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If you don't understand or know something about the .NET Framework, the first place to look and learn is in the .NET Framework SDK[^]. There are several topics you should read, including Consuming Unmanaged DLL Functions[^], Marshaling Data with Platform Invoke[^], and about the DllImportAttribute[^] class.
A good site to check out for P/Invoke signatures (though not always written correctly for 32- and 64-bit platform support, since the use IntPtr for an unmanaged int commonly, which is actually processor-dependent) is pinvoke.net[^]. You won't find the functions for winmm.dll, however.
Below are a couple of examples:
[DllImport("winmm.dll", CharSet=CharSet.Auto)]
[return: MarshalAs(UnmanagedType.U4)]
private static extern int mciSendString(string command, string returnString,
[MarshalAs(UnmanagedType.SysUInt)]IntPtr returnSize, IntPtr callback);
[DllImport("winmm.dll")]
[return: MarshalAs(UnmanagedType.U4)]
private static extern int mixerMessage(IntPtr driverId,
[MarshalAs(UnmanagedType.SysUInt)]IntPtr msg,
[MarshalAs(UnmanagedType.SysUInt)]IntPtr param1,
[MarshalAs(UnmanagedType.SysUInt)]IntPtr param2);There are shortcuts and some attributes are not required, but these signatures will work on both 32- and 64-bit platforms so no assumptions are made.
Microsoft MVP, Visual C#
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Hi people,
I would like to gather your opinion on the following subject. I am working on a generic O/R mapping tool. Currently, it supports the following database-to-class situations:
1) 1 class per database table
2) 1 class per view which maps into one database table, or maps into several database tables, however, the fields which are required for update, still stay in one table.
I'm thinking of another approach: to have a few database tables for all types of objects in a business domain, something like this:
ClassesTable
Class Type
Entities.Order
Entities.Customer
ClassFieldsTable
FieldID - Class Type - FieldName
1 - Entities.Order - orderID
2 - Entities.Order - orderItem
3 - Entities.Customer - custID
4 - Entities.Customer - custName
FieldValuesTable
ID - FieldID - Value
1 - 1 - ord1
2 - 2 - Sock
3 - 3 - ALADDIN1
4 - 4 - Aladdin
5 - 1 - ord2
6 - 2 - handkerchief
etc.
The tables are related in the following way:
ClassTypes 1 ------ (ClassType) ------- * ClassFieldsTable
FieldValuesTable 1 ------(FieldID) ----- 1 ClassFieldTable
The O/RM layer dynamically constructs SQL commands to store and load business objects
to/from the database, and to perform different types of queries on objects in the
database with the help of object-oriented query builder.
The reasons behind this are:
1) Predefined database structure that will not change with the development of the
business application
2) Possible centralized storage for enterprise-level data to support long-running
business transactions and a common lock mechanizm
3) Still possible to create reports with 3d party tools by using views into the "basic" tables
Can you point me to any disadvantages in this approach?
Regards,
Serge (Logic Software, Easy Projects .NET site)
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1) Performance. For queries, because you always need multiple joins, and for inserts and updates, because you have a bottleneck in the FieldValues table.
2) Data types - you have not mentioned how you will solve the data type problem...you need either 1 table for each data type, or each data type needs to be represented in the FieldValues table, or something inbetween.
Its been done before - I know of one commercial product that uses this technique. I think the project manager did his thesis on it, and concluded that it was a viable way to go.
I'm not so sure.
my blog
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Hi, Steven!
Thanks for your reply.
Steven Campbell wrote:
1) Performance. For queries, because you always need multiple joins, and for inserts and updates, because you have a bottleneck in the FieldValues table.
Can you eloborate a bit on this?
2) Data types - you have not mentioned how you will solve the data type problem...you need either 1 table for each data type, or each data type needs to be represented in the FieldValues table, or something inbetween.
One thing that comes to my mind is to use SQL Server variant data type.
