I've found different help through this website but still can't seem to convert a string to int. I've tried many different ways. Here are two of them. On button_click I need to read the textboxes and convert them to int so I can perform standard logic on them. (a > b functions). Below the first section is what I'm using to force the use of numbers during entry into the text boxes.
private void write_button_Click(object sender, EventArgs e)
{
int mat_od1 = int.Parse(matod_box.Text); //Input string in wrong format.
int mat_id1 = int.Parse(matid_box.Text);
int fod1 = int.Parse(fod_box.Text);
int fid1 = int.Parse(fid_box.Text);
int hp1 = int.Parse(hp_box.Text);
//This next section is just to show something else I've tried.
decimal mat_od = Convert.ToDecimal(matod_box.Text); //Same error.
decimal mat_id = Convert.ToDecimal(matid_box.Text);
decimal fod = Convert.ToDecimal(fod_box.Text);
decimal fid = Convert.ToDecimal(fid_box.Text);
decimal hp = Convert.ToDecimal(hp_box.Text);
decimal pass_od = mat_od;
}
private void fod_box_TextChanged(object sender, EventArgs e)
{
try
{
int numinput = int.Parse(fod_box.Text);
if (numinput < 1 || numinput > 500)
{
MessageBox.Show("You must enter a number between 0 and 500.");
}
}
catch (FormatException)
{
MessageBox.Show("You need to enter a number.");
fod_box.Clear();
}
Any help would be appreciated.
instead of int.Parse() you should use int.TryParse(string,out int)
this way you would be able to chek the output and decide wether the string was correctly parsed or not
int i;string s="";
if(int.TryParse(s,out i))
{
//use i
}
else
{
//show error
}
The int.parse conversion should work, as in this sample:
string s = "111";
int i;
if (int.TryParse(s, out i))
{
Console.Write(i);
}
else
{
Console.Write("conversion failed");
}
Are you sure you actually provide legal input for your ints? In any case, you should use TryParse like I did in my sample. Theres no need to use try..catch where you can use boolean methods provided by the framework, which will get you the same result..
All depends on what you are allowing to be put in the text box.
If it might not be a string that can be converted to an integer, including blank, then something like
int value;
if (int.TryParse(SomeString, out value)
{
// it is an int
}
else
{
// it's not an int, so do nothing raise a message or some such.
}
In addition to using Int32.TryParse in the button Click event handler as others have pointed out, you need to be careful what you're doing in the TextBox Changed event handler. You're code here is flawed:
private void fod_box_TextChanged(object sender, EventArgs e)
{
try
{
int numinput = int.Parse(fod_box.Text);
...
}
catch (FormatException)
{
MessageBox.Show("You need to enter a number.");
fod_box.Clear();
}
Calling foo_box.Clear() will clear any text from the textbox, calling the TextChanged handler to be executed again (unless the TextBox was already empty). So if you enter a non-numeric value, your message box will be displayed twice - the first time when it attempts to parse your non-numeric value, the second time when it attempts to parse an empty string as a result of the call to Clear().
In general, I'd avoid doing validation in the Changed event handler.
Related
I am trying to make a 'guess the number' game for a task in uni and I'm stuck on (what I think) is a parsing issue.
It doesn't show up any errors before I run the program but when it gets to a certain point (after clicking the message box it quits and throws up possible errors and solutions).
I did want to try and fix this myself and I did search everywhere for this but it's not giving me an exact error so I'm a bit stuck on what to search for.
I've included the code below and a link to the screenshot of the error.
Many thanks, Rob
screen shot link : screenshot
private void btnGenerate_Click(object sender, EventArgs e)
{
Random gen = new Random();
int randNumber = gen.Next(1, 1000);
lblWelcome.Text = ("");
btnGenerate.Visible = false;
MessageBox.Show("The computer has picked a number and stored it, please continue and guess the number");
txtbxInputNumber.Visible = true;
int guess = int.Parse(txtbxInputNumber.Text);
while (guess != randNumber)
{
if (guess < randNumber)
{
MessageBox.Show("Try higher");
}
else
{
MessageBox.Show("Try lower");
}
}
}
private void Form1_Load(object sender, EventArgs e)
{
}
You should TryParse your input from the user, not always this can be valid number
int guess = 0;
int.TryParse(txtbxInputNumber.Text, out guess);
You can show an error if you want so he knows that he made an mistake
int guess = 0;
if(!int.TryParse(txtbxInputNumber.Text, out guess))
{
//show error message
return; // quit the method
}
As I look at the screenshot, your txtbxInputNumber.Text is empty! Thats not a valid Int.
You should use, int.TryParse()
int guess;
if(int.TryParse(txtbxInputNumber.Text, out guess))
{
// the guess is a valid int!
