Export data from textbox to excel without using database

Question

Hi,

I want to export data from textbox to excelsheet without using database or gridview.

I have created like this - 

Microsoft.Office.Interop.Excel.Application xlApp = new Microsoft.Office.Interop.Excel.Application();

        Microsoft.Office.Interop.Excel.Workbook xlWB;

        Microsoft.Office.Interop.Excel.Worksheet xlWS;

        Microsoft.Office.Interop.Excel.Range xlRng;

        string workbookPath = "D:\\New Microsoft Office Excel Worksheet.xls";

protected void btnexcel_Click(object sender, EventArgs e)

    {

        xlApp.Workbooks.Open(workbookPath, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value);

        int colIndex = 0;

        string addTNumbers = txtname.Text;

        xlWS.Cells[1, 1] = addTNumbers;

        //Save the file to where you specified

        xlWB.Save();

        xlApp.Visible = true;         

       

    }

but i am getting error on "xlWS.Cells[1, 1] = addTNumbers;" line that object reference not set to an instance.

Please tell me, how to get this.