I want to write the event handler method button1_Click to calculate whether student’s Grade is “PASS” or “FAIL”. The student passes the course if the total score is greater than or equal to 50. The total score is Midterm(textbox1) + Final(textbox2) scores. However, teacher can give student Extra Credit(checkbox1) which is worth 10 points. The result will present in the textBox3
Here's my code:
private void button1_Click(object sender, EventArgs e)
{
int midtermInt = int.Parse(textBox1.Text);
int finalInt = int.Parse(textBox2.Text);
if (checkBox1.Checked)
{
if ((midtermInt + finalInt) + 10 >= 50)
{
grade.Text = "PASS";
}
else if ((midtermInt + finalInt) + 10 < 50)
{
grade.Text = "FAIL";
}
}
else if (!checkBox1.Checked)
{
if ((midtermInt + finalInt) >= 50)
{
grade.Text = "PASS";
}
else if ((midtermInt + finalInt) < 50)
{
grade.Text = "FAIL";
}
}
When I run it, it says "Inut string was not in a correct format.. :(
I'm very new to C# please advise me if my code is wrong anywhere
The input will only be integers never texts..
You should use int.TryParse insted int.Parse, it's check is specified string is in correct format.
You code may looks like this:
int midtermInt;
if (!int.TryParse(textBox1.Text, out midtermInt))
{
labelError.Text = "Icorrect value in field 'textBox1'".
return;
}
If you type non-numeric characters in your textbox and try to parse the text, it will throw you this exception. Try trimming the input and definitely consider adding UI validation to your forms.
You can add checking, if text in text box is in correct format in TextChanged event:
private void textBox_TextChanged(object sender, EventArgs e)
{
int val;
if (textBox.Text.Length == 0 || !int.TryParse(textBox.Text, out val))
tsPassingScore.Text = "0";
}
And in your click you can check if there is number in textBox again with int.TryParse
Also you can improve your code:
If final summ is not bigger then 50 - it is automatically smaller! And it would be more readable, if you introduce extra variable - for teachers extra credit:
int extraCredit = checkBox1.Checked ? 10 : 0;
int finalScore = midtermInt + finalInt + extraCredit;
if (finalScore >= 50)
grade.Text = "PASS";
else
grade.Text = "FAIL";
Related
I'm creating a calculator and I want to add validation code in it, so that if anything besides numbers is entered, an error message appears.
private void button4_Click(object sender, EventArgs e)
{
int R = Convert.ToInt32(textBox1.Text);
int I = Convert.ToInt32(textBox2.Text);
int number2;
if (int.TryParse(textBox1.Text, out number2))
{
int E = R - I;
textBox3.Text = E.ToString();
}
else
{
textBox2.Text = ("value entered is not whole number");
}
}
This is the code I am trying to use but it comes up with an error message when I enter a non-numeric value.
You are calling Convert.ToInt32 method before TryParse and that causes the exception. Don't do that, do the validation with TryParse.
private void button4_Click(object sender, EventArgs e)
{
int R, I;
if (int.TryParse(textBox1.Text, out R) &&
int.TryParse(textBox2.Text, out I))
{
int E = R - I;
textBox3.Text = E.ToString();
}
else
{
MessageBox.Show("You have entered an invalid value!");
}
}
Also you might consider using more descriptive variable names instead of E, R, I...
private void button4_Click(object sender, EventArgs e)
{
int R, I;
if (int.TryParse(textBox1.Text, out R)
&& int.TryParse(textBox2.Text, out I))
{
int E = R - I;
textBox3.Text = E.ToString();
}
else { textBox3.Text = ("value entered is not whole number"); }
}
Make sure you try to parse the strings into ints with TryParse always, rather than just converting immediately... if there are letters, the conversion fails.
private void button4_Click(object sender, EventArgs e)
{
int number1;
int number2;
if (int.TryParse(textBox1.Text, out number1) && int.TryParse(textBox2.Text, out number2))
{
//do your thang (subtraction, assigning the result to TextBox3)
//return
}
else
{
MessageBox.Show("Oh no you entered something that's not an int!");
}
}
I might also add that making the value of one of your input text boxes "Value entered is not a whole number" is kind of a weird UI experience. I'd mark the textbox in red or pop up a message box or something instead, leaving the entered value in the box, in case it was some really long number like 879320!78 where they accidentally entered a weird symbol or something.
