System.FormatException: Input string was not in a correct format - asp.net

Question

In the following code, when I try to add an Item to an ASP DropDownList, System.FormatException: Input string was not in a correct format, is thrown.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
public partial class ScheduleExam : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
String connection = System.Configuration.ConfigurationManager.ConnectionStrings["TYCConnection"].ConnectionString;
String branch = Request.Form["ctl00$ctl00$MainContent$AdminMainContent$BranchDropDownList"];
if (!String.IsNullOrWhiteSpace(branch))
{
if (!branch.Equals("00"))
{
SqlConnection sqlConn = new SqlConnection(connection);
String semQuery = "select totalSem from branchTable where branchId='" + branch + "'";
SqlCommand semCommand = new SqlCommand(semQuery, sqlConn);
sqlConn.Open();
SqlDataReader semReader = semCommand.ExecuteReader();
semReader.Read();
int totalSem = Int32.Parse(semReader["totalSem"].ToString());
SemesterDropDownList.Items.Clear();
SemesterDropDownList.Enabled = true;
//ListItem list = new ListItem("Select");
SemesterDropDownList.Items.Add(new ListItem("select"));
for (int sem = 1; sem <= totalSem; sem++)
{
//SemesterDropDownList.Items.Add(sem.ToString());
}
sqlConn.Close();
}
else
{
SemesterDropDownList.Items.Clear();
SemesterDropDownList.Enabled = false;
//SemesterDropDownList.Items.Add("First Select Branch");
}
}
else
{
SemesterDropDownList.Enabled = false;
//SemesterDropDownList.Items.Add("First Select Branch");
}
}
protected void RegisterButton_Click(object sender, EventArgs e)
{
}
}
However, when I comment all such lines there is no exception thrown.
What could be the problem and its possible solution?

Answer 1

Instead of
int totalSem = Int32.Parse(semReader["totalSem"].ToString());
try
int totalSem;
Int32.TryParse(semReader["totalSem"].ToString(),totalSem);
and if that takes care of the exception then look into addressing the issues with that field.