Set cell value using Excel interop

Question

Ok, so I'm trying to set the value of a cell with the excel interop library. I am able to do it with the following:

sheet.Cells[row, col] = value;

but it's terribly slow for how many I'm setting. So I'm trying to go this route:

Range excelRange = sheet.UsedRange;
excelRange.Cells.set_Item(row, col, value);

The code executes, but no data is put in the cell. Any suggestions on what I'm missing? Thanks!

Answer 1

Your first method should work fine for any reasonable (and a lot of unreasonable) amounts of cells, provided you have disabled screen updating (Application.ScreenUpdating = false). The Knowledgebase Article describing how to set cells using C# accesses by row and column as well.

Answer 2

Have you tried setting all of the values at once, rather than iterating through your array and setting one cell at a time? That way you only have to pass data over the COM boundary once, rather than once per cell.

Excel is very flexible in this regard. Try the following:

int[] intArray = new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
Range rng = excelApp.get_Range("A1", "J1");
rng.Value = intArray; 

You should this faster than iterating over each of the cells you're wanting to set.

Other than that, turn off ScreenUpdated as Andy suggests and also consider setting calculation to manual until you've finished your copy process.