How to Fix FileNotFoundException in C# – Beginner Guide with Examples

Encountering a FileNotFoundException in C# can be confusing, especially if you’re new to programming. This exception occurs when your program tries to access a file that doesn’t exist at the specified path.

Don’t worry—this is a common issue, and it’s usually easy to resolve once you understand what’s going on.

In this guide, we’ll walk through why this error happens, how to fix it, and how to prevent it in the future.

Table of Contents

What Causes This Error?

A FileNotFoundException typically occurs when:

1. The File Path Is Incorrect

Your code points to a file that doesn’t exist or has a typo in the path.

File.ReadAllText("data.txt"); // But the file is missing or misnamed

2. The File Was Moved or Deleted

If a file was manually moved or deleted after your application was written, the path may no longer be valid.

3. The File Is in the Wrong Directory

If you’re using relative paths, your program may look for the file in the wrong folder—especially when run from a different location or environment.

4. Permissions or Access Issues

The file exists, but the application doesn’t have access to it (though this more often throws a UnauthorizedAccessException).

How to Fix It

Fix 1: Double-Check the File Path

Make sure the file name and path are correct.

File.ReadAllText(@"C:\Users\YourName\Documents\data.txt");

Why it works: Ensuring the exact path prevents the program from looking in the wrong place.

Fix 2: Use `File.Exists()` Before Accessing

Always verify the file exists before reading or writing.

if (File.Exists("data.txt"))
{
    string content = File.ReadAllText("data.txt");
}
else
{
    Console.WriteLine("File not found.");
}

Why it works: It adds a safety check, so your app doesn’t crash if the file is missing.

Fix 3: Use Try/Catch Block

Gracefully handle the error if the file might not be present.

try
{
    string content = File.ReadAllText("data.txt");
}
catch (FileNotFoundException ex)
{
    Console.WriteLine("Could not find the file: " + ex.Message);
}

Why it works: Try/catch allows your app to continue running even if the file isn’t there.

Real Example

Problematic Code

string content = File.ReadAllText("report.csv");
Console.WriteLine(content);

Error: System.IO.FileNotFoundException: Could not find file 'report.csv'

Corrected Version

if (File.Exists("report.csv"))
{
    string content = File.ReadAllText("report.csv");
    Console.WriteLine(content);
}
else
{
    Console.WriteLine("File not found. Please check the path.");
}

Tips to Prevent This Error

Always validate file paths before use
Use full absolute paths in production code when possible
Wrap file access in try/catch blocks
Log missing files during development for quick debugging

Conclusion

The FileNotFoundException can be frustrating, but it’s easily manageable with careful coding habits. Use path validation, exception handling, and clear logging to make your applications more robust.

Bookmark this page as a handy reference the next time this error pops up.