public class ColumnCollection : CollectionBase

Public Class ColumnCollection
	Inherits CollectionBase

public ref class ColumnCollection : public CollectionBase

type ColumnCollection =  
    class
        inherit CollectionBase
    end

[C#]

//Instantiating a Workbook object
Workbook workbook = new Workbook();

//Obtaining the reference of the first worksheet
Worksheet worksheet = workbook.Worksheets[0];

//Add new Style to Workbook
Style style = workbook.CreateStyle();

//Setting the background color to Blue
style.ForegroundColor = Color.Blue;

//setting Background Pattern
style.Pattern = BackgroundType.Solid;

//New Style Flag
StyleFlag styleFlag = new StyleFlag();

//Set All Styles
styleFlag.All = true;

//Change the default width of first ten columns
for (int i = 0; i < 10; i++)
{
    worksheet.Cells.Columns[i].Width = 20;
}

//Get the Column with non default formatting
ColumnCollection columns = worksheet.Cells.Columns;

foreach (Column column in columns)
{
    //Apply Style to first ten Columns
    column.ApplyStyle(style, styleFlag);
}

//Saving the Excel file
workbook.Save("D:\\book1.xls");

[VB.NET]

'Instantiating a Workbook object
Dim workbook As New Workbook()

'Obtaining the reference of the first worksheet
Dim worksheet As Worksheet = workbook.Worksheets(0)

'Add new Style to Workbook
Dim style As Style = workbook.CreateStyles()

'Setting the background color to Blue
style.ForegroundColor = Color.Blue

'setting Background Pattern
style.Pattern = BackgroundType.Solid

'New Style Flag
Dim styleFlag As New StyleFlag()

'Set All Styles
styleFlag.All = True

'Change the default width of first ten columns
For i As Integer = 0 To 9
    worksheet.Cells.Columns(i).Width = 20
Next i

'Get the Column with non default formatting
Dim columns As ColumnCollection = worksheet.Cells.Columns

For Each column As Column In columns
    'Apply Style to first ten Columns
    column.ApplyStyle(style, styleFlag)
Next column

'Saving the Excel file
workbook.Save("D:\book1.xls")