FileNotFoundException

A FileNotFoundException is raised when dealing with file IO. This exception is raised when you access a file that must exist for the method to proceed.

C# type info

This exception normally is encountered in programs that include the System.IO namespace. It can be caused by a StreamReader constructor, or many other classes.

Example

StreamReader will throw a FileNotFoundException when you try to read a file that does not exist. The following program shows the FileNotFoundException being raised.

using System;
using System.IO;

class Program
{
    static void Main()
    {
        try
        {
            // Read in nonexistent file.
            using (StreamReader reader = new StreamReader("not-there.txt"))
            {
                reader.ReadToEnd();
            }
        }
        catch (FileNotFoundException ex)
        {
            // Write error.
            Console.WriteLine(ex);
        }
    }
}
System.IO.FileNotFoundException: Could not find file '...'

Catching FileNotFoundException

The runtime will locate the catch statement specified in the program, and the body of the catch block will be executed.

Discussion

Here we discuss some ways you can fix this exception. An error message could be printed. If you do not know if the file exists, it is often better use the File.Exists method.

Summary

This program causes the FileNotFoundException to be thrown, by trying to use StreamReader on a nonexistent file. We noted the C# language's exception handling construct in this case.