private void buttonConvert_Click(object sender, EventArgs e)
{
//Convert number from C to F
double convertDecimal;
convertDecimal = 1.8;
textBoxF = double.Parse(textBoxC.Text) * double(convertDecimal) + 32;
^here is where I get the error
Error 1 Invalid expression term 'double'
I am pretty new to programming and but I just can't wrap my mind around trying to add, subtract, dividing, or multiplying numbers. I am trying to do a simple a simple conversion. Take the number from the Celsius textbox and convert it to Fahrenheit. I just don't understand the number part???
Thanks for your help!
double(convertDecimal) should be (double)convertDecimal
That looks like a C++ type-casting expression, which doesn't work in C#. And as convertDecimal already is of type double there's no need to cast it. Just use it directly:
textBoxF = double.Parse(textBoxC.Text) * convertDecimal + 32;
You only need to change the type of a variable (i.e. type-cast) when the variable is of a type not expected. Adding two double values is okay. Even adding a double and an int is okay because the integer is implicitly converted to a double.
Edit: You try to assign the result of the expression to a control, which will not work. You should convert the result to a string (e.g. with double.ToString), and then assign to the controls text field:
double farenheit = double.Parse(textBoxC.Text) * convertDecimal + 32;
textBoxF.Text = farenheit.ToString();
Related
This question already has answers here:
Cannot implicity convert type 'double' to 'string'
(3 answers)
Closed 4 years ago.
I am trying to make a sum in c# but i keep getting these errors.
by pressing the + button i pretty much want the numbers to be summed up in a label.
Thanks in advance.
here's my code.
private void buttonPlus_Click(object sender, EventArgs e)
{
Int32 a = 10;
double b = 20.50;
double c = 50.10;
Int32 d = 20;
labelSum.Text = (a+b+c+d);
}
Not sure why you're using Int32 and not just int.
Also, try converting the sum to a string:
labelSum.Text = (a+b+c+d).ToString();
Text property is of type String while your expression will return a numeric data type not String so, the right hand side should be returning the same type what the left hand of expression is having when assigning.
Just convert the result of sum to string by calling ToString() :
labelSum.Text = (a+b+c+d).ToString();
or like:
labelSum.Text = Convert.ToString(a+b+c+d);
public partial class Form1 : Form
{
string principal, rate, years;
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
principal = loantextBox4.Text;
rate = ratetextBox5.Text;
years = yearworktextBox2.Text;
outputlabel5.Text = principal * ((rate * (1 + rate) ^ years) / ((rate + 1) ^ years) - 1))));
What needs to be fixed I keep getting an error saying operator "*" cannot be applied to operands of type 'string' and 'string'.
You cannot apply mathematical operations on a string variable and thus you need an int or double type. I have used int. Secondly When you try to get the TextBox data in the int variable it would not be possible because TextBox.Text would return a string. Now You can convert the TextBox.Text to a int using Convert.ToInt32. If you try to put the values of the Textbox to int variable without conversion, it will give you an error stating
Cannot implicitly convert type 'string' to 'int'
and it would not even compile the program.
Whereas letz say if the user input in not a number and it we try to Convert it. For example the user input is "Mohit" and when it tries to convert the Convert.ToInt32("Mohit"); it will throw an exception. stating
An unhandled exception of type 'System.FormatException' occurred in mscorlib.dll
You can avoid getting exception or to handle the wrongly input from the user you can use Try and Catch Block
Hope this code will give you the idea
public partial class Form1 : Form
{
int principal, rate, years;
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
principal = Convert.ToInt32(loantextBox4.Text);
rate = Convert.ToInt32(ratetextBox5.Text);
years = Convert.ToInt32(yearworktextBox2.Text);
outputlabel5.Text = (principal * ((rate * (1 + rate) ^ years) / ((rate + 1) ^ years) - 1)).ToString();
You can't multiply strings. You can, however, multiply numbers. Convert your numeric strings to numbers. For example:
int years;
if (!int.TryParse(yearworktextBox2.Text, out years))
{
// string value wasn't numeric, maybe show an error?
// probably return from here as well, since the logic can't continue
}
// here the "years" value can be used for calculations
Remove the string variables you have, replace them with numeric values (int, decimal, double, etc. where appropriate) which are populated by parsing the input strings using .TryParse() (and handling errors accordingly), then you can use those values in your calculations.
Because all of your inputs are strings. You can't multiply a string.
What you need to do instead is change them to a number format. Probably just int should be fine.
This question already has answers here:
How can I convert String to Int?
(31 answers)
Closed 7 years ago.
