How Can I Efficiently Read Large Text Files in .NET?

Reading Large Text Files in .NET: Exploring Efficient Approaches

Working with large text files requires efficient techniques to handle the sheer volume of data. One common scenario is reading a 1 GB text file line by line. This guide explores optimal methods for this task.

StreamReader.ReadLine()

StreamReader is a common approach for reading text files. The ReadLine() method allows iterating through lines of the file. However, for large files, this method can be quite slow, as it reads the entire file into memory.

MemoryMappedFile

If available in .NET 4.0 or later, MemoryMappedFile is a recommended class specifically designed for handling large files. It mmaps the file into memory, allowing direct access to its contents without loading the entire file into memory.

Code Example

The following example code illustrates how to use MemoryMappedFile to read a large text file:

using System.IO.MemoryMappedFiles;
...

// Open the file
MemoryMappedFile mappedFile = MemoryMappedFile.CreateFromFile("largeFile.txt", FileMode.Open, null, 1024 * 1024 * 1024); // 1 GB buffer

// Create a view of the file
MemoryMappedViewAccessor accessor = mappedFile.CreateViewAccessor();

// Read the file
byte[] lineBytes = new byte[1024];
for (long i = 0; i <p><strong>Conclusion</strong></p><p>When dealing with large text files, MemoryMappedFile offers a more efficient solution compared to StreamReader.ReadLine(), allowing direct access to the data without loading the entire file into memory. For compatibility reasons, StreamReader.ReadLine() remains a viable option for earlier versions of .NET.</p>

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