[]
Gets or sets the zero-based index of the column displayed as the outline column.
The outline column displays hierarchical rows as a tree structure based on the indent levels in the worksheet.
int ColumnIndex { get; set; }
Property ColumnIndex As Integer
worksheet.Range["A1:A3"].Value = new object[,] {{"Name"}, {"Node 1"}, {"Node 1.1"}};
worksheet.Range["A3"].IndentLevel = 1;
IOutlineColumn outlineColumn = worksheet.OutlineColumn;
outlineColumn.ColumnIndex = 0;
int columnIndex = outlineColumn.ColumnIndex;