The sample demonstrates how to provide a dropdownlist for valid data

                     
using System;

using Spire.Xls;

namespace DropDownList
{
    class Program
    {
        private static void CreateSampleData(Worksheet sheet)
        {
            sheet.Range["D8"].Text = "Country";
            //set the datasource of the E8
            sheet.Range["X1"].Text = "Lucy";
            sheet.Range["X2"].Text = "Bolivia";
            sheet.Range["X3"].Text = "Brazil";
            sheet.Range["X4"].Text = "Canada";
            sheet.Range["X5"].Text = "Chile";
            sheet.Range["X6"].Text = "Colombia";
            sheet.Range["X7"].Text = "Cuba";
            sheet.Range["X8"].Text = "Ecuador";
            sheet.Range["X9"].Text = " Salvado";
            sheet.Range["X10"].Text = "Guyana";
            sheet.Range["X11"].Text = "Jamaicatates";
            sheet.Range["X12"].Text = "Mexico";
            sheet.Range["X13"].Text = "Nicaragua";
            sheet.Range["X14"].Text = "Paraguay";
            sheet.Range["X15"].Text = "Peru";
            sheet.Range["X16"].Text = "United";
            sheet.Range["X17"].Text = "Uruguay";
            sheet.Range["X18"].Text = "Venezuel";

            CellRange rangeName = sheet.Range["E8"];
            rangeName.DataValidation.AllowType = CellDataType.Formula;
            rangeName.DataValidation.DataRange = sheet.Range["X1:X18"];
            rangeName.DataValidation.IgnoreBlank = true;
            rangeName.Activate();
            //hide column X                                 
            sheet.HideColumn(sheet.Range["X1"].Column);

            sheet.Range["D10"].Text = "Capital";
            //set the datasource of the E9
            sheet.Range["Y1"].Text = "Buenos Aires";
            sheet.Range["Y2"].Text = "La Paz";
            sheet.Range["Y3"].Text = "Brasilia";
            sheet.Range["Y4"].Text = "Ottawa";
            sheet.Range["Y5"].Text = "Santiago";
            sheet.Range["Y6"].Text = "Bagota";
            sheet.Range["Y7"].Text = "Havana";
            sheet.Range["Y8"].Text = "Quito";
            sheet.Range["Y9"].Text = "San Salvador";
            sheet.Range["Y10"].Text = "Georgetown";
            sheet.Range["Y11"].Text = "Kingston";
            sheet.Range["Y12"].Text = "Mexico City";
            sheet.Range["Y13"].Text = "Managua";
            sheet.Range["Y14"].Text = "Asuncion";
            sheet.Range["Y15"].Text = "Lima";
            sheet.Range["Y16"].Text = "Washington";
            sheet.Range["Y17"].Text = "Montevideo";
            sheet.Range["Y18"].Text = "Caracas";
            //Binding the datasource                 
            CellRange rangeCapital = sheet.Range["E10"];
            rangeCapital.DataValidation.AllowType = CellDataType.Formula;
            rangeCapital.DataValidation.DataRange = sheet.Range["Y1:Y18"];
            rangeCapital.DataValidation.IsSuppressDropDownArrow = false;
            rangeCapital.Activate();
            //hide coulumn Y
            sheet.HideColumn(sheet.Range["Y1"].Column);

            sheet.Range["D12"].Text = "Continent";
            //set the datasource of the F9
            CellRange rangeContinent = sheet.Range["E12"];
            rangeContinent.DataValidation.AllowType = CellDataType.Formula;
            rangeContinent.DataValidation.Values = new String[] { "South America", "North America" };
            rangeContinent.DataValidation.IsSuppressDropDownArrow = false;
            rangeContinent.Activate();

            //Set the column's width
            sheet.Range["E8"].Text = "Please select the country";
            sheet.Range["E10"].Text = "Please select the capital";
            sheet.Range["E12"].Text = "Please select the con tinent";
            sheet.AutoFitColumn(4);
            sheet.AutoFitColumn(5);

            //Style
            sheet.Range["D8:D12"].Style.Font.IsBold = true;
            sheet.Range["D8"].Style.KnownColor = ExcelColors.Color36;
            sheet.Range["D10"].Style.KnownColor = ExcelColors.Color36;
            sheet.Range["D12"].Style.KnownColor = ExcelColors.Color36;
            sheet.Range["E8"].Style.KnownColor = ExcelColors.LightGreen1;
            sheet.Range["E10"].Style.KnownColor = ExcelColors.LightGreen1;
            sheet.Range["E12"].Style.KnownColor = ExcelColors.LightGreen1;

            sheet.SetRowHeight(8, 16);
            sheet.SetRowHeight(10, 16);
            sheet.SetRowHeight(12, 16);
        }
        static void Main(string[] args)
        {
            //Build the workbook
            Workbook workbook = new Workbook();
            workbook.CreateEmptySheets(1);
            Worksheet sheet = workbook.Worksheets[0];
            sheet.GridLinesVisible = false;

            //Write sample data
            CreateSampleData(sheet);
            workbook.SaveToFile("test.xls");
            System.Diagnostics.Process.Start(workbook.FileName);
        }
    }
}                                                                                                                                                                                                                                              

