sb-marshalling-repro.cs

sb-marshalling-repro.cs

using System;
using System.Runtime.InteropServices;
using System.Text;

namespace ConsoleApp162
{
    class Program
    {
        [DllImport("user32.dll", CharSet = CharSet.Unicode)]
        static extern uint CharLowerBuffW([In, Out] StringBuilder lpsz, uint cchLength);

        static void Main()
        {
            var sb = new StringBuilder().AppendLine("HELLO").AppendLine("WORLD").AppendLine("FROM MONO");
            CharLowerBuffW(sb, (uint)sb.Length);
            Console.WriteLine(sb);
        }
    }
}