Hi Johnie,
Thank you for using Syncfusion products.
XlsIO supports to format the texts and merging the cells. You can achieve the cell merging from the following code snippet.
//Creating a range
IRange range = sheet.Range["C10"];
range.Text = "Sample of merging cells";
range.CellStyle.Color = Color.Blue;
range.CellStyle.Font.Color = ExcelKnownColors.Yellow;
range.CellStyle.Font.Bold = true;
//Merging the cells
sheet.UsedRange["C10:E10"].Merge(false);
Also, we have provided a sample that illustrates the text formatting and cells merging in the following link.
Merging_Cells.zip
Please let us know if the provided solution resolved you issue or you need any clarification.
Regards,
Johnson
Merging_Cells_41069c9b.zip