Скачать или смотреть How to Detect End of Stream in BinaryReader.ReadBytes(int) in C#

Learn how to handle the lack of `EndOfStreamException` in `BinaryReader.ReadBytes(int)` method in C# by detecting stream end effectively.
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Understanding BinaryReader and Stream Reading in C#

When working with streams in C# , especially when using the BinaryReader class, you might encounter some peculiar behavior when trying to read bytes from a stream. Specifically, the ReadBytes(int) method does not throw an EndOfStreamException if it reaches the end of the stream. This can lead to confusion or unintended behavior in your applications if you are not aware of how to properly manage this scenario.

The Problem at Hand

As a developer using BinaryReader, you may expect that reading operations will throw an exception when they can no longer read from a stream, particularly when you've defined how many bytes you wish to retrieve. In most other methods, the EndOfStreamException would alert you when the end is reached. However, the ReadBytes(int) method simply returns a smaller byte array if it encounters an end-of-stream condition, leaving you without any explicit sign of this condition.

For example, if you ask to read 10 bytes from a stream, but only 5 bytes are available because the end has been reached, you’ll receive an array of length 5 instead of an exception being thrown.

A Simple Solution: Checking the Length of the Array

Fortunately, there is a straightforward way to detect whether you have hit the end of a stream when using the ReadBytes(int) method. Here’s how you can implement this solution:

Step 1: Reading the Bytes

You will use the ReadBytes(int) method to attempt to read your desired number of bytes from the stream.

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Step 2: Checking the Resulting Length

Next, compare the length of the bytes array you received to the number of bytes you attempted to read. If these two values do not match, it signifies that the end of the stream was reached before your request could be fully satisfied. You can then throw an EndOfStreamException or take another appropriate action.

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Example Code

Here’s a complete example to illustrate this concept:

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In this example, if the example.dat file does not contain enough data, the code will throw an exception, allowing you to handle the situation gracefully in your application.

Conclusion

Understanding the behavior of BinaryReader.ReadBytes(int) when it comes to end-of-stream detection is crucial for writing robust and error-free code in C# . By implementing a simple length check, you can effectively manage scenarios where the stream runs dry, ensuring your application behaves as expected. Always remember that checking the result of your read operations can prevent subtle bugs and improve the overall reliability of your code.