How Can I Determine if a C# Console Application's Input is from the Keyboard or a File?

Distinguishing Keyboard Input from File Redirection in C# Console Apps

This article demonstrates how to determine if a C# console application's input originates from the keyboard or a redirected file. This capability is vital for creating applications that adapt their behavior based on the input source.

Method Using P/Invoke

The Windows API function FileType() offers a solution. This functionality is wrapped in the following C# helper class:

<code class="language-csharp">public static class ConsoleEx
{
    private enum FileType { Unknown, Disk, Char, Pipe };
    private enum StdHandle { Stdin = -10, Stdout = -11, Stderr = -12 };

    [DllImport("kernel32.dll")]
    private static extern FileType GetFileType(IntPtr hdl);
    [DllImport("kernel32.dll")]
    private static extern IntPtr GetStdHandle(StdHandle std);

    public static bool IsInputRedirected
    {
        get { return FileType.Char != GetFileType(GetStdHandle(StdHandle.Stdin)); }
    }
}</code>

Implementation

To check for redirected input, simply use:

<code class="language-csharp">bool isRedirected = ConsoleEx.IsInputRedirected;</code>

Alternative: .NET 4.5 and Later

For .NET Framework 4.5 and later versions, the Console class provides built-in properties:

• Console.IsInputRedirected
• Console.IsOutputRedirected
• Console.IsErrorRedirected

These properties offer a more straightforward approach to detecting input redirection. Choose the method best suited to your project's .NET framework version.

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