private void Btn_OpenGrid_Click(object sender, EventArgs e) { var op = new OpenFileDialog(); op.Filter = "avlsdk files (*.avlsdk)|*.avlsdk"; op.ShowDialog(); if (File.Exists(op.FileName)) { new SudokuForm(SudokuFileReader.ReadGridCode(File.ReadAllText(op.FileName)), op.FileName).Show(); } }