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Home Forums Explain the difference between StreamReader and File.ReadAllLines(). – MindStick
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1 Answers

Anubhav Sharma
Anubhav Sharma 19 May 2025
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The difference between StreamReader and File.ReadAllLines() in C# lies mainly in how they read the file and when you would use each.

File.ReadAllLines(string path)

  1. Reads all lines of a text file at once.
  2. Returns a string[] (array of strings).
  3. File is opened, read, and closed automatically.
  4. Not suitable for very large files (can use a lot of memory).

Example:

string[] lines = File.ReadAllLines("example.txt");
foreach (string line in lines)
{
    Console.WriteLine(line);
}

StreamReader

  1. Reads a file line-by-line or character-by-character.
  2. Gives more control over reading (e.g., read a specific number of lines, skip lines, read partial content).
  3. Better for large files or streamed reading.
  4. You manually control the reading process and resource disposal (usually with using).

Example:

using (StreamReader reader = new StreamReader("example.txt"))
{
    string line;
    while ((line = reader.ReadLine()) != null)
    {
        Console.WriteLine(line);
    }
}

Summary of Differences

Feature File.ReadAllLines() StreamReader
Reads entire file Yes No (line-by-line or custom reading)
Returns string[] Each line via ReadLine()
Memory usage High (if file is large) Low (reads as needed)
Suitable for large files No Yes
Custom read logic No Yes
Ease of use Simple Requires more control

When to Use Which?

  1. Use File.ReadAllLines() for small to medium files when you want all lines immediately.
  2. Use StreamReader for large files or when you need streamed/customized reading logic.
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