✅ Help in 2d matrix

var lines = Enumerable.Repeat(1, 4).ToArray();
var columns = Enumerable.Repeat(lines, 4).ToList();
columns[0][0] = 2;
Console.WriteLine(System.Text.Json.JsonSerializer.Serialize(columns));

//[[2,1,1,1],[2,1,1,1],[2,1,1,1],[2,1,1,1]]

var lines = Enumerable.Repeat(1, 4).ToArray();
var columns = Enumerable.Repeat(lines, 4).ToList();
columns[0][0] = 2;
Console.WriteLine(System.Text.Json.JsonSerializer.Serialize(columns));

//[[2,1,1,1],[2,1,1,1],[2,1,1,1],[2,1,1,1]]