Added function to read persisted sudoku

SudokuSolver/RawSudokuGrid.cs

@@ -0,0 +1,76 @@
+using System;
+using System.Data;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+
+namespace SudokuSolver;
+
+class SerializedOuterObject
+{
+
+    [JsonPropertyName("newboard")]
+    public SerializedNewBoard NewBoard { get; set; }
+
+    public SerializedOuterObject()
+    {
+        this.NewBoard = new SerializedNewBoard();
+    }
+}
+
+class SerializedNewBoard
+{
+    [JsonPropertyName("grids")]
+    public List<SerializedGrid> Grid { get; set; }
+
+    public SerializedNewBoard()
+    {
+        this.Grid = new List<SerializedGrid>();
+    }
+}
+
+
+class SerializedGrid
+{
+
+    [JsonPropertyName("value")]
+    public List<List<int>> Value { get; set; }
+
+    public SerializedGrid()
+    {
+        this.Value = new List<List<int>>();
+    }
+}
+
+public class RawSudokuGrid
+{
+    private readonly List<List<int>> grid;
+
+    public List<List<int>> Grid { get { return grid; } }
+
+    public RawSudokuGrid(List<List<int>> grid)
+    {
+        this.grid = grid;
+    }
+
+    public override string ToString()
+    {
+        string ret = "";
+        foreach (List<int> row in grid)
+        {
+            foreach (var item in row)
+            {
+                ret += $"{item} ";
+            }
+            ret += "\n";
+        }
+        return ret;
+    }
+
+    public static RawSudokuGrid LoadFile(string filename)
+    {
+        using FileStream stream = File.OpenRead(filename);
+        SerializedOuterObject ser = JsonSerializer.Deserialize<SerializedOuterObject>(stream)!;
+        return new RawSudokuGrid(ser.NewBoard.Grid[0].Value);
+    }
+}