Fix the cell width in Word using Open XML SDK - openxml

Question

I have a table with one row in a docx file and I want to add some rows. For the first existing row I set the GridSpan to 3. In the next one I want add a row only with two cell, then I have the result as on the picture. How can I fix the new row width to the table width? The same I want to do, when I add only a one cell in the new row.
My code:
private static TableRow AddRow(WordprocessingDocument docx, Table tbl, int cellsQuantity)
{
TableRow newRow = new TableRow();
var firstCell = tbl.Descendants<TableRow>().First()
.Descendants<TableCell>().First();
firstCell.Append(new TableCellProperties(new GridSpan() { Val = 3 }));
for (int i = 0, max = cellsQuantity; i < max; i++)
{
// TableCellProperties tcp = new TableCellProperties(new TableCellWidth() { Width = firstCell.TableCellProperties.TableCellWidth.Width, Type = firstCell.TableCellProperties.TableCellWidth.Type });
TableCell cell = new TableCell(new Paragraph(new Run(new Text("test"))));
newRow.AppendChild(cell);
}
tbl.Append(newRow);
return newRow;
}

Answer 1

Ok, I thing I got it :)
private static TableRow AddRow(WordprocessingDocument docx, Table tbl, int cellsQuantity)
{
TableRow newRow = new TableRow();
var grid = tbl.Descendants<TableGrid>().First();
var firstCell = tbl.Descendants<TableRow>().First()
.Descendants<TableCell>().First();
firstCell.Append(new TableCellProperties(new GridSpan() { Val = 4 }));
int ind = 0;
int[] widthPerColumn = new int[] { 3070, 1536, 1535, 3071 };
grid.Descendants<GridColumn>().ToList().ForEach(x =>
{
x.Width = widthPerColumn[ind++].ToString();
});
int[] gridSpan = null;
switch (cellsQuantity)
{
case 4:
gridSpan = new int[] { 1, 1, 1, 1 };
break;
case 3:
gridSpan = new int[] { 1, 2, 1 };
break;
case 2:
gridSpan = new int[] { 2, 2 };
break;
case 1:
gridSpan = new int[] { 4 };
break;
default:
throw new InvalidOperationException("The cellsQuantity variable must have a value from [1,4] range");
}
for (int i = 0, max = cellsQuantity; i < max; i++)
{
TableCellProperties tcp = new TableCellProperties(new GridSpan() { Val = gridSpan[i] });
TableCell cell = new TableCell(tcp, new Paragraph(new Run(new Text("test"))));
newRow.AppendChild(cell);
}
tbl.Append(newRow);
return newRow;
}

Answer 2

TableCell tCell = new TableCell();
tCell.Append(new TableCellProperties(
new GridSpan { Val = table.LastChild.ChildElements.Count },
new Justification { Val = JustificationValues.Right })
);