How to calculate the record length of an array of structure

Question

0.00/5 (No votes)

See more:

I have the following structure:

VB

Public Structure Aliment
              Public Alino As Integer
              <VBFixedString(83)> Public NomUS As String
              <VBFixedString(50)> Public NomFR As String
              <VBFixedString(24)> Public Categ As String
              Public Paramali() As Double
        End Structure

Then I have an array of this structure

Public TousALI() As Aliment

The array Paramali() is redimensioned:

ReDim Preserve TousALI.Paramali(80)

The data stored in the TousALI array, comes from a .txt file.
I load it, display it in a datagridview and it works perfectly.

But now I want to store the data in a random access file:

FileOpen(1, FileAliRand, OpenMode.Random, OpenAccess.Write, , 813)

But the next line :
FilePut(1, TousALI(I)) gives me an error: Incorrect record length.

the record lenght, 813 is the total number of bytes.

How to calculate the actual number of bytes of my array ?

Thanks for help

What I have tried:

I have tried many different length, but it doesn't work

Posted 28-Apr-17 16:57pm

Michel PERRIN

Updated 28-Apr-17 18:23pm

PIEBALDconsult

v2

Add a Solution

Comments

NightWizzard 29-Apr-17 3:39am

Well, I don't know how you came to a total length of 813? If you calculate the byte count in memory, an Integer will take 2 bytes and each double 8 bytes. In your example above this will give a total of 829 bytes in memory: 640 for 80 doubles, 2 for the int and for each string it's length plus 10 bytes overhead. If you're writing a binary file, the record length should be 829. If you're writig a text file, the numeric parameters have to be converted to string - in this case the string length for each numerical value can differ. For example: setting the Integer to 1000 still needs 2 bytes in memory for the Integer but the string will have a length of 4 plus the 10 bytes overhead = 14!!
In VB.NET you also can try to use either the length property:
size = Aliment.Length
or this method:
Marshal.SizeOf(Aliment)
Hope this will help you to solve the problem - good luck!

Richard MacCutchan 29-Apr-17 3:56am

Integers take 4 bytes, or 8 in 64-bit mode.

NightWizzard 29-Apr-17 4:24am

Thanks Richard - you're right. I confused this with old VB6/VBA - maybe I'm doing this job too much years. For Michel here the link to the .NET datatype summarize:
https://msdn.microsoft.com/en-us/library/s3f49ktz.aspx

Maciej Los 30-Apr-17 5:20am

If you're using VB.NET, you should use BinaryFormater instead of FileOpen method, etc.

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)