I'm building an application to transform fractions to percentages. I want it so that if I edit the text in the fraction it refreshes and recalculates the percentage.
When I test it, the first time I edit the fraction it doesn't error and works fine but the second time I change something in the fraction it errors. I get this error
An unhandled exception of type System.ArgumentOutOfRangeException occurred in mscorlib.dll
What can I do to fix this?
I'm fairly new to C# so try to dumb it down if at all possible.
Additional information: Index and length must refer to a location within the string."
Here's what I have so far:
private void fractionNumerator_KeyPress(object sender, KeyPressEventArgs e)
{
if (!(char.IsNumber(e.KeyChar) || ((e.KeyChar) == Convert.ToChar(Keys.Back))))
{
e.Handled = true;
}
else
{
if (!((fractionNumerator.Text == "") && (fractionDenominator.Text == "")))
{
if ((e.KeyChar == Convert.ToChar(Keys.Back)))
{
string numer = (fractionNumerator.Text.Substring(0, (fractionNumerator.Text.Length) - 1));
string denom = (fractionDenominator.Text);
outputPercentage.Text = (((((Convert.ToDouble(numer) / Convert.ToDouble(denom)) * 100).ToString()).Substring(0, 6)) + "%");
}
else
{
string numer = ((fractionNumerator.Text) + e.KeyChar.ToString());
string denom = (fractionDenominator.Text);
outputPercentage.Text = (((Convert.ToDouble(numer)/Convert.ToDouble(denom)*100).ToString()).Substring(0, 6));
}
}
}
}
private void fractionDenominator_KeyPress(object sender, KeyPressEventArgs e)
{
if (!(char.IsNumber(e.KeyChar) || ((e.KeyChar) == Convert.ToChar(Keys.Back))))
{
e.Handled = true;
}
else
{
if (!((fractionNumerator.Text == "") && (fractionDenominator.Text == "")))
{
if ((e.KeyChar == Convert.ToChar(Keys.Back)))
{
string denom = (fractionDenominator.Text.Substring(0, (fractionDenominator.Text.Length) - 1));
string numer = (fractionNumerator.Text);
outputPercentage.Text = (((((Convert.ToDouble(numer) / Convert.ToDouble(denom)) * 100).ToString()).Substring(0, 6)) + "%");
}
else
{
string denom = ((fractionDenominator.Text) + e.KeyChar.ToString());
string numer = (fractionNumerator.Text);
outputPercentage.Text = (((Convert.ToDouble(numer) / Convert.ToDouble(denom) * 100).ToString()).Substring(0, 6));
}
}
}
}
From the code you provided i can tell that one of your Substring methods throws this exception. So its probably has invalid second parameter (its either less than 0 or higher than string length). Check msdn for details: http://msdn.microsoft.com/ru-ru/library/aka44szs%28v=vs.110%29.aspx
As mentioned in the comments by mike z, you should use format strings instead of Substring method to format your output. For example doubleValue.ToString("#.####") will return 4 digits of fractional part.
Use yourDoubleExpr.ToString("P4") to convert from number to percentage string. The multiplication by 100.0 is automatic.
Your problem was that cases like (3.0 / 4.0).ToString() lead to a short string, like "0.75", and you cannot take out a .Substring of length 6 from that.
I want to auto format a text entered in a textbox like so:
If a user enters 2 characters, like 38, it automatically adds a space. so, if I type 384052
The end result will be: 38 30 52.
I tried doing that, but it's ofr some reason right to left and it's all screwed up.. what I'm doing wrong?
static int Count = 0;
private void packetTextBox_KeyPress(object sender, KeyPressEventArgs e)
{
Count++;
if (Count % 2 == 0)
{
packetTextBox.Text += " ";
}
}
Thanks!
It's much nicer if you just let the user type and then modify the contents when the user leaves the TextBox.