                                                                                                          
Imports Spire.Xls

Module Module1
    Private Sub CreateSampleData(ByVal sheet As Worksheet)
        sheet.Range("D8").Text = "Country"
        'Set the datasource of D9
        sheet.Range("X1").Text = "Lucy"
        sheet.Range("X2").Text = "Bolivia"
        sheet.Range("X3").Text = "Brazil"
        sheet.Range("X4").Text = "Canada"
        sheet.Range("X5").Text = "Chile"
        sheet.Range("X6").Text = "Colombia"
        sheet.Range("X7").Text = "Cuba"
        sheet.Range("X8").Text = "Ecuador"
        sheet.Range("X9").Text = " Salvado"
        sheet.Range("X10").Text = "Guyana"
        sheet.Range("X11").Text = "Jamaicatates"
        sheet.Range("X12").Text = "Mexico"
        sheet.Range("X13").Text = "Nicaragua"
        sheet.Range("X14").Text = "Paraguay"
        sheet.Range("X15").Text = "Peru"
        sheet.Range("X16").Text = "United"
        sheet.Range("X17").Text = "Uruguay"
        sheet.Range("X18").Text = "Venezue"

        'Binding the datasource of D9
        Dim rangeCountry As CellRange = sheet.Range("E8")
        rangeCountry.DataValidation.AllowType = CellDataType.Formula
        rangeCountry.DataValidation.DataRange = sheet.Range("X1:X18")
        rangeCountry.DataValidation.IsSuppressDropDownArrow = False
        rangeCountry.DataValidation.IgnoreBlank = True
        rangeCountry.Activate()
        sheet.HideColumn(sheet.Range("X1").Column)

        sheet.Range("D10").Text = "Capital"
        'Set the datasource of E9
        sheet.Range("Y1").Text = "Buenos Aires"
        sheet.Range("Y2").Text = "La Paz"
        sheet.Range("Y3").Text = "Brasilia"
        sheet.Range("Y4").Text = "Ottawa"
        sheet.Range("Y5").Text = "Santiago"
        sheet.Range("Y6").Text = "Bagota"
        sheet.Range("Y7").Text = "Havana"
        sheet.Range("Y8").Text = "Quito"
        sheet.Range("Y9").Text = "San Salvador"
        sheet.Range("Y10").Text = "Georgetown"
        sheet.Range("Y11").Text = "Kingston"
        sheet.Range("Y12").Text = "Mexico City"
        sheet.Range("Y13").Text = "Managua"
        sheet.Range("Y14").Text = "Asuncion"
        sheet.Range("Y15").Text = "Lima"
        sheet.Range("Y16").Text = "Washington"
        sheet.Range("Y17").Text = "Montevideo"
        sheet.Range("Y18").Text = "Caracas"

        'Binding the datasource of E9
        Dim rangeCapital As CellRange = sheet.Range("E10")
        rangeCapital.DataValidation.AllowType = CellDataType.Formula
        rangeCapital.DataValidation.DataRange = sheet.Range("Y1:Y18")
        rangeCapital.DataValidation.IsSuppressDropDownArrow = False
        rangeCapital.DataValidation.IgnoreBlank = True
        rangeCapital.Activate()
        sheet.HideColumn(sheet.Range("Y1").Column)

        sheet.Range("D12").Text = "Continent"
        'Set the datasource of F9
        Dim rangeContinent As CellRange = sheet.Range("E12")
        rangeContinent.DataValidation.AllowType = CellDataType.Formula
        rangeContinent.DataValidation.Values = New String() {"South America", "North America"}
        rangeContinent.DataValidation.IsSuppressDropDownArrow = False
        rangeContinent.Activate()

        'Set the width of the column
        sheet.Range("E8").Text = "Please select the country "
        sheet.Range("E10").Text = "Please select the capital "
        sheet.Range("E12").Text = "Please select the continent "
        sheet.AutoFitColumn(4)
        sheet.AutoFitColumn(5)

        'Style                                                            
        sheet.Range("D8:D12").Style.Font.IsBold = True
        sheet.Range("D8").Style.KnownColor = ExcelColors.Color36
        sheet.Range("D10").Style.KnownColor = ExcelColors.Color36
        sheet.Range("D12").Style.KnownColor = ExcelColors.Color36
        sheet.Range("E8").Style.KnownColor = ExcelColors.LightGreen1
        sheet.Range("E10").Style.KnownColor = ExcelColors.LightGreen1
        sheet.Range("E12").Style.KnownColor = ExcelColors.LightGreen1
        sheet.SetRowHeight(8, 16)
        sheet.SetRowHeight(10, 16)
        sheet.SetRowHeight(12, 16)
    End Sub

    Sub Main()
        Dim workbook As Workbook = New Workbook()
        workbook.CreateEmptySheet(1)
        Dim sheet As Worksheet = workbook.Worksheets(0)
        sheet.GridLinesVisible = False
        'Writes sample data
        CreateSampleData(sheet)
        workbook.SaveToFile("test.xls")
        System.Diagnostics.Process.Start(workbook.FileName)
    End Sub

End Module