Add the validation to the excel sheets

1. You need get the Range for which you want to add the validation.

//Select the specified cell
Range cell = worksheet.Cells[row, column];

2. Once you get the Range, you can call the Validation.Add method on the Range object.

//Delete any previous validation
cell.Validation.Delete();
//Add the validation, that only allowes selection of provided values.
cell.Validation.Add(<<pass the required parameters>>)

More information about the Validation methods and properties is available at
http://msdn.microsoft.com/en-us/library/microsoft.office.interop.excel.validation.add(office.11).aspx[^]