You can do that by reacting not to the KeyPress event, but to the TextChanged event.
private void packetTextBox_TextChanged(object sender, EventArgs e)
{
string oldValue = (sender as TextBox).Text.Trim();
string newValue = "";
// IF there are more than 2 characters in oldValue:
// Move 2 chars from oldValue to newValue, and add a space to newValue
// Remove the first 2 chars from oldValue
// ELSE
// Just append oldValue to newValue
// Make oldValue empty
// REPEAT as long as oldValue is not empty
(sender as TextBox).Text = newValue;
}
On TextChanged event:
int space = 0;
string finalString ="";
for (i = 0; i < txtbox.lenght; i++)
{
finalString = finalString + string[i];
space++;
if (space = 3 )
{
finalString = finalString + " ";
space = 0;
}
}
I used
int amount;
private void textBox1_TextChanged(object sender, EventArgs e)
{
amount++;
if (amount == 2)
{
textBox1.Text += " ";
textBox1.Select(textBox1.Text.Length, 0);
amount = 0;
}
}
Try this..
on TextChanged event
textBoxX3.Text = Convert.ToInt64(textBoxX3.Text.Replace(",", "")).ToString("N0");
textBoxX3.SelectionStart = textBoxX3.Text.Length + 1;
I am trying to have a multi line textbox that when you type in it streams it to the label, BUT the label has to have a max length of 15 so like once it reaches 15 characters in the textbox it should start overwriting the label since it reached it's max length
thanks to anyone who can help
Add onchange event on text box :
if (textBox1.Text.Length<=15)
{
label1.Caption=textBox1.Text;
}
For example
I'm not sure what kind of overwriting You want to achieve.
There are at least three methods you can use:
displaying always the last 15 characters from the textbox, as described in the Olivier's answer
clearing the label's text each 15 characters inserted and start filling in the label over again, you can use this code to achieve this:
private void textBox1_TextChanged(object sender, EventArgs e)
{
String text = textBox1.Text.Replace("\r\n", "|");
int startIndex = ((text.Length - 1) / 15) * 15;
label1.Text = text.Substring(Math.Max(0, startIndex));
}
you can also overwrite char by char when text length is over 15 characters, however, I suppose it's not what you would like to achieve, because it would cause a mess in the textbox ;), however, it can be used as a kind of visual effect :). If you want code snippet for this, let me know :).
Update
Here's the code for the third overwriting method:
String lastText = "";
private void textBox1_TextChanged(object sender, EventArgs e)
{
String textBoxText = textBox1.Text.Replace("\r\n", "|");
if (textBoxText.Length > lastText.Length)
{
int charIndex = (textBoxText.Length - 1) % 15;
if (charIndex >= 0)
{
label1.Text = label1.Text.Insert(charIndex, textBoxText.Substring(textBoxText.Length - 1));
if (charIndex < textBoxText.Length - 1)
{
label1.Text = label1.Text.Remove(charIndex + 1, 1);
}
}
}
else
{
int charIndex = textBoxText.Length % 15;
if (textBoxText.Length >= 15)
{
label1.Text = label1.Text.Insert(charIndex, textBoxText[textBoxText.Length - 15].ToString());
if (charIndex < textBoxText.Length - 1)
{
label1.Text = label1.Text.Remove(charIndex + 1, 1);
}
}
else
{
label1.Text = label1.Text.Remove(label1.Text.Length - 1, 1);
}
}
lastText = textBoxText;
}
Add a handler to the TextChanged event of the TextBox that sets the Label's content based on the text. E.g. (untested, might have your concept wrong or be off by one somewhere)
int startIndex = Math.Max(0, myTextBox.Text.Length - 15);
int endIndex = Math.Min(myTextBox.Text.Length - 1, startIndex);
myLabel.Text = myTextBox.Text.Substring(startIndex, endIndex - startIndex);
Also, though it doesn't change your question/answer, you might want to look at using a TextBlock instead of a Label. It allows things like line wrapping. See some of the differences here: http://joshsmithonwpf.wordpress.com/2007/07/04/differences-between-label-and-textblock/ (in WPF, should be similar whatever you're doing, though)
My solution always displays the last 15 characters in the label
private void textBox1_TextChanged(object sender, EventArgs e)
{
string s = textBox1.Text.Replace("\r\n", "|");
int length = s.Length;
if (length > 15) {
label1.Text = s.Substring(length - 15);
} else {
label1.Text = s;
}
}
I also replace the line-breaks with |. Since your textbox is in multiline mode, line-breaks are entered when you hit <Enter>.
I have the following code in my TextBox leave event:
private void txtAmount_Leave(object sender, EventArgs e)
{
int x = Convert.ToInt32(txtAmount.Text);
double res = (double)x / 100;
txtAmount.Text = "$" + res.ToString();
}
But if move back to the previous control by hitting Shift+Tab and again moving back to the same textbox and then trying to move to other the form is getting closed automatically. Why does this happen?
