CODEWITHSUNDEEP
vb.net
Wine Too
Wine Too

Reputation: 4655

Random access files at clean VB.NET way

After working some time in VB.NET I would like to get rid of Microsoft.VisualBasic dependencies.
Since with text files and string manipulation goes easy here I don't know what to do.

Is it possible to write equivalent code in VB.NET without using Microsoft.VisualBasic namespace and how this code should look like? 

Dim fnum As Integer = FreeFile()
FileOpen(fnum, "Setup\myadmin", OpenMode.Random, OpenAccess.ReadWrite, OpenShare.Shared, Len(idstruct))
FilePut(fnum, idstruct, 1) 'structure data to file in record 1
FileClose(fnum)

Upvotes: 2

Views: 2493

Answers (4)

Steven Doggart
Steven Doggart

Reputation: 43743

As much as I sympathise with your desire to remove all references to the Microsoft.VisualBasic namespace, and as much as I think that doing so has value, sometimes it's just not worth the trouble. The namespace does contain some useful tools which are not easily reproduced without it.

For instance, the TextFieldParser comes to mind. It allows you to easily read CSV and fixed-width files. There is no other class like it in the .NET framework. So, is it worth it to reinvent the wheel just so that you don't reference the Microsoft.VisualBasic namespace? I would argue that it's not worth it.

While it would be possible to reproduce the behavior of FileGet and FilePut using FileStream and the StreamReader, StreamWriter, BinaryReader, and BinaryWriter classes, it's probably not worth all the trouble. The FileGet and FilePut methods are provided specifically for backwards compatibility, so if compatibility with old systems is your goal, as much as it pains me to say it, using FileGet and FilePut is an appropriate solution.

However, some of this advice hinges on the type of data. If, for instance, the structure only contains fixed width strings, that would be very easy to duplicate with the StreamReader and StreamWriter, or with the TextFieldParser. Or, if it contains just integers, perhaps it will be easy to reproduce with the BinaryReader and BinaryWriter.

However, even if you can easily reproduce the logic using other non-VB-only classes, doing so doesn't gain you anything. In fact, your code will be more complicated and it will be less self-documenting. When you see code using FileGet and FilePut, not only is it easy to tell what is being done, but it is also obvious that it is for backwards compatibility. If you replace them with your own logic, the necessity for backwards compatibility would not be obvious without adding comments to the code.

If you don't like looking at them, which I can certainly understand, it may be worth wrapping them in a wrapper class. For instance, you could create a data-access style class with load/save methods which internally just use FileGet and FilePut. Doing so would be good practice anyway. That way, if you ever choose to store the data in a different format, or a different data source (such as a database), you could change it in the one class without having to rewrite all of your code.

Upvotes: 2

rory.ap
rory.ap

Reputation: 35270

One other thing I've just found is this MSDN page about My.Computer.FileSystem:

http://msdn.microsoft.com/en-us/library/0b485hf7%28v=vs.90%29.aspx

which I found was referred to from the MSDN page on FilePut:

http://msdn.microsoft.com/en-us/library/0s9sa1ab%28v=vs.90%29.aspx

From posts like this one It's my understanding that it's just a wrapper for System.IO anyway, but it supposedly provides a "more convenient and understandable" interface to the underlying IO functions.

Upvotes: 1

Ňɏssa Pøngjǣrdenlarp
Ňɏssa Pøngjǣrdenlarp

Reputation: 38875

Look at System.IO.FileStream. The approach is a bit different, but it is quite simple.

 Dim fs As New FileStream(mUserFile, FileMode.XXX, FileAccess.XXX)

or:

 Using fs as New FileStream....

 End Using

The main thing that will change is that rather than writing a structure, you would convert it to an array of bytes (Count would be the length of your array, offset 0 in your example):

 fs.Write(byt(), lOffset, lCount)

You COULD wrap it all up in a class to emulate the old random access file method if there it a lot of legacy code to support. There is also a BinaryReader and BinaryWriter and you could also look into serialization if the data is large but mostly static.

Upvotes: 0

rory.ap
rory.ap

Reputation: 35270

If you're referring to your use of the LEN() function (which is the only thing I can see that refers to Microsoft.VisualBasic namespace, unless I'm missing something), then you can just use String.Length instead. E.g. idstruct.Length, assuming idstruct is a String.

Upvotes: 0

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