I need to display a certain number on a label when the user input is between >=0 and <= 1. User input is a string and I need the numbers between to be a decimal or double. Obviously I can't compare the two like I did because the operators can't compare a string and decimal, double, or int.
private void voltageTextBox_TextChanged(object sender, EventArgs e)
{
var RTPower = powerTextBox.Text;
powerTextBox.CharacterCasing = CharacterCasing.Upper;
if (RTPower >= 0 && <= 1)
{
displayLabel4.Text = "1";
}
}
Error: Operator '>=' cannot be applied to operands of type 'string' and 'int'
Error: Operator '<=' cannot be applied to operands of type 'string' and 'int'
How can I make that if statement work? Do I have to keep it as a string, display it in label, convert the label to an integer then re-display it? I know I can make that work, but that is far too complicated. I just need an easier way to do this.
int RTPower = Int32.Parse(powerTextBox.Text);
or for decimal values
decimal RTPower = Decimal.Parse(powerTextBox.Text);
You need to convert the value from a string to an int.
Also, I assume you are new to c# - my advice would be to avoid using var and explicitly declare your variables. It will make things clear and easier for you to learn and understand.
You can convert to int like
int x = Int32.Parse(RTPower);
then you can compare x.
If, however, you know that the user input will be between [0, 9] then you could use
if(RTPower >= "0" && <= "1")
because strings are compared lexicographically so "1" is under "9" but "10" is under "2".
The first way is much better though, because it works for all numerical user inputs
I need a simple random number for a loop that I am creating, and I can't for the life of me figure out what I am doing wrong here. Can someone look at the code below and explain to me why it's giving me the following errors:
Error 1 The best overloaded method match for 'System.Random.Next(int,
int)' has some invalid arguments
Error 2 Argument 1: cannot convert
from 'decimal' to 'int'
Error 3 Argument 2: cannot convert from
'decimal' to 'int'
I am trying to pull minimum and maximum values for the range from Numeric Up/Down controls. I would assume that LINQ or C# would have a simple, one line generator, but I can't find it.
Random rnd1 = new Random();
var integer = rnd1.Next(numericUpDown_RandomMin.Value,
numericUpDown_RandomMax.Value);
textbox.Text = integer.ToString();
NumericUpDown.Value returns a decimal, while Next() accepts an integer. You probably want to cast it to an integer first:
var integer = rnd1.Next((int)numericUpDown_RandomMin.Value, (int)numericUpDown_RandomMax.Value);
Well, first of all numericUpDown_RandomMin.Value and ..._RandomMax.Value are not int, so you might need to cast:
var integer = rnd1.Next((int)numericUpDown_RandomMin.Value, (int)numericUpDown_RandomMax.Value);
Other than that, what errors are you getting?
NumericUpDown is a decimal, you need to convert to an int.
var integer = rnd1.Next((int)numericUpDown_RandomMin.Value, (int)numericUpDown_RandomMax.Value);
Random.Next expects two Int32 values, but NumericUpDown.Value property is a decimal. Because conversion from decimal to int looses some value precision you have to do it explicitly :
rnd1.Next((int)numericUpDown_RandomMin.Value, (int)numericUpDown_RandomMax.Value);
Since NumericUpDown.Value's return type is Decimal, you need to explicitly convert your numericUpDown_RandomMin.Value and numericUpDown_RandomMax.Value values to Int32 because Random.Next(Int32, Int32) takes two parameter as Int32. Like;
Random rnd1 = new Random();
var integer = rnd1.Next((int)numericUpDown_RandomMin.Value, (int)numericUpDown_RandomMax.Value);
textbox.Text = integer.ToString();
I have the following code:
int a = 50;
float b = 50.60f;
a = int.Parse(b.ToString());
On run time this parsing gives as error. Why it is please guide me.
Thanks
It's trying to parse the string "50.6" - that can't be parsed as an integer, because 50.6 isn't an integer. From the documentation:
The s parameter contains a number of the form:
[ws][sign]digits[ws]
Perhaps you want to parse it back as a float and then cast to an integer?
a = (int) float.Parse(b.ToString());
This is because int.Parse throws NumberFormatException if the string does not contain a parsable integer; 50.6 is not a prasable integer.
You are trying to parse a string that does not represent an integer into an integer.
This is why you are getting an exception.
It gives an error because you are trying to parse as int a string representing a float.
float b = 50.60f; // b = 50.6
// b.ToString() = "50.6" or "50,6" depending on locale
// int.Parse("50.6") MUST give an error because "50.6" is
// not a string representation of an integer
What is it that you want to do? Convert a float to an int? Just do this:
float b = 50.6f;
int a = (int)b;
That will truncate the value of b to simply 50.
Or do you want it rounded off to the nearest integer?
int a = (int)Math.Round(b);
Is the error message not specific enough?
Input string was not in a correct format.
int.Parse must take a string which can be parsed to an integer. The string "50.6" does not fulfil that requirement!