Here is another way to cover entire column.
// Cover entire column A
CellArea ca = CellArea.CreateCellArea("A", "A");
This will work with both XLS and XLSX format.
Please see the following sample code, execute it at your end and also read its comments. You will get two output Excel files. One in XLS format and other in XLSX format.
Now enter 200 (or any value greater than 100) in these cells and you will get validation error.
C#
// Create workbook
Workbook workbook = new Workbook();
// Accessing the Validations collection of the worksheet
ValidationCollection validations = workbook.Worksheets[0].Validations;
// Cover entire column A
CellArea ca = CellArea.CreateCellArea("A", "A");
// Creating a Validation object
Validation validation = validations[validations.Add(ca)];
// Setting the validation type to whole number
validation.Type = ValidationType.WholeNumber;
// Setting the operator for validation to Between
validation.Operator = OperatorType.Between;
// Setting the minimum value for the validation
validation.Formula1 = "10";
// Setting the maximum value for the validation
validation.Formula2 = "100";
// Save in XLS format
workbook.Save("output.xls", SaveFormat.Excel97To2003);
// Remove the area of validation and add it again
validation.RemoveArea(ca);
validation.AddArea(ca);
// Save in XLSX format
workbook.Save("output.xlsx");
Note: I am working as Developer Advocate at Aspose