Develop Reference

UTF-8 escape sequence as string: surely a better way

Reviewing some old code of mine, and wondered if there was a better way to create a literal string with unicode symbols...
I have a REST interface that requires certain escaped characters; for example, a property called username with value of john%foobar+Smith that must be requested like this:
{"username":"john\u0025foobar\u002bSmith"}
My c# method to replace certain characters like % and + is pretty basic:
public static string EncodeUTF8(string unescaped) {
string utf8_ampersand = #"\u0026";
string utf8_percent = #"\u0025";
string utf8_plus = #"\u002b";
return unescaped.Replace("&", utf8_ampersand).Replace("+", utf8_plus).Replace("%", utf8_percent);
}
This seems an antiquated way to do this; surely there is some single line method using Encoding that would output literal UTF code, but I can't find any examples that aren't essentially replace statements like mine... is there a better way?

You could do it with Regex:
static readonly Regex ReplacerRegex = new Regex("[&+%]");
public static string Replace(Match match)
{
// 4-digits hex of the matched char
return #"\u" + ((int)match.Value[0]).ToString("x4");
}
public static string EncodeUTF8(string unescaped)
{
return ReplacerRegex.Replace(unescaped, Replace);
}
But i don't suggest it very much (unless you have tens of replaces). I do think it would be slower, and bigger to write.

Format placeholder in string.format to pick substring of an argument

Is there a format string for the C# string.Format method that picks a substring from the corresponding argument? Like so:
var lang1 = "EN";
var lang2 = "FR";
var shortFormat = "Foo-{0:0-0}.pdf";
var longFormat = "Foo-{0:0-1}.pdf";
string.Format(shortFormat, lang1) // Foo-E.pdf
string.Format(shortFormat, lang2) // Foo-F.pdf
string.Format(longFormat, lang1) // Foo-EN.pdf
string.Format(longFormat, lang2) // Foo-FR.pdf
To anticipate a few comments: Yes, I know the Substring method. I have also read that string.Format is slower than a simple Substring. The example above is heavily simplified. Imagine that the string.Format statement resides in one place, while the lang1/lang2 argument is an input from another place and the shortFormat/longFormat is defined in a resx file.
That is, in the place where the format is to be defined we don't know anything about the value being formatted (lang1/lang2 in the example) nor do we have any means to execute C# code. Hence we can't call any method such as Substring on the value. At the place where the formatting code runs, in turn, we take the format as a parameter, so we can't simply perform a Substring on the value because we don't know whether the format requires it or not (except if we inspect the format).

No, the string.Format does not have this feature, which is better explained here: Can maximum number of characters be defined in C# format strings like in C printf?
If you don't want to use Substring I would create an extension class for string like this: http://msdn.microsoft.com/en-us/library/bb311042.aspx
namespace CustomExtensions
{
public static class StringExtension
{
public static string ShortFormat(this string str)
{
// manipulate and return str here
}
public static string LongFormat(this string str)
{
// manipulate and return str here
}
}
}

XSLT formatting can be an option: user gets ability to provide almost everything in configuration file and even execute custom c# code in your domain if it is required.
Please also consider that changes of format can be restricted to relatively small amount of actions: crop, pad or insert one or two things in some positions. Each one can be set as individual function and provided with own parameters.

There are two ways to provide custom formatting. You can either implement IFormattable on a custom type to control how that type is always formatted, or implement IFormatProvider to override how other types are formatted in specific cases.
In your case I would suggest creating a new type to encapsulate how your software deals with language codes;
public struct LanguageCode : IFormattable {
public readonly string Code;
public LanguageCode(string code) {
Code = code;
}
public override string ToString()
=> this.ToString("L", CultureInfo.CurrentCulture);
public string ToString(string format)
=> this.ToString(format, CultureInfo.CurrentCulture);
public string ToString(string format, IFormatProvider provider){
if (String.IsNullOrEmpty(format))
format = "L";
if (provider == null)
provider = CultureInfo.CurrentCulture;
switch (format.ToUpperInvariant()){
case "L": // Long
return Code.ToString(provider);
case "S": // Short
return Code.SubString(0,1).ToString(provider);
default:
throw new FormatException($"The {format} format string is not supported.");
}
}
public static implicit operator LanguageCode(string code)
=> new LanguageCode(code);
public static implicit operator string(LanguageCode language)
=> language.Code;
}
Then from your example;
var lang1 = (LanguageCode)"EN";
LanguageCode lang2 = "FR";
var shortFormat = "Foo-{0:S}.pdf";
var longFormat = "Foo-{0:L}.pdf";

