Develop Reference

How do i get the total average?

private void txtFinal_Leave_1(object sender, EventArgs e)
{
int prelim;
int midterm;
int final;
decimal average;
string remarks;
prelim = int.Parse(txtPrelim.Text);
midterm = int.Parse(txtMidterm.Text);
final = int.Parse(txtFinal.Text);
average = (prelim + midterm + final) / 3;
txtAverage.Text = average.ToString();
if (average >= 75)
{
remarks = "passed";
}
else
{
remarks = "failed";
}
txtRemarks.Text = remarks;
// this is the output 83 passed
// I want to be like this 83.25 passed
}

average = (prelim + midterm + final) / 3.0m;
This will fix your problem.
Int is an integer type; dividing two ints performs an integer division, i.e. the fractional part is truncated since it can't be stored in the result type (also int!). Decimal, by contrast, has got a fractional part. By invoking Decimal.Divide, your int arguments get implicitly converted to Decimals.
You can enforce non-integer division on int arguments by explicitly casting at least one of the arguments to a floating-point type, e.g.: 3.0m this is casting to decimal !

please upgrade your code as follow:
average = Convert.ToDecimal(prelim + midterm + final) / 3;
txtAverage.Text = string.Format("{0:0.00}", average);

Input String was not in a correct form

There are two text boxes called unitprice.txt and quantity.txt. there is another textbox called total.txt which keeps on getting updated as the when ever the user input unit price and quantity.
Oonce the user input these two those two textboxes are getting empty and total.txt getting updated by the total. it needs to be done continuously but in my code it is not and saying
INPUT STRING WASN'T IN A CORRECT FORM.
int tot = 0;
int sum = 0;
tot = int.Parse(unitprice.Text) * int.Parse(quantitytxt.Text);
sum = int.Parse(total.Text) + tot;
total.Text = sum.ToString();
once the user enters the unit price and quantity total text boxe is updated by the toal. and again user enters the second item's unit price and quantity then previous value in total text box needs to be updated which means that new total generated from the second item needs to be added to previous total.(2500+3000=5500)
Hey it was solved but in this way.
int sum = 0;
private void button2_Click(object sender, EventArgs e)
{
try
{
sum += int.Parse(qtytxt.Text) * int.Parse(unitprice.Text);
total.Text = sum.ToString();
}
catch (Exception er)
{
MessageBox.Show(er.Message);
}

First of all check if text box value is not coming empty or not,If it is coming empty then set 0 as default while converting to parse Int otherwise it will show exception. see below code it will help you.
int tot = 0;
int sum = 0;
tot = int.Parse(string.IsNullOrEmpty(unitprice.Text.Trim()) ? "0" : unitprice.Text.Trim()) * int.Parse(string.IsNullOrEmpty(quantitytxt.Text.Trim()) ? "0" : quantitytxt.Text.Trim());
sum = int.Parse(string.IsNullOrEmpty(total.Text.Trim()) ? "0" : total.Text.Trim()) + tot;
total.Text = sum.ToString();

You are trying to parse a string value that is textbox value to integer, so you shouldn't do like the above, because may be it contains empty string or null value too. So, follow the below method of conversion, so that errors may not occur.
tot = Convert.ToInt32(Convert.ToString(unitprice.Text)) * Convert.ToInt32(Convert.ToString(quantitytxt.Text));
Why you should follow the above method is, the Convert.ToString() will handle the null values and convert the null values to an Empty string and the Convert.ToInt32() will convert an empty string to 0 value.

If you want another option, you can try Int32.TryParse(a_string_here, an_out_int_here);
For more, look at the documentation here:MSDN TryParse
It'll take a string and try to parse it to a valid int... if it fails, it returns 0.
int a ;
Int32.TryParse("5",out a);
System.Out.WriteLine("a="+a); // Will be: a=5
Int32.TryParse("e",out a);
System.Out.WriteLine("a="+a); // Will be: a=0

