How do you read binary data from a file in C#?

Question

Anubhav Kumar · Answer

To read binary data from a file in C#, you typically use one of the following:
1. File.ReadAllBytes()
Reads the entire file into a byte array.
byte[] data = File.ReadAllBytes(@"C:\path	o\file.bin");
Simple and useful when the entire file can fit in memory.Returns a byte[].
2. FileStream (for reading in chunks or large files)
Gives more control for reading part of the file or working with large files.
using (FileStream fs = new FileStream(@"C:\path	o\file.bin", FileMode.Open, FileAccess.Read))
{
    byte[] buffer = new byte[fs.Length];
    int bytesRead = fs.Read(buffer, 0, buffer.Length);
}
You can also read in smaller chunks if fs.Length is too large.
3. BinaryReader (for structured binary data)
Useful if you're reading primitives like integers, floats, strings, etc., from a binary format.
using (FileStream fs = new FileStream(@"C:\path	o\file.bin", FileMode.Open, FileAccess.Read))
using (BinaryReader reader = new BinaryReader(fs))
{
    int value = reader.ReadInt32();     // Reads a 4-byte int
    double d = reader.ReadDouble();     // Reads an 8-byte double
    byte[] bytes = reader.ReadBytes(10); // Reads 10 bytes
}
Summary
Method
Use Case
File.ReadAllBytes
Simple, small to medium files
FileStream
Large files, fine-grained control
BinaryReader
Structured binary formats (e.g., headers, fixed fields)
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How do you read binary data from a file in C#?

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1 Answers

1. `File.ReadAllBytes()`

2. `FileStream` (for reading in chunks or large files)

3. `BinaryReader` (for structured binary data)

Summary

Liked By

Method	Use Case
`File.ReadAllBytes`	Simple, small to medium files
`FileStream`	Large files, fine-grained control
`BinaryReader`	Structured binary formats (e.g., headers, fixed fields)