How to convert values of a datatable from string to integer - sql

Question

I'm making a fine calculator in a library system. In it,I need to calculate the fine of a given day. For this,I use a data table to load the fine amounts and then,I need to calculate the total fine amount by adding each fine amount.But I'm having a problem in parsing the fine values which are in string format to integer.Here is a screenshot of the error.
Here is a screenshot of the error.
And here is the code which I used to convert the string values to integer and calculate the total fine.
int sum1 = 0;
int myNum;
String Display;
private void btnNext_Click(object sender, EventArgs e)
{
try
{
if (rbtnToday.Checked == true)
{
DateTime today = DateTime.Today;
Con.Open();
String select_today_query = "SELECT Fine FROM BookReceiveMem WHERE RecDate='" + today + "'";
Sqlda = new SqlDataAdapter(select_today_query, Con);
DataTable Dt = new DataTable();
Sqlda.Fill(Dt);
Con.Close();
foreach (DataRow row in Dt.Rows)
{
myNum = int.Parse(Dt.Columns[0].ToString());
sum1 = sum1 + myNum;
}
Display = sum1.ToString();
MessageBox.Show("Today Fine Amount is= " + Display, "Today Fine Calculation", MessageBoxButtons.OK, MessageBoxIcon.Information);
}
}
Is there any method to solve this problem?

Answer 1

Databases are really good at calculating things like a sum. If Fine is an integer in your database you can get it to sum all the rows and just return that:
SELECT SUM(Fine) As TotalFine
FROM BookReceiveMem
WHERE RecDate = #recDate
Which you could call from code without ever needing a DataTable as follows:
using(var cmd = Con.CreatCommand())
{
cmd.CommandText = "SELECT SUM(Fine) As TotalFine FROM BookReceiveMem WHERE RecDate = #recDate";
cmd.CommandType = CommandType.Text;
cmd.Parameters.Add("#recDate",DateTime.Today);
var result = (int)cmd.ExecuteScalar();
MessageBox.Show("Today Fine Amount is= " + result, "Today Fine Calculation", MessageBoxButtons.OK, MessageBoxIcon.Information);
}
Note that the above uses a Parameterized Query which is much safer than using string concatenation
However, a more direct answer to your question:
myNum = int.Parse(Dt.Columns[0].ToString());
Here you're getting the Column and trying to turn that to an integer. What you actually meant to do was get the row value (and you dont need to Parse it - it's already an integer!)
myNum = (int)row["Fine"];