A sudoku solver written in C#. It is fairly performant, though there are definitely some improvements to be made. To run the code open the solution in VS2019 and ctrl + f5. Some sample sudokus in the required format can be found below. You can also exchange '0' for '.'.
000260701680070090190004500820100040004602900050003028009300074040050036703018000
032000005800300000904280001000400039000600050000010000020006708000004000095000060
000006000059000008200008000045000000003000000006003054000325006000000000000000000
000050001100000070060000080000004000009010300000596020080062007007000000305070200
000008100000000006010006450000289340049631005000745060000800013650093782000007094
400000805030000000000700000020000060000080400000010000000603070500200000104000000