Cell Style Alignment on a range

Based on this comment from the OP, "I found the problem. apparentlyworksheet.Cells[y + 1, x + 1].HorizontalAlignment", I believe the real explanation is that all the cells start off sharing the same Style object. So if you change that style object, it changes all the cells that use it. But if you just change the cell's alignment property directly, only that cell is affected.

This works good

worksheet.get_Range("A1","A14").Cells.HorizontalAlignment = 
                 Microsoft.Office.Interop.Excel.XlHAlign.xlHAlignLeft;

Maybe declaring a range might workout better for you.

// fill in the starting and ending range programmatically this is just an example. 
string startRange = "A1";
string endRange = "A1";
Excel.Range currentRange = (Excel.Range)excelWorksheet.get_Range(startRange , endRange );
currentRange.Style.HorizontalAlignment = Microsoft.Office.Interop.Excel.XlHAlign.xlHAlignLeft;