How Can I Detect Redirected Console Input in C#?

Determining Redirected Console Input in C# Applications

Console applications rely heavily on input/output operations. However, the source of this input—whether a keyboard or a redirected stream (like a file)—can dramatically alter application behavior. This article demonstrates how to effectively detect redirected console input in C#.

Checking for Redirection

The most straightforward method uses the FileType() function. A helper class simplifies this check:

<code class="language-csharp">public static class ConsoleHelper {
    public static bool IsInputRedirected() {
        return FileType.Char != GetFileType(GetStdHandle(StdHandle.Stdin));
    }
}</code>

Implementation

To use the helper, simply call:

<code class="language-csharp">bool isRedirected = ConsoleHelper.IsInputRedirected();</code>

A true result indicates input originates from a source other than the keyboard (e.g., a file).

Underlying Native Methods

The helper utilizes these Win32 API functions:

• FileType: Enumerates file types (Unknown, Disk, Char, Pipe).
• StdHandle: Represents standard handles (Stdin, Stdout, Stderr).
• GetFileType: Retrieves the type of a given handle.
• GetStdHandle: Gets a handle to a standard device.

.NET 4.5 and Later Simplification

.NET Framework 4.5 and later versions provide a built-in, more concise method:

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

This directly returns a boolean indicating redirection status.

By employing these techniques, developers can build robust console applications that adapt their functionality based on the input source, enhancing user experience and application flexibility.

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