First of all check if text box value is not coming empty, as if you will parse it into Int and when its empty, there will be this or similar exception.
int tot = 0;
int sum = 0;
tot = int.Parse(unitprice.Text!=String.Empty?unitprice.Text:"0") * int.Parse(quantitytxt.Text!=String.Empty?quantitytxt.Text:"0");
sum = int.Parse(total.Text!=String.Empty?total.Text:"0") + tot;
total.Text = sum.ToString();
You can also try:
int tot = 0;
int sum = 0;
tot = Convert.ToInt32(unitprice.Text!=String.Empty?unitprice.Text:"0") * Convert.ToInt32(quantitytxt.Text!=String.Empty?quantitytxt.Text:"0");
sum = Convert.ToInt32(total.Text!=String.Empty?total.Text:"0") + tot;
total.Text = sum.ToString();

Try this:
int tot = 0;
int sum = 0;
tot = Convert.ToInt32(unitprice.Text.Replace(" ", "")) * Convert.ToInt32(quantitytxt.Text.Replace(" ", ""));
sum = Convert.ToInt32(total.Text.Replace(" ", "")) + tot;
total.Text = sum.ToString();
If this throws an exception your textboxes probably has unwanted characters (i.e. commas: "1,000.00" or letters) or empty that makes the convertion throw an exception.

the problem is...if the string is other than numbers ............
Any string value other than numbers will show an error saying INPUT STRING WASN'T IN A CORRECT FORM!!!.
there is a solution for this.....insert your code inside try catch block
try{ your code here}catch(FormatException){}
or find another mechanism to avoid strings other than numbers....

Int32.Parse() will throw an exception if the input value is not an integer. Use Int32.TryParse() to convert a value without throwing an exception. If the conversion fails, TryParse() will return false and zero will be returned:
int intValue = -1;
bool result;
result = Int32.TryParse("23", out intValue); // result = true, intValue = 23
result = Int32.TryParse("AB", out intValue); // result = false, intValue = 0
EDIT: For your specific case, try this:
int tot = 0;
int sum = 0;
int price = 0; // output parameter to receive value
int quantity = 0; // output parameter to receive value
int total = 0; // output parameter to receive value
TryParse(unitprice.Text, out price); // price contains the unit price value
TryParse(quantitytxt.Text out quantity); // quantity contains the quantity value
TryParse(total.Text, out total); // total contains the total value
tot = price * quantity;
sum = total + tot;
total.Text = sum.ToString();

int tot = 0;
int sum = 0;
tot = int.Parse(unitprice.Text+"0") * int.Parse(quantitytxt.Text+"0");
sum = int.Parse(total.Text+"0") + tot;
total.Text = sum.ToString();
Try this code.

Converting between negative Hexadecimal and negative Decimal gives wrong results

I am attempting to manually convert numbers between decimal and hexadecimal. I have it working for positive numbers and converting a negative decimal to 'negative' hexadecimal but I can't convert it from 'negative' hexadecimal to negative decimal.
Here is the code I am attempting to work with:
private string HexToDecimal(char[] toConvert)
{
if (negativeValue)
{
negativeValue = false;
long var = Convert.ToInt64(HexToDecimal(ResultLabel.Text.ToCharArray()));
long valueToHex = var - (long)Math.Pow(16, 15);
return ResultLabel.Text = valueToHex.ToString();
}
else
{
double total = 0;
//Convert hex to decimal
HexOrDecimalLabel.Text = "Decimal";
//TODO: create int array from indivial int
char[] charArray = toConvert;
long[] numberArray = HexSwitchFunction(charArray);
//TODO: reverse array
Array.Reverse(numberArray);
//loop array, times value by 16^i++, adding to total. This is the method used to convert hex to decimal
double power = 0;
foreach (int i in numberArray)
{
total += (i * (Math.Pow(16, power)));
power++;
}
//set the result label to total
isHex = false;
AllowHexButtons();
return ResultLabel.Text = total.ToString();
}
}
For instance, I can turn - 10 into FFFFFFFFFFFFFFF6, but when i attempt to turn that into decimal, I get 1.15292150460685E+18, which I can't do any equations with.
Does anyone know of a way around this?

This is because double uses a different representation for negative numbers. Changing the type of total and power from double to long will fix the problem.

