I am trying to convert a decimal to an integer safely.
Something like
public static bool Decimal.TryConvertToInt32(decimal val, out int val)
this will return false if it cannot convert to an integer, and true w/ successful output if it can.
This is to avoid catching the OverflowException in decimal.ToInt32 method. What is the easiest way to do this?
Here:
public static bool TryConvertToInt32(decimal val, out int intval)
{
if (val > int.MaxValue || val < int.MinValue)
{
intval = 0; // assignment required for out parameter
return false;
}
intval = Decimal.ToInt32(val);
return true;
}
I would write an extension method for class decimal like this:
public static class Extensions
{
public static bool TryConvertToInt32(this decimal decimalValue, out int intValue)
{
intValue = 0;
if ((decimalValue >= int.MinValue) && (decimalValue <= int.MaxValue))
{
intValue = Convert.ToInt32(decimalValue);
return true;
}
return false;
}
}
You can use it in that way:
if (decimalNumber.TryConvertToInt32(out intValue))
{
Debug.WriteLine(intValue.ToString());
}
Compare the decimal against int.MinValue and int.MaxValue prior to the conversion.
What's wrong with using Int32.TryParse(string) ?
Why are you trying to avoid catching the OverflowException? It is there for a reason and you should totally catch it where you call Decimal.ToInt32(). Exceptions are used widely throughout the framework and users should catch them. The Try methods can help you around them to make code tighter and cleaner, but where the framework doesn't have a suitable method (Decimal.TryConvertToInt32() in this case) catching OverflowException is the appropriate thing to do. It is actually more clear than making an extension class or writing your own separate static method (both of those involve writing your own code where the framework is already giving you this functionality).
Related
In C# Convert.ToInt32() and any method of Convert class can handle null values but all these method not handling "" as input. Throws an error "input string not in correct format"
Is there any way to handle/Convert "" to its specific value? like
Convert.ToInt32("") convert to 0
Convert.ToDecimal("") convert to 0.0
with out using if conditions
Thanks.
The POD classes in C# have a method just for this reason:
Int32.TryParse
You could even write an extension method to make this easier for you:
public static class Extensions {
public static decimal MyDecimalParse(this string val) {
decimal ret = decimal.Zero;
decimal.TryParse(val, out ret);
return ret;
}
} // eo class extension
Try int.TryParse
int i;
bool b = int.TryParse("", out i);
Console.WriteLine(b);
There isn't anything inherent in the frameworks that do this for you. It probably doesn't make sense for the entire community to understand "" as defaulting to 0 or 0.0 as you would want. I would recommend writing your own method that does what you specifically want.
Something to the effect of:
public class MyConvert
{
public static int ToInt32(string input)
{
return String.IsNullOrEmpty(input) ? 0 : Convert.ToInt32(input);
}
}
I realize you don't want to do the if check but you will have to check it one way or another (either by checking .IsNullOrEmpty or .TryParse), so abstracting it into your own convert method at least means you don't have to do it every time.
When using Code Contracts I get the warning:
Detected call to method
'System.Int32.TryParse(System.String,System.Int32#)' without [Pure] in
contracts of method
Having a class with interface and code contracts defined on the inteface like the code below. The question is how to check that the string orgNumberWithoutControlDigit can be converted to an valid integer, as it's a prereq for the modulus to work?
public string getControlDigit(string orgNumberWithoutControlDigit)
{
List<int> orgNumberNumbers = this.getNumberList(orgNumberWithoutControlDigit);
List<int> productList = orgNumberNumbers.Zip(this.weightNumberList, (first, second) => first * second).ToList();
int modular = productList.Sum() % 11;
string controlDigit = getControlDigit(modular);
return controlDigit;
}
private static string getControlDigit(int modular)
{
string controlDigit;
if (modular == 0)
{
controlDigit = "0";
}
else if (modular == 1)
{
controlDigit = "-";
}
else
{
int result = 11 - modular;
controlDigit = result.ToString();
}
return controlDigit;
}
[ContractClass(typeof(CalculateOrgNumberControlDigitBusinessContract))]
public interface ICalculateOrgNumberControlDigitBusiness
{
string getControlDigit(string orgNumberWithoutControlDigit);
}
[ContractClassFor(typeof(ICalculateOrgNumberControlDigitBusiness))]
public abstract class CalculateOrgNumberControlDigitBusinessContract:ICalculateOrgNumberControlDigitBusiness
{
public string getControlDigit(string orgNumberWithoutControlDigit)
{
Contract.Requires(orgNumberWithoutControlDigit.Length == 8);
int parseResult;
Contract.Requires(int.TryParse(orgNumberWithoutControlDigit, out parseResult));
Contract.Ensures(parseResult >= 0);
var result = Contract.Result<string>();
Contract.Ensures(result != null && result.Length == 1);
return default(string);
}
}
I understand what you want to achieve, but I would say that passing orgNumberWithoutControlDigit as a string to getControlDigit [sic] is the real culprit here.