Regards,
Serge (Logic Software, Easy Projects .NET site)
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hai there,
i have few doubts on picture related queries & operations using C#
1. is it possible to read a picture format directly from a scanner using C# ?
2. is it possible to get the type of picture that if i read directly from a hard drive ?
3. i have a .doc or .xls file and i included few pictures using oledb techinics. I need to filter that perticular picture file or files from that .doc or .xls file using my c# code block. Is it possible ?
4. how can i compare picture files.if it is possible give me the technology behind this. Which technology will support this. is it possible with C# ?
Please feel free to contact.
Sreejith S S Nair - Bangalore
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sreejith ss nair wrote:
1. is it possible to read a picture format directly from a scanner using C# ?
Yes, with a TWAIN driver wrapped in managed code. I'm not sure of any third-party libraries that may exist (they probably do), but writing this requires a lot of knowledge of device drivers and TWAIN. You're best-off just having the scanner save the image and read it into managed code, or find a third-party library that does enscapsulate TWAIN drivers for your scanner. You may also be able to leverage WIA (Windows Image Acquisition).
sreejith ss nair wrote:
2. is it possible to get the type of picture that if i read directly from a hard drive ?
What? If you read it from a stream without knowing the ImageFormat? Use the Image.RawFormat property (inheritted by the Bitmap class).
sreejith ss nair wrote:
3. i have a .doc or .xls file and i included few pictures using oledb techinics. I need to filter that perticular picture file or files from that .doc or .xls file using my c# code block. Is it possible ?
Yes. You'll need to enumerate the objects in the compound document and determine what type they are. There are documented APIs in the Office automation documentation that can be installed with Office that detail this.
sreejith ss nair wrote:
4. how can i compare picture files.if it is possible give me the technology behind this. Which technology will support this. is it possible with C# ?
You need to perform a pixel-by-pixel comparison. Use LockBits on two Bitmaps and read through the BitmapData comparing the pixels of each image.
Take a look at a reply I wrote a day or two again in this forum about how to compare two MemoryStreams. The concept is the same, though the manner is a little different. You just loop through the pixels (may be multiple bytes) and compare them. Using unmanaged code is a little faster. See Christian Graus's articles on imaging in .NET for examples.
Microsoft MVP, Visual C#
My Articles
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Is it possible to give more idea in this doubt and your post.
3. i have a .doc or .xls file and i included few pictures using oledb techinics. I need to filter that perticular picture file or files from that .doc or .xls file using my c# code block. Is it possible ?
Yes. You'll need to enumerate the objects in the compound document and determine what type they are. There are documented APIs in the Office automation documentation that can be installed with Office that detail this.
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Is it possible to give more idea in this doubt and your post.
3. i have a .doc or .xls file and i included few pictures using oledb techinics. I need to filter that perticular picture file or files from that .doc or .xls file using my c# code block. Is it possible ?
Yes. You'll need to enumerate the objects in the compound document and determine what type they are. There are documented APIs in the Office automation documentation that can be installed with Office that detail this.
Please feel free to contact.
Sreejith S S Nair - Bangalore
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sreejith ss nair wrote:
Is it possible to give more idea in this doubt and your post.
Okay - this is really bugging me after so many posts. It's "question", not "doubt". Doubt is what you have when you don't believe something. A question is what you ask when you don't understand something.
I don't have any sample code to show you, nor do I have time to write any. Using the Office object model you can enumerate the objects in the document and there's plenty of documentation in the Office developer help files (don't bother checking MSDN - it has little to no documentation of the Office object model). You'll just have to read and discover for yourself like many of us regular responders here in this forum (and others) have done to learn.
Microsoft MVP, Visual C#
My Articles
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hai there,
Any idea about backward compatibility ?
how can i develop n-tier application using dotnet template
Please feel free to contact.
Sreejith S S Nair - Bangalore
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That makes no sense. What do you mean by "dotnet template"? There is no template. If you mean patterns, read about many different patterns in the MSDN Patterns and Practices[^] section, which contains information for n00bs to advanced developers.
