Solved

An unhandled exception of type 'System.FormatException' occurred in mscorlib.dll

Posted on 2016-10-07
5
59 Views
Last Modified: 2016-10-07
private void TxtMarks1030_TextChanged(object sender, EventArgs e)
        {

            Int32 marks1030 = Convert.ToInt32(TxtMarks1030.Text);

            if (marks1030 >= 101)
            {
                LblGrade1030.Text = "Please enter less than 100";
            }
            else if (marks1030 >= 90)
            {
                LblGrade1030.Text = "A";
            }
            else if (marks1030 >= 80)
            {
                LblGrade1030.Text = "B";
            }
            else if (marks1030 >= 65)
            {
                LblGrade1030.Text = "C";
            }
            else if (marks1030 >= 50)
            {
                LblGrade1030.Text = "D";
            }
            else if (marks1030 >= 40)
            {
                LblGrade1030.Text = "E";
            }
            else
            {
                LblGrade1030.Text = "Fail";
            }
        }
0
Comment
Question by:the student
  • 2
  • 2
5 Comments
 
LVL 33

Accepted Solution

by:
it_saige earned 500 total points
ID: 41834431
This exception occurs because the string being presented to convert is not convertable to an integer; e.g -
using System;

namespace EE_Q28975134
{
	class Program
	{
		static string grade1 = "90";
		static string grade2 = "I am not the number 90";

		static void Main(string[] args)
		{
			GetGrade(grade1);
			Console.WriteLine();
			GetGrade(grade2);
			Console.ReadLine();
		}

		private static void GetGrade(string value)
		{
			try 
			{
				int grade = Convert.ToInt32(value);
				if (grade > 100)
					Console.WriteLine("Please enter a grade less than 100.");
				else
					Console.WriteLine("Your test score - [{0}] produces a grade of: {1}", value, grade >= 90 ? "A" : grade >= 80 ? "B" : grade >= 65 ? "C" : grade >= 50 ? "D" : grade >= 40 ? "D" : "F");
			}
			catch (Exception ex)
			{
				Console.WriteLine("The value entered cannot convert to an integer, grade cannot be calculated.  {0}", ex.Message);
			}
		}
	}
}

Open in new window

Produces the following output -Capture.JPG
To correct you can use a try...catch block as I demonstrated:
private void TxtMarks1030_TextChanged(object sender, EventArgs e)
{
	try
	{
		Int32 marks1030 = Convert.ToInt32(TxtMarks1030.Text);
		if (marks1030 >= 101)
			LblGrade1030.Text = "Please enter less than 100";
		else if (marks1030 >= 90)
			LblGrade1030.Text = "A";
		else if (marks1030 >= 80)
			LblGrade1030.Text = "B";
		else if (marks1030 >= 65)
			LblGrade1030.Text = "C";
		else if (marks1030 >= 50)
			LblGrade1030.Text = "D";
		else if (marks1030 >= 40)
			LblGrade1030.Text = "E";
		else
			LblGrade1030.Text = "Fail";
	}
	catch (Exception)
	{
		LblGrade1030.Text = "Cannot convert grade";
	}
}

Open in new window

Or you could use a different method to convert your field's value, a method that does not throw an exception.  Something like Int32.TryParse.  Since it returns a boolean value that siginifies the conversion was successful, you would change your method to do this:
private void TxtMarks1030_TextChanged(object sender, EventArgs e)
{
	Int32 marks1030;
	if(Int32.TryParse(TxtMarks1030.Text, out marks1030))
	{
		if (marks1030 >= 101)
			LblGrade1030.Text = "Please enter less than 100";
		else if (marks1030 >= 90)
			LblGrade1030.Text = "A";
		else if (marks1030 >= 80)
			LblGrade1030.Text = "B";
		else if (marks1030 >= 65)
			LblGrade1030.Text = "C";
		else if (marks1030 >= 50)
			LblGrade1030.Text = "D";
		else if (marks1030 >= 40)
			LblGrade1030.Text = "E";
		else
			LblGrade1030.Text = "Fail";
	}
	else
	{
		LblGrade1030.Text = "Cannot convert grade";
	}
}