}
else
{
// the guess is not a valid int!
}
Due to the input string being blank, the parse does not recognise it as a number, you should add a condition
int guess = int.Parse(txtbxInputNumber.Text == "" ? "0" : txtbxInputNumber.Text);
This is the same as using an if, though an if statement has the bonus that you can return an error
if(txtbxInputNumber.Text == "")
{
MessageBox.Show("Try higher");
return;
}
else
{
int guess = int.Parse(txtbxInputNumber.Text);
}
You could also restrict the input to number so that it will automatically have a number in it
The other option is to use a TryParse, in which case guess must be instantiated first as it is required as an out parameter
It throws an exception because the input is not a number. Use Int32.TryParse instead of Int32.Parse.
int guess;
if (!Int32.TryParse(txtbxInputNumber.Text, out guess))
MessageBox.Show("Enter a number");
The problem is that the txtInputBox value is null when you try to enter the loop. Place the inputbox line inside the while loop and add a check for not null. Should work then something like this:
int guess = 0;
while (guess != randNumber)
{
if !string.IsNullOrEmpty(txtbxInputNumber.Text)
{
guess = int.Parse(txtbxInputNumber.Text);
if (guess < randNumber)
{
MessageBox.Show("Try higher");
}
else
{
MessageBox.Show("Try lower");
}
}
}
.
Instead of 'int.Parse' try with 'int.TryParse'.
int guess ;
//int guess = int.Parse(txtbxInputNumber.Text); //Instead of this
int.TryParse(txtbxInputNumber.Text, out guess ); //use this
I have an application with four text boxes. I want user to be able to enter a value in the first three text boxes. The fourth will give the result (box1 + box2 + box3) / 3.
My textboxes look like this.
private void rBox_1_PreviewTextInput(object sender, TextCompositionEventArgs e)
{
CheckIsNumber(e);
}
And a function to let user enter only digits.
private void CheckIsNumber (TextCompositionEventArgs e)
{
int result;
if (!int.TryParse(e.Text, out result))
{
e.Handled = true;
}
}
The problem is I don't know how to convert and store a value from each textbox in an int.
I've created a null int value to store. In public MainWindow().
int box1_value;
And for function I did this.
public static int GetNumber (string arg)
{
int number = Int32.Parse(arg);
return number;
}
When I'm trying to apply this function this way, nothing happens. Program won't start, no errors, though.
public MainWindow()
{
InitializeComponent();
int box1_value = GetNumber(rBox_1.Text);
}
Remove the
int box1_value = GetNumber(rBox_1.Text);
from your mainwindow constructor.
You're parsing a string.Empty value to int in which the compiler will automatically halt during compilation. Hence your awkward error.
Create a new function called Calculate for calculating your values
private void Calculate()
{
if(string.IsNullOrEmpty(rBox_1.Text) ||
string.IsNullOrEmpty(rBox_2.Text) ||
string.IsNullOrEmpty(rBox_3.Text))
return;
var box1 = GetNumber(rBox_1.Text);
var box2 = GetNumber(rBox_2.Text);
var box3 = GetNumber(rBox_3.Text);
rBox_4.Text = ((box1 + box2 + box3)/3).ToString();
}
You have 2 options for adding the Calculate function:
add it in each rBox_1_PreviewTextInput function as follows:
if(e.Handled)
{
Calculate();
}
or create a button (named button1)
private void button1_Click(object sender, EventArgs e)
{
Calculate();
}
Some Comments: why the string.IsNUllOrEmpty in Calculate?
-> Your GetNumber function does not catch any false string values like Empty. Or you work with tryparse in the GetNumber function or you catch the empty values before you go into the function.
Try using TryParse Method :
int number = Int32.Parse(arg); /*Instead of this line in your code use below.*/
A possible duplicate thread
I would Suggest that you should Add validation to your 1st 3 Test-boxes using PreviewTextInput in that way, you do not have to try parse int in your c# code and will reduce the chance of errors in your code
I have a problem with my textbox. I wanted that one can manually set the interval of the x- and y-axis for a chart in the GUI over two textboxes. That works but when I type a char in or when I typed an int in and delete it, the program crashes immediately and I get a System.FormatException (without clicking the button to accept the changes). How can I solve it that one can just type in different signs without immediately crashing the program? My code below:
public void textBox2_TextChanged(object sender, EventArgs e)
{
x_axis_num = Convert.ToInt32(xAxisBox.Text, usC);
}
private void yAxisBox_TextChanged(object sender, EventArgs e)
{
y_axis_num = Convert.ToInt32(yAxisBox.Text);
}
That gets passed to another event:
chart1.ChartAreas[0].AxisX.Interval = x_axis_num;
chart1.ChartAreas[0].AxisY.Interval = y_axis_num;
In the line x_axis_num = Convert.ToInt32(xAxisBox.Text, usC);, you are taking whatever is in the text box and try to convert it to an integer value.