The call to Convert.ToInt32() is probably throwing an exception, likely due to being unable to convert the string in your TextBox to an integer. Convert.ToInt32() can throw the following exceptions (descriptions from MSDN):
FormatException - value does not consist of an optional sign followed by a sequence of digits (0 through 9).
OverflowException - value represents a number that is less than Int32.MinValue or greater than Int32.MaxValue.
It's likely a FormatException, thrown when you leave the TextBox after the $ is prepended to your string, or after you enter any non-numeric characters (letters, etc). To fix this, you have a couple of options:
Add a try / catch block around your code to handle any exceptions.
Use Int32.TryParse() instead of Convert.ToInt32().
Add some code that will prevent non-numeric characters from being entered in your TextBox
Here's an improved version of your event handler:
private void txtAmount_Leave(object sender, EventArgs e)
{
string toParse = txtAmount.Text.TrimStart('$');
int parsed;
if (Int32.TryParse(toParse, out parsed))
{
double res = (double)parsed / 100;
txtAmount.Text = "$" + res.ToString();
}
}
The first time you leave this textbox, its contents will be changed to "$123" (for example). The second time you leave, trying to convert that to int will throw an exception.
You could use the overload of TryParse that takes a NumberStyle, something like this, assuming your goal is to just show a currency value with no decimal places.
double number;
if (double.TryParse(txtAmount.Text, NumberStyles.Currency, CultureInfo.CurrentUICulture, out number))
{
txtAmount.Text = number.ToString("C0");
}
else
{
MessageBox.Show("Could not convert.");
}
After reading #Donut's comment on his answer, I am not sure what your goal is. If you'd like to truncate the cents off but still show the ".00", you can do this:
txtAmount.Text = ((int)number).ToString("C");
Or do this, which will round:
txtAmount.Text = (Convert.ToInt32(number)).ToString("C");
If this does not help, please clarify and let us know what you are trying to accomplish.
Try this:
private void txtAmount_Leave(object sender, EventArgs e)
{
if (!String.IsNullOrEmpty(txtAmount.Text) && txtAmount.Text.StartsWith("$"))
txtAmount.Text = txtAmount.Text.Substring(1);
int x = Convert.ToInt32(txtAmount.Text);
double res = (double)x / 100;
txtAmount.Text = "$" + res.ToString();
}
Check the txtAmount.Text for the $ sign, before trying to convert it to an int. If the $ sign is present, strip it out, and convert the rest of the input to an int.
Also, you might want to use the Int32.TryParse method, as that will help you figuring out whether the entered text can be converted into an int or not.
You may want to change your code to remove the $ before working with the number:
private void txtAmount_Leave(object sender, EventArgs e)
{
int x = 0;
int.TryParse(txtAmount.Text.Replace("$", string.Empty), out x);
double res = (double)x / 100;
txtAmount.Text = "$" + res.ToString();
}
I got the solution
private void txtAmount_Leave(object sender, EventArgs e)
{
string strAmnt = string.Empty;
strAmnt = txtAmount.Text;
if (strAmnt.Contains(".") && !strAmnt.Contains("$"))
{
txtAmount.Text = "$" + strAmnt;
while (txtAmount.Text.Length - txtAmount.Text.IndexOf(".") <= 2)
{
txtAmount.Text += "0";
}
}
else
if (strAmnt.Contains("$") && !strAmnt.Contains("."))
{
Int64 amnt = 0;
strAmnt = strAmnt.Replace("$", "");
try
{
amnt = Convert.ToInt64(strAmnt);
double amt = (double)amnt / 100;
txtAmount.Text = "$" + amt.ToString();
}
catch (FormatException ie)
{
MessageBox.Show("Invalid Format");
}
}
else
if (!strAmnt.Contains(".") && !strAmnt.Contains("$"))
{
try
{
int x = Convert.ToInt32(txtAmount.Text);
double res = (double)x / 100;
txtAmount.Text = "$" + res.ToString();
while (txtAmount.Text.Length - txtAmount.Text.IndexOf(".") <= 2)
{
txtAmount.Text += "0";
}
}
catch (FormatException ie)
{
MessageBox.Show("InvalidFormat");
}
}
while (txtAmount.Text.Length - txtAmount.Text.IndexOf(".") <= 2)
{
txtAmount.Text += "0";
}
}