Struggling with simple calculations

Question

User-1874496678 posted

Hi

I have a form which serves as basket for donations. It is working fine but would like to do simple calculations on total amount, but struggling with it.

I get total from query

 sql = "SELECT Sum(Cart.Amount) AS TotalAmount FROM Cart WHERE Cart.SessionId = @0";
 var Total = db.Query(sql, sessionid);

which is then displayed as table footer.

           @foreach (var item in Total)
            {
            <tr >
                <td style=" border-top:2px solid #C2EBFF;" >&nbsp;</td>
                <td style=" border-top:2px solid #C2EBFF;" >Total: </td>
                <td style=" border-top:2px solid #C2EBFF;" >£@item.TotalAmount</td>
 
            </tr>
            }

This is ok. Now I am trying to display simple calculations regarding difference in transaction charges between Debit (e.g. multiply by 0.025) and Credit card (e.g. multiply by 0.3) but getting errors if I perform any calculations on TotalAmount.

Any help is much appreciated.

Also I am not sure why I have to use a loop with var Total, as only one record is returned, if I use QuerySingle, I get error. any simple explanation would help my understanding.

Regards

Hamid

Answer 1

User-821857111 posted

You should post the errors you get. It will help to diagnose what you are doing wrong.

Also I am not sure why I have to use a loop with var Total, as only one record is returned, if I use QuerySingle, I get error. any simple explanation would help my understanding.

Ideally, you should use QueryValue, as that is designed to cater for retrieving scalar values:

sql = "SELECT Sum(Cart.Amount) AS TotalAmount FROM Cart WHERE Cart.SessionId = @0";
var TotalAmount = db.QueryValue(sql, sessionid);

<tr >
   <td style=" border-top:2px solid #C2EBFF;" >&nbsp;</td>
   <td style=" border-top:2px solid #C2EBFF;" >Total: </td>
   <td style=" border-top:2px solid #C2EBFF;" >£@TotalAmount</td>

No looping - just a single value. QuerySingle is for dealing with single row results.

If you want to perform mathematical calculations on TotalAmount, you may well have to cast it to a decimal.

Answer 2

User325035487 posted

item.TotalAmount is a dynamic data type
do this. 

var Total = db.QueryValue(sql, sessionid);
if(Total!=null){
var totalvalue = (float)Total;
//now u can do calculations on totalvalue
}