words stemmer class c#

I am trying the following stemming class :
static class StemmerSteps
{
public static string stepSufixremover(this string str, string suffex)
{
if (str.EndsWith(suffex))
{
................
}
return str;
}
public static string stepPrefixemover(this string str, string prefix)
{
if (str.StartsWith(prefix)
{
.....................
}
return str;
}
}
this class works with one prefix or suffix. is there any suggestion to allow a list of prefixes or suffixes to go through the class and compare against each (str). your kind action really appreciated.

Instead of creating your own class from scratch (unless this is homework) I would definitive use an existing library. This answer provides an example of code that that implements the Porter Stemming Algorithm:
https://stackoverflow.com/questions/7611455/how-to-perform-stemming-in-c

Put your suffix/prefixes in a collection (like a List<>), and loop through and apply each possible one. This collection would need to be passed into the method.
List<string> suffixes = ...;
for (suffix in suffixes)
if (str.EndsWith(suffix))
str = str.Remove(str.Length - suffix.Length, suffix.Length);

EDIT
Considering your comment:
"just want to look if the string starts-/endswith any of the passed strings"
may be something like this can fit your needs:
public static string stepSufixremover(this string str, IEnumerable<string> suffex)
{
string suf = suffex.Where(x=>str.EndsWith(x)).SingleOrDefault();
if(!string.IsNullOrEmpty(suf))
{
str = str.Remove(str.Length - suf.Length, suf.Length);
}
return str;
}
If you use this like:
"hello".stepone(new string[]{"lo","l"}).Dump();
it produces:
hel

The simplest code would involve regular expressions.
For example, this would identify some English suffixes:
'^(.*?)(ing|ly|ed|ious|ies|ive|es|s|ment)?$'
One problem is that stemming is not as accurate as lemmatization. Lematization would require POS tagging for accuracy. For example, you don't want to add an -ing suffix to dove if it's a noun.
Another problem is that some suffixes also require prefixes. For example, you must add en- to -rich- to add a -ment suffix in en-rich-ment -- unlike a root like -govern- where you can add the suffix without any prefix.

Easy way to check FormatString is valid?

Is there an easy way to check if a format string is valid? For example the following is code that we use to test a number format string;
public static bool IsValidFormatStringNumber(string FormatString)
{
try
{
const decimal number = 0.056m;
var formattedNumber = number.ToString(FormatString);
return formattedNumber.Length > 0;
}
catch
{
return false;
}
}
We're trying to catch an exception or determine if the resulting string has no length. This test fails however as a format string of "hsibbur" (Any rubbish) results in a string of "hsaibbur", which has length.
We want to do the same test for Percent and Date format string.

If you just want to check for standard format strings, just check that your format strings are part of that list.
If you want to check for custom format strings (that are not "Other" or "Literal strings"), you can probably craft a regex to do it.
Other than that, since format strings can be arbitrary strings, I don't think validation even applies.

If FormatString is equal to formattedNumber, that could be another case for returning false.

string.Format() Blank Zero

In my application, there are possibilities to format a string using the string.Format() function. I want to add the possibility to return blank when the result is zero.
As far as I can see, it is possible to do this using the code: 0.toString("0;; ");, but as i already mentioned, I need to use the string.Format() function (since it must be able to use for example the {0:P} format for percentage.
Does anyone knows how to blank a zero value using the string.Format() function?

String.Format() supports the ; section separator.
Try e.g. String.Format("{0:#%;;' '}", 0);.

My answer is a bit late, but you may want to try the following:
{0:#.##%;-#.##%;''}

why don't you do it with if else statement?
string result = String.Format(the value);
if(result=="0")
{
result=" ";
}

Or, perhaps more elegantly as an extension method on int:
public static class StringFormatters
{
public static string ToNonZeroString(this int i) => i == 0 ? "" : i.ToString();
}
and then
(1+1-2).ToNonZeroString()