How to Insert null from TextBox to integer Field

[nabil122]

I have a text box and datetime where can i enter an integer . I wish to store this in a SQL Server Database. If i enter then I would store a NULL. However if the text box is left blank, I get an error Input string was not in a correct format. How can I work around this, and get the null into the db?

this Code in method

public void Add_ItemSeasonalPrices(string ItemCode, DateTime FromDate, DateTime ToDate, decimal WholeSaleForFirstUnit, decimal WholeSaleForSecondUnit, decimal WholeSaleForThirdUnit)
    {
        DAL.DataAccessLayer DAL = new DAL.DataAccessLayer();
        DAL.open();
        SqlParameter[] param = new SqlParameter[22];
        param[0] = new SqlParameter("@ItemCode", SqlDbType.NVarChar, 25);
        param[0].Value = ItemCode;
 
        param[1] = new SqlParameter("@FromDate", SqlDbType.DateTime);
        param[1].Value = FromDate;
 
 
        param[2] = new SqlParameter("@ToDate", SqlDbType.DateTime);
        param[2].Value = ToDate;
 
 
        param[3] = new SqlParameter("@WholeSaleForFirstUnit", SqlDbType.Decimal);
        param[3].Value = WholeSaleForFirstUnit;
 
 
        param[4] = new SqlParameter("@WholeSaleForSecondUnit", SqlDbType.Decimal);
        param[4].Value = WholeSaleForSecondUnit;
 
 
        param[5] = new SqlParameter("@WholeSaleForThirdUnit ", SqlDbType.Decimal);
        param[5].Value = WholeSaleForThirdUnit;
 DAL.ExecuteCommand("Add_ItemSeasonalPrices", param);
        DAL.close();
    }

and this Code in btnSave

Item.Add_ItemSeasonalPrices(txt_ItemCode.Text, Convert.ToDateTime(FromDate.Text), Convert.ToDateTime(ToDate.Text), Convert.ToDecimal(txt_WholeSaleForFirstUnit.Text), Convert.ToDecimal(txt_WholeSaleForSecondUnit.Text),
                                            Convert.ToDecimal(txt_WholeSaleForThirdUnit.Text);