What do you think the conversion of "Hey, I'm not a number!" will do? It will crash horribly, basically because that text is not, and never will be, a number.
Instead, you can use the Int.TryParse method which will take any text and TRY to convert it to a number.
If the conversion is successful, then no problem. If it was not successful, then you get a false value on a flag indicating the text could not be converted.
Example:
int number;
bool result = Int32.TryParse(YourTextBox.Text, out number);
If the conversion is successful, then number has the value, otherwise, result is false so do something like this then:
if(result)
{
xAxisBox.Text = number.ToString();
x_axis_num = number;
}
else
{
xAxisBox.Text = string.Empty;
// Be careful here with what you set.
// This is the value you will set when the Text box has a non numeric value!
x_axis_num = 0;
}
So I'm trying to create a validating event that makes sure a textbox isn't empty and that the number entered doesn't exceed 2000. I've posted what I have but every time I run it I get a message that the exception wasn't handled because the "kwh = decimal.Parse(khtextBox.Text)" input is not in the correct format. The way I have it, the validating works if the number exceeds 2000, but not if the textbox is blank. What am I doing wrong? Also new to programming so please explain like you're talking to a 3 year old! Thanks :)
private void khtextBox1_Validating(object sender, CancelEventArgs e)
{
decimal kwh;
kwh = decimal.Parse(khtextBox1.Text);
bool blank = false;
if (blank)
{
MessageBox.Show("Please enter a valid number.");
}
if (kwh > 2000)
{
MessageBox.Show("Kilowatt-Hours cannot exceed 2000.");
e.Cancel = true;
}
}
Try using the decimal.TryParse method, which try to convert the string to a decimal and returns a bool value if the conversion succeed, for sample:
decimal kwh;
if (!decimal.TryParse(khtextBox1.Text, out kwh)) // check if the conversion has failed
{
MessageBox.Show("Please enter a valid number.");
e.Cancel = true;
}
else // conversion ok, you can use the kwh value
{
if (kwh > 2000)
{
MessageBox.Show("Kilowatt-Hours cannot exceed 2000.");
e.Cancel = true;
}
}
You clearly mention yourself what the issue is. The input has to be something that could be converted to decimal some number.
It seems like an issue with incorrect input. Could you try using TryParse instead or you could simply change that second 'if' block to 'else if'.
decimal outputKWH;
kwh = decimal.TryParse(khtextBox.Text, out outputKWH)
I have just started programming in C#. I am trying to convert a string to int. Like this:
int.Parse(textBox1.Text);
This is working fine when I enter a value but this is giving me exception when nothing is entered and I press the button. What should I do? Is there a function to solve this? Thanks
Use int.TryParse instead, it doesn't throw exception if the parsing fails.
Converts the string representation of a number to its 32-bit signed integer equivalent. A return value indicates whether the conversion succeeded.
int number;
bool isValid = int.TryParse(textBox1.Text, out number);
if(isValid)
{
// parsing was successful
}
One way to approach this is by using int.tryParse() instead of just int.Parse(). You can then check the result to see if the input was in the correct format.
Here is a sample:
int userInput;
if(!int.TryParse(textBox1.Text, out userInput))
{
//error in input here
}
After executing, if int.TryParse() returns true, then you will have a valid value in the userInput variable.
Alternatively you can wrap it in a try-catch, but it is better to attempt the parse and handle it without exceptions if possible.
Put this following code under your button event. It will make sure that the text/numbers entered into the textbox are able to be converted into an integer. Also, it will make sure that the textbox has numbers/text entered.
if (textBox1.Text != "")
{
try
{
Convert.ToInt32(textBox1.Text);
}
catch
{
/*
Characters were entered, thus the textbox's text cannon be converted into an integer.
Also, you can include this line of code to notify the user why the text is not being converted into a integer:
MessageBox.Show("Please enter only numbers in the textbox!", "PROGRAM NAME", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
*/
}
}
/*
else
{
MessageBox.Show("Please enter numbers in the textbox!", "PROGRAM NAME", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
}
*/
This is simple. You can do this on your button click event:
int number;
if (int.TryParse(textbox1.Text, out number))
{
// number is an int converted from string in textbox1.
// your code
}
else
{
//show error output to the user
}
Try below given solution
<script type="text/javascript">
function myFunction() {
alert('Please enter textbox value.');
}
</script>
And in the button click event use below given logic.
if (TextBox1.Text == "")
{
//Call javascript function using server side code.
ClientScript.RegisterStartupScript(this.GetType(), "CallMyFunction", "myFunction()", true);
}
else
{
int value;
value = int.Parse(TextBox1.Text);
}