Even if you could make your contract to work - the caller must also convert the string to int in order to satisfy your contract. Now if the caller already have made that conversion to an int, why not let it pass that int instead?
I am a huge fan of Code Contracts and use it in most of my projects, and I have learned that it is not a silver bullet. So if you have to have a string parameter, remove the contract altogether and simply make sure your string is in a valid format before use.
Maybe an OrgNumberValidator helper would be a better choice than relying on contracts for this?
EDIT: Actually, I would recommend creating an OrgNumber class for handling them.
You can create a pure helper method instead of calling int.TryParse directly:
[Pure]
private static bool IsInt(string s)
{
int n;
return int.TryParse(s, out n);
}
You could go further and wrap the TryParse in a try block, returning false if any type of exception is thrown (just to be on the safe side).
However, I tend to share Michael's opinion that you would do better by avoiding passing strings about to represent integers if you can.
I need to limit the value on overflow.
I implemented this as follows:
public static sbyte LimitValueToSByte(this int val)
{
if (val > sbyte.MaxValue) return sbyte.MaxValue;
if (val < sbyte.MinValue) return sbyte.MinValue;
return (sbyte)val;
}
Is there a more elegant way?
This is the code in a time critical system, therefore performance is important.
That seems like a perfectly readable and valid code that doesn't need any improvement whatsoever. It's just the name of the method. Maybe use ToSbyte rather than LimitValueToSByte.
Can't think of a better way to write that function.
I'd call it ClampToSByte, since this kind of limiting operation is usually called Clamp. Limit is a bit less specific, and allows for other boundary conditions, such as wrapping around.
You should be careful if you implement similar code for floating point numbers. In particular you need to decide what behavior you want for NaNs and signed zeros. But luckily that are no issues with integral values.
Looks pretty good to me. If you want something more elegant, how about a generic clamp function?
public static T Clamp<T>(this T value, T min, T max)
where T : IComparable<T>
{
if (value.CompareTo(min) <= 0) return min;
if (value.CompareTo(max) >= 0) return max;
return value;
}
(Warning: I didn't test this.) You could use it like this:
int a = 42;
sbyte b = (sbyte)a.Clamp(sbyte.MinValue, sbyte.MaxValue);
My new solution of this problem:
public static sbyte Clamp(this int val)
{
return (sbyte)Math.Max(Math.Min(value, sbyte.MaxValue), sbyte.MinValue);
}
intID1 = Int32.Parse(myValue.ToString());
intID2 = Convert.ToInt32(myValue);
Which one is better and why?
They are exactly the same, except that Convert.ToInt32(null) returns 0.
Convert.ToInt32 is defined as follows:
public static int ToInt32(String value) {
if (value == null)
return 0;
return Int32.Parse(value, CultureInfo.CurrentCulture);
}
Well, Reflector says...
public static int ToInt32(string value)
{
if (value == null)
{
return 0;
}
return int.Parse(value, CultureInfo.CurrentCulture);
}
public static int Parse(string s)
{
return Number.ParseInt32(s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo);
}
So they're basically the same except that Convert.ToInt32() does an added null check.
It depends on what you mean by "better" because "better" is subjective.
For instance - code readability. Some people prefer to see "Convert" in their code; others prefer to see "Parse".
In terms of speed, they're also both roughly equal according to these benchmarks.
Or do you always wants a value returned? As others have mentioned, ConvertTo returns a 0 (zero) for null values whereas you don't get that option with Parse.
One thing that has bothered me about C# since its release was the lack of a generic IsNumeric function. I know it is difficult to generate a one-stop solution to detrmine if a value is numeric.
I have used the following solution in the past, but it is not the best practice because I am generating an exception to determine if the value is IsNumeric:
public bool IsNumeric(string input)
{
try
{
int.Parse(input);
return true;
}
catch
{
return false;
}
}
Is this still the best way to approach this problem or is there a more efficient way to determine if a value is numeric in C#?
