confucius about his food
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What do you mean by CLIENT? Do you mean that if statement must be in C# part? I have written a query in SQL Management Tool. I can use the IF statement and achieve what I want. But SQL CE gives errors in multiple sections. How can I write queries which have multiple lines in SQLCE and C#?
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I though it would be easier for you. You know ... partitioning the problem.
It was only in wine that he laid down no limit for himself, but he did not allow himself to be confused by it.
― Confucian Analects: Rules of Confucius about his food
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I know little about C# and how, once your SQL Query gets constructed as mycommand.CommandText, you'd use it from your C# frontend, but I'lll wager you're going to need some more TSQL describing the redirection that "IF EXISTS" intimates in order to complete a statement ... I assume there's a target of your INSERT, something like a TABLE (called [MyData]).
IF EXISTS
(
SELECT *
FROM [MyData]
WHERE NOT EXISTS [Wo] = 'ABC'
OR [Code] = 1200
)
INSERT INTO [MyData]
VALUES('New001', 768353)
END;
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Ok, How would you use it with
mycommand.CommandText = "write your sql statements";
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Can anyone please check this SQL CE query and revise its syntax for me?
insert into MyData values('test01', '1122/035', '666','ty01', 'tt01') where not exists (select * from MyData where 'test01', '1122/035', '666','ty01', 'tt01')
In query above, I add a new row to SQL data but it checks for duplicates before adding.
modified 5-Jun-21 2:45am.
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There is no such thing as a WHERE clause on an INSERT statement.
You have to write this as two queries. The first is the SELECT to see if anything is returned. If there isn't, then you can execute the INSERT query.
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Quote:
I found a solution on the internet which fixes it. You can use a command of the form:
INSERT INTO TableName (ColumnName)
SELECT '" + value + "' WHERE NOT EXISTS (
SELECT ColumnName from TableName WHERE Name = '" + value + "')";
Followed by an ExecuteNonQuery().
SQL Server Equivalent of MySQL INSERT IGNORE
It was only in wine that he laid down no limit for himself, but he did not allow himself to be confused by it.
― Confucian Analects: Rules of Confucius about his food
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My user needs to load some excel sheets and store some of their information into a SQL CE file. This SQL CE file contains a table with 5 columns. The rows will increase as the user adds their information into SQL. What is the best way to do this? Is there any SQL query that can check for duplicate values and if the new entry does not exist in the SQL file, adds it to the table?
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No, there is no query statement that will do that for you.
You could write up a stored procedure to do that in the database and call that stored procedure from your app with the appropriate data.
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I added my method below. Please read it.
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I never used SQL CE (compact edition)
Dave Kreskowiak wrote: You could write up a stored procedure to do that in the database and call that stored procedure from your app with the appropriate data.
, however, I always thought the stored procedures are not available there... Was I wrong? 
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