Handling Input Streams in .NET Applications for Command Pipelines

#csharp #cli

When building .NET applications intended for use in console environments, it's essential to design your program to be flexible. One common requirement is to detect whether input is being provided via a command pipeline (i.e., from stdin) and, if not, to perform a default action. This article explores how you can inspect the input stream in your .NET application and adjust behavior accordingly.

Command Pipelines in Linux

In Linux, the pipe operator (|) connects the output of one command to the input of another. For example:

echo "Hello, World!" | dotnet run

In this command, the output of echo is sent to your .NET application via standard input. Your application must determine whether such piped input is present in order to correctly process data or use fallback logic.

Checking for Input in a .NET Application

There are several methods to detect if there's data available on the input stream. Below, we discuss three common approaches.

Detecting Input Redirection

A good workaround is to determine whether the standard input is redirected. .NET provides the Console.IsInputRedirected property, which returns:

true when the input is coming from a pipe or a file.
false when the input is from an interactive terminal session.

Example: Conditional Input Handling

Below is an example that demonstrates how to check for input redirection before attempting to read data. This approach avoids the blocking behavior when no piped data is provided:

if (Console.IsInputRedirected)
{
    string input = Console.In.ReadToEnd();
    Console.WriteLine("Received Input: " + input);
}
else
{
    Console.WriteLine("No input detected; proceeding with default action.");
}

Integrating with Command Pipelines

By combining these methods with Linux command pipelines, your .NET application can operate intelligently based on the source of its input. For instance, consider the pipeline:

cat sample.txt | dotnet run

When data is piped into your application from sample.txt, one of the methods above detects the input and processes it. If no data is piped, your application can execute alternative logic. This flexibility makes your application robust and adaptable to various runtime conditions.