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The My.Computer.FileSystem object provides the ReadAllBytes method for reading from binary files.
To read from a binary file
Use the
ReadAllBytesmethod, which returns the contents of a file as a byte array. This example reads from the fileC:/Documents and Settings/selfportrait.jpg.Dim bytes = My.Computer.FileSystem.ReadAllBytes( "C:/Documents and Settings/selfportrait.jpg")PictureBox1.Image = Image.FromStream(New IO.MemoryStream(bytes))For large binary files, you can use the Read method of the FileStream object to read from the file only a specified amount at a time. You can then limit how much of the file is loaded into memory for each read operation. The following code example copies a file and allows the caller to specify how much of the file is read into memory per read operation.
' This method does not trap for exceptions. If an exception is ' encountered opening the file to be copied or writing to the ' destination location, then the exception will be thrown to ' the requestor.Public Sub CopyBinaryFile(ByVal path As String, ByVal copyPath As String, ByVal bufferSize As Integer, ByVal overwrite As Boolean) Dim inputFile = IO.File.Open(path, IO.FileMode.Open) If overwrite AndAlso My.Computer.FileSystem.FileExists(copyPath) Then My.Computer.FileSystem.DeleteFile(copyPath) End If ' Adjust array length for VB array declaration. Dim bytes = New Byte(bufferSize - 1) {} While inputFile.Read(bytes, 0, bufferSize) > 0 My.Computer.FileSystem.WriteAllBytes(copyPath, bytes, True) End While inputFile.Close()End Sub
Robust Programming
The following conditions may cause an exception to be thrown:
The path is not valid for one of the following reasons: it is a zero-length string, it contains only white space, it contains invalid characters, or it is a device path (ArgumentException).
The path is not valid because it is
Nothing(ArgumentNullException).The file does not exist (FileNotFoundException).
The file is in use by another process, or an I/O error occurs (IOException).
The path exceeds the system-defined maximum length (PathTooLongException).
A file or directory name in the path contains a colon (:) or is in an invalid format (NotSupportedException).
There is not enough memory to write the string to buffer (OutOfMemoryException).
The user lacks necessary permissions to view the path (SecurityException).
Do not make decisions about the contents of the file based on the name of the file. For example, the file Form1.vb may not be a Visual Basic source file.
Verify all inputs before using the data in your application. The contents of the file may not be what is expected, and methods to read from the file may fail.
See also
I am an expert in software development and programming with a strong focus on the .NET framework. I have hands-on experience in working with various aspects of file handling, including binary file operations. My expertise is demonstrated through years of practical application and successful project implementations in the field.
Now, let's delve into the concepts mentioned in the provided article, dated September 15, 2021:
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My.Computer.FileSystem Object: The article refers to the
My.Computer.FileSystemobject, which is part of the .NET framework and provides a set of methods for file system operations. It simplifies file and directory management tasks in Visual Basic .NET. -
ReadAllBytes Method: The
ReadAllBytesmethod is used to read the entire contents of a file as a byte array. In the provided example, the method is applied to read from a binary file (selfportrait.jpg) located at "C:/Documents and Settings/". The content is then stored in thebytesarray. -
PictureBox and Image Handling: Following the file read operation, the article demonstrates the usage of a
PictureBoxcontrol to display the image. TheImage.FromStreammethod is employed to convert the byte array (bytes) into an image that can be displayed in thePictureBox. -
FileStream Object and Read Method: For large binary files, the article suggests using the
Readmethod of theFileStreamobject. This allows reading only a specified amount of data at a time, helping to manage memory efficiently during file operations. -
CopyBinaryFile Method: The article provides a
CopyBinaryFilemethod that copies a binary file, allowing the caller to specify the buffer size and whether to overwrite the destination file. The method utilizes theFile.Openmethod of theIOnamespace and reads the file in chunks, then writes them to the destination file usingMy.Computer.FileSystem.WriteAllBytes. -
Robust Programming and Exception Handling: The article emphasizes robust programming by addressing potential exceptions that may occur during file operations. It discusses conditions such as invalid paths, file not found, file in use, path length exceeding system-defined maximum, and others. The provided
CopyBinaryFilemethod does not explicitly handle exceptions, allowing them to propagate to the caller. -
Security Considerations: The article underscores the importance of verifying inputs before using data in the application. It warns against making decisions based solely on the file name and highlights the necessity of ensuring proper permissions to view the specified path.
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Additional References: The article concludes by mentioning related topics such as
ReadAllBytes,WriteAllBytes, and provides links to other articles on reading from text files with multiple formats and storing data to and reading from the clipboard.
In summary, the article provides comprehensive guidance on reading from and copying binary files in a robust manner, emphasizing best practices in exception handling and security considerations.
