FeedCenter/Application/MainWindow/CommandLine.cs

using System;

namespace FeedCenter;

public partial class MainWindow
{
    private void HandleCommandLine(string commandLine)
    {
        // If the command line is blank then ignore it
        if (commandLine.Length == 0)
            return;

        // Pad the command line with a trailing space just to be lazy in parsing
        commandLine += " ";

        // Look for the feed URL in the command line
        var startPosition = commandLine.IndexOf("feed://", StringComparison.Ordinal);

        // If nothing was found then exit
        if (startPosition <= 0) return;

        // Advance past the protocol
        startPosition += 7;

        // Starting at the URL position look for the next space
        var endPosition = commandLine.IndexOf(" ", startPosition, StringComparison.Ordinal);

        // Extract the feed URL
        var feedUrl = commandLine[startPosition..endPosition];

        // Add the HTTP protocol by default
        feedUrl = "http://" + feedUrl;

        // Create a new feed using the URL
        HandleNewFeed(feedUrl);
    }
}