Try this:
int temp;
return int.TryParse(input, out temp);
Of course, the behavior will be different from Visual Basic IsNumeric. If you want that behavior, you can add a reference to "Microsoft.VisualBasic" assembly and call the Microsoft.VisualBasic.Information.IsNumeric function directly.
You can use extension methods to extend the String type to include IsInteger:
namespace ExtensionMethods
{
public static class MyExtensions
{
public static bool IsInteger(this String input)
{
int temp;
return int.TryParse(input, out temp);
}
}
}
Rather than using int.Parse, you can use int.TryParse and avoid the exception.
Something like this
public static bool IsNumeric(string input)
{
int dummy;
return int.TryParse(input, out dummy);
}
More generically you might want to look at double.TryParse.
One thing you should also consider is the potential of handling numeric string for different cultures. For example Greek (el-GR) uses , as a decimal separator while the UK (en-GB) uses a .. So the string "1,000" will either be 1000 or 1 depending on the current culture. Given this, you might consider providing overloads for IsNumeric that support passing the intended culture, number format etc. Take a look at the 2 overloads for double.TryParse.
I've used the following extension method before, if it helps at all:
public static int? AsNumeric(this string source)
{
int result;
return Int32.TryParse(source, out result) ? result : (int?)null;
}
Then you can use .HasValue for the bool you have now, or .Value for the value, but convert just once...just throwing it out there, not sure what situation you're using it for afterwards.
If you use Int32.TryParse then you don't need to wrap the call in a TryCatch block, but otherwise, yes that is the approach to take.
Not exactly crazy about this approach, but you can just call the vb.net isNumeric function from C# by adding a reference to the Microsoft.VisualBasic.dll library...
bool x= Microsoft.VisualBasic.Information.IsNumeric("123");
The other approaches given are superior, but wanted to add this for the sake of completeness.
Lot's of TryParse answers. Here's something a bit different using Char.IsNumber():
public bool IsNumeric(string s)
{
for (int i = 0; i < s.Length; i++)
{
if (char.IsNumber(s, i) == false)
{
return false;
}
}
return true;
}
Take a look on the following answer:
What is the C# equivalent of NaN or IsNumeric?
Double.TryParse takes care of all numeric values and not only ints.
Another option - LINQ!
public static class StringExtensions
{
public static bool IsDigits(this String text)
{
return !text.Any(c => !char.IsDigit(c));
}
}
Note that this assumes you only want digits 0-9. If you want to accept decimal point, sign, exponent, etc, then repalce IsDigit() with IsNumber().
I've been using the following small code snippet for years as a pure C# IsNumeric function.
Granted, it's not exactly the same as the Microsoft.VisualBasic library's IsNumeric function as that (if you look at the decompiled code) involves lots of type checking and usage of the IConvertible interface, however this small function has worked well for me.
Note also that this function uses double.TryParse rather than int.TryParse to allow both integer numbers (including long's) as well as floating point numbers to be parsed. Also note that this function specifically asserts an InvariantCulture when parsing (for example) floating point numbers, so will correctly identify both 123.00 and 123,00 (note the comma and decimal point separators) as floating point numbers.
using System;
using System.Globalization;
namespace MyNumberFunctions
{
public static class NumberFunctions
{
public static bool IsNumeric(this object expression)
{
if (expression == null)
{
return false;
}
double number;
return Double.TryParse(Convert.ToString(expression, CultureInfo.InvariantCulture), NumberStyles.Any, NumberFormatInfo.InvariantInfo, out number);
}
}
}
Usage is incredibly simple, since this is implemented as an extension method:
string myNumberToParse = "123.00";
bool isThisNumeric = myNumberToParse.IsNumeric();
public bool IsNumeric(string input)
{
int result;
return Int32.TryParse(input,out result);
}
try this:
public static bool IsNumeric(object o)
{
const NumberStyles sty = NumberStyles.Any;
double d;
return (o != null && Double.TryParse(o.ToString(), sty, null, out d));
}
You can still use the Visual Basic function in C#. The only thing you have to do is just follow my instructions shown below:
Add the reference to the Visual Basic Library by right clicking on your project and selecting "Add Reference":
Then import it in your class as shown below:
using Microsoft.VisualBasic;
Next use it wherever you want as shown below:
if (!Information.IsNumeric(softwareVersion))
{
throw new DataException(string.Format("[{0}] is an invalid App Version! Only numeric values are supported at this time.", softwareVersion));
}
Hope, this helps and good luck!