C# scripting (dotnet script), snippets & REPL

Concept & use-cases

From snippet to app

using System;

// In a script, you can write Console.WriteLine("Hi") at top-level.
// Here we show the equivalent in a normal app (C# 6 friendly).
public class Program
{
  public static void Main(string[] args)
  {
    Console.WriteLine("Hello from a small snippet!");
    // In scripting, this could be a one-liner without class/namespace.
  }
}

Tiny utility idea

using System;
using System.IO;

// A small utility that counts lines containing a keyword.
// As a script, this could be a few lines; here it is a full app.
public class Program
{
  static int CountMatches(string path, string keyword)
  {
    if (!File.Exists(path)) return 0;
    int count = 0;
    string[] lines = File.ReadAllLines(path);
    for (int i = 0; i < lines.Length; i++)
    {
      if (lines[i].IndexOf(keyword, StringComparison.OrdinalIgnoreCase) >= 0) count++;
    }
    return count;
  }

  public static void Main(string[] args)
  {
    // Demo: create a tiny file, then count matches.
    string p = "data.csv";
    File.WriteAllLines(p, new string[] { "apple,10", "banana,5", "Apple,7" });
    Console.WriteLine("Rows with apple: " + CountMatches(p, "apple"));
  }
}

Snippet style helpers

using System;

// Keep helpers small; call them quickly from Main (as you would in a script).
public class Program
{
  static int Add(int a, int b) { return a + b; }
  static string Upper(string s) { return s == null ? "" : s.ToUpperInvariant(); }

  public static void Main(string[] args)
  {
    Console.WriteLine("Add: " + Add(2, 3));
    Console.WriteLine("Upper: " + Upper("hello"));
  }
}

Safety & hygiene

Good use-cases

Why scripting

Recap