this.gridDataBoundGrid1.BaseStylesMap["Column Header"].StyleInfo.Font.Bold = true;2) If the CellType of these summary cells is not "FormulaCell", then to get the Format to work, you need to set the style.CellValueType = typeof(double).
this.summaryGrid[1, i + 1].CellValue = (double) sum;Immediately after setting the format, if you try
string s = this.summaryGrid[1, i + 1].FormattedText;What is s?
this.summaryGrid[1, i + 1].FormattedText;should be what will be displayed in the grid cell, so I am not sure why 23.0 is not being shown in the cell. If you can post a sample project showing the problem, we can try to debug it here.