Open in new window


Proof of concept rewriting the above example:
using System;

namespace EE_Q28975134
{
	class Program
	{
		static string grade1 = "90";
		static string grade2 = "I am not the number 90";

		static void Main(string[] args)
		{
			GetGrade(grade1);
			Console.WriteLine();
			GetGrade(grade2);
			Console.ReadLine();
		}

		private static void GetGrade(string value)
		{
			int grade;
			if (int.TryParse(value, out grade))
			{
				if (grade > 100)
					Console.WriteLine("Please enter a grade less than 100.");
				else
					Console.WriteLine("Your test score - [{0}] produces a grade of: {1}", value, grade >= 90 ? "A" : grade >= 80 ? "B" : grade >= 65 ? "C" : grade >= 50 ? "D" : grade >= 40 ? "D" : "F");
			}
			else
			{
				Console.WriteLine("The value entered cannot convert to an integer, grade cannot be calculated.");
			}
		}
	}
}

Open in new window

Now produces a very similar output (minus the exception message ofcourse) -Capture.JPG
-saige-
0
 

Author Comment

by:the student
ID: 41834444
Thank you, it_saige.

It was very helpful now it's working fine. You made my day. This was the part of assignment. thank you again
0
 
LVL 79

Expert Comment

by:David Johnson, CD, MVP
ID: 41834461
Test for null or empty string.and validated input.
 private void TxtMarks1030_TextChanged(object sender, EventArgs e)
        {
            
            if (string.IsNullOrEmpty(TxtMarks1030.Text) == false)
            {
                try
                {
                    Int32 marks1030 = Convert.ToInt32(TxtMarks1030.Text);
                    if (marks1030 >= 101) { LblGrade1030.Text = "Please enter less than 100"; }
                    else if (marks1030 >= 90) { LblGrade1030.Text = "A"; }
                    else if (marks1030 >= 80) { LblGrade1030.Text = "B"; }
                    else if (marks1030 >= 65) { LblGrade1030.Text = "C"; }
                    else if (marks1030 >= 50) { LblGrade1030.Text = "D"; }
                    else if (marks1030 >= 40) { LblGrade1030.Text = "E"; }
                    else { LblGrade1030.Text = "Fail"; }
                }
                catch {
                    LblGrade1030.Text = "You must enter an integer  from 0 to 100";
                }
            }
        }

Open in new window


Yet another method that uses tryparse
using System;
using System.Windows.Forms;

namespace WindowsFormsApplication2
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            LblGrade1030.Text = "Enter an Integer from 0 to 100";
        }

        private void TxtMarks1030_TextChanged(object sender, EventArgs e)
        {
            Int32 marks1030;
            LblGrade1030.Text = "Enter an Integer from 0 to 100";
            if (int.TryParse(TxtMarks1030.Text, out marks1030))
            {

                if (marks1030 >= 101) { LblGrade1030.Text = "Please enter less than 100"; }
                else if (marks1030 >= 90) { LblGrade1030.Text = "A"; }
                else if (marks1030 >= 80) { LblGrade1030.Text = "B"; }
                else if (marks1030 >= 65) { LblGrade1030.Text = "C"; }
                else if (marks1030 >= 50) { LblGrade1030.Text = "D"; }
                else if (marks1030 >= 40) { LblGrade1030.Text = "E"; }
                else { LblGrade1030.Text = "Fail"; }
            }

        }
    }

}

Open in new window

0
 
LVL 79

Expert Comment

by:David Johnson, CD, MVP
ID: 41834462
Should have refreshed the page first
2
 

Author Comment

by:the student
ID: 41834467
Thanks David Johnson
0

Featured Post

Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
Turn on intranet settings 1 42
free scanner TWAIN can be operated with a Web application 9 41
C# parent child form 5 19
VB.Net - Windows UserName index and length error 4 24
Microsoft Reports are based on a report definition, which is an XML file that describes data and layout for the report, with a different extension. You can create a client-side report definition language (*.rdlc) file with Visual Studio, and build g…
This article is for Object-Oriented Programming (OOP) beginners. An Interface contains declarations of events, indexers, methods and/or properties. Any class which implements the Interface should provide the concrete implementation for each Inter…
This Micro Tutorial will teach you how to censor certain areas of your screen. The example in this video will show a little boy's face being blurred. This will be demonstrated using Adobe Premiere Pro CS6.
Internet Business Fax to Email Made Easy - With  eFax Corporate (http://www.enterprise.efax.com), you'll receive a dedicated online fax number, which is used the same way as a typical analog fax number. You'll receive secure faxes in your email, f…

863 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

27 Experts available now in Live!

Get 1:1 Help Now