How can I display decimal position based on my decimal position value?

decimal value = 10;
int decimalPosition= 3; //this decimalPosition will be dynamically change.
decimal formatted = Math.Round(value, decimalPosition);
if decimalPosition =3;
I need to display formatted value like : 10.000.
if decimalPosition =5;
I need to display formatted value like : 10.00000.
Note: I must use Round function.

decimal value has no format assigned - it is just a numeric value. You can specify the format it's being printed out with, but you have to do it while printing or when the string is being created:
decimal value = 10;
int decimalPosition = 3; //this decimalPosition will be dynamically change.
decimal formatted = Math.Round(value, decimalPosition);
string format = string.Format("{{0:0.{0}}}", string.Concat(Enumerable.Repeat("0", decimalPosition).ToArray()));
string formattedString = string.Format(format, formatted);
Console.WriteLine(formattedString);
Prints 10.000 into console.
Another way of specifying format like that:
var format = string.Format("{{0:f{0}}}", decimalPosition);

You can try something like this:-
decimal.Round(yourValue, decimalPosition, MidpointRounding.AwayFromZero);

u can try it:--
decimal value = 10;
int decimalPosition = 3; //this decimalPosition will be dynamically change.
string position = "";
for (int i = 0; i < decimalPosition; i++)
{
position += "0";
}
string newValue = value.ToString() + "." + position;
decimal formatted = Convert.ToDecimal(newValue);

Use FORMATASNUMBER(Value, decimalPosition) instead of math.round
Sorry, I forgot it was c# not VB
But you can read about it here on MSDN
http://msdn.microsoft.com/en-us/library/microsoft.visualbasic.strings.formatnumber(v=VS.80).aspx
The command is String.FormatNumber(blah blah blah)
and the ACTUAL declaration is...
public static string FormatNumber (
Object Expression,
[OptionalAttribute] int NumDigitsAfterDecimal,
[OptionalAttribute] TriState IncludeLeadingDigit,
[OptionalAttribute] TriState UseParensForNegativeNumbers,
[OptionalAttribute] TriState GroupDigits
)

Convert string to double with 2 digit after decimal separator

All began with these simple lines of code:
string s = "16.9";
double d = Convert.ToDouble(s);
d*=100;
The result should be 1690.0, but it's not. d is equal to 1689.9999999999998.
All I want to do is to round a double to value with 2 digit after decimal separator.
Here is my function.
private double RoundFloat(double Value)
{
float sign = (Value < 0) ? -0.01f : 0.01f;
if (Math.Abs(Value) < 0.00001) Value = 0;
string SVal = Value.ToString();
string DecimalSeparator = System.Globalization.CultureInfo.CurrentCulture.NumberFormat.CurrencyDecimalSeparator;
int i = SVal.IndexOf(DecimalSeparator);
if (i > 0)
{
int SRnd;
try
{
// вземи втората цифра след десетичния разделител
SRnd = Convert.ToInt32(SVal.Substring(i + 3, 1));
}
catch
{
SRnd = 0;
}
if (SVal.Length > i + 3)
SVal = SVal.Substring(0, i + 3);
//SVal += "00001";
try
{
double result = (SRnd >= 5) ? Convert.ToDouble(SVal) + sign : Convert.ToDouble(SVal);
//result = Math.Round(result, 2);
return result;
}
catch
{
return 0;
}
}
else
{
return Value;
}
But again the same problem, converting from string to double is not working as I want.
A workaround to this problem is to concatenate "00001" to the string and then use the Math.Round function (commented in the example above).
This double value multiplied to 100 (as integer) is send to a device (cash register) and this values must be correct.
I am using VS2005 + .NET CF 2.0
Is there another more "elegant" solution, I am not happy with this one.

Doubles can't exactly represent 16.9. I suggest you convert it to decimal instead:
string s = "16.9";
decimal m = Decimal.Parse(s) * 100;
double d = (double)m;
You might just want to keep using the decimal instead of the double, since you say you'll be using it for monetary purposes. Remember that decimal is intended to exactly represent decimal numbers that fit in its precision, while double will only exactly represent binary numbers that do.

Math.Round(number, 1)
Edit I got the wrong question - the rounding problems are inherent to a floating point type (float, double). You should use decimal for this.

The best solution for not going be crazy is:
string s = "16.9";
For ,/.
double d = Convert.ToDouble(s.Replace(',','.'),System.Globalization.CultureInfo.InvariantCulture);
For rounding:
Convert.ToDouble((d).ToString("F2"));