If you want information on backward compatibility with assemblies (assembly versioning), then - as always - the information is all in the .NET Framework SDK. Read Configuring Applications[^], especially Specifying with Runtime Version to Use[^], Redirecting Assembly Versions[^], and Creating a Publisher Policy File[^].
Above, you must control your assembly versions. Do NOT use an asterisk in your AssemblyVersionAttribute, which is the default and can make you loose control very quickly.
You really must read about this stuff. IntelliSense won't help you and these concepts require a good understand that you can only gain from reading and (and experience with what you've read).
Microsoft MVP, Visual C#
My Articles
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hai there,
Please give me very good and indepth idea about debug and trace class. material link if fine.
Why are there five tracing levels in System.Diagnostics.TraceSwitcher?
Please feel free to contact.
Sreejith S S Nair - Bangalore
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sreejith ss nair wrote:
Why are there five tracing levels in System.Diagnostics.TraceSwitcher?
Read the documentation for the TraceSwitch and related content. It explains everything.
Microsoft MVP, Visual C#
My Articles
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hai there,
Please give me very good and indepth idea about debug and trace class. material link if fine.
Please feel free to contact.
Sreejith S S Nair - Bangalore
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fine & thanX
Please feel free to contact.
Sreejith S S Nair - Bangalore
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:-Ohai there,
i want to create an localized application which will run on any culture.
to do this where i want to start ? any materials ?
Please feel free to contact.
Sreejith S S Nair - Bangalore
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You nead to read up on Globalization and Localization (or Globalisation and Localisation - depending on which locale of English you are using  )
Also, just to publicise my own work a little, I wrote an article giving a basic introduction to localisation on .NET. You can find it here[^]. It is for the Compact Framework, but everything is applicable to the full framework also.
"You can have everything in life you want if you will just help enough other people get what they want." --Zig Ziglar
The Second EuroCPian Event will be in Brussels on the 4th of September
Can't manage to P/Invoke that Win32 API in .NET? Why not do interop the wiki way!
My Blog
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i didn't get your post.
Please feel free to contact.
Sreejith S S Nair - Bangalore
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What do you mean? What didn't you get?
"You can have everything in life you want if you will just help enough other people get what they want." --Zig Ziglar
The Second EuroCPian Event will be in Brussels on the 4th of September
Can't manage to P/Invoke that Win32 API in .NET? Why not do interop the wiki way!
My Blog
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your first paragraph. something about languages .....
Please feel free to contact.
Sreejith S S Nair - Bangalore
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hai Mr.Mackay,
Do u have any idea about my post which just below to this.
heading > "Lisence"
Please feel free to contact.
Sreejith S S Nair - Bangalore
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Sorry, but given the security requirements of a licence manager, I would seek to buy in a third party manager rather than attempt to make one myself.
"You can have everything in life you want if you will just help enough other people get what they want." --Zig Ziglar
The Second EuroCPian Event will be in Brussels on the 4th of September
Can't manage to P/Invoke that Win32 API in .NET? Why not do interop the wiki way!
My Blog
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sreejith ss nair wrote:
your first paragraph. something about languages
The topics you need to look up in any searches are "Localization" and "Globalization", in the brackets I made a comment refering to the fact that these spellings are American-English, however in other English-speaking locations the correct spelling is "Localisation" and "Globalisation" (note the "z" is replaced with an "s"). It was a lame attempt at a joke. Obviously it wasn't very funny.
I hope that clears up the misunderstanding.
"You can have everything in life you want if you will just help enough other people get what they want." --Zig Ziglar
The Second EuroCPian Event will be in Brussels on the 4th of September
Can't manage to P/Invoke that Win32 API in .NET? Why not do interop the wiki way!
My Blog
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hai Mr.Mackay,
Do u have any idea about my post which just below to this.
heading > "Lisence"
Please feel free to contact.
Sreejith S S Nair - Bangalore
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