I need to make a possibility to open a webpage either with an additional parameter or without one. If it has a parameter, I'll add it with the string.format function. Sometimes I need to format this parameter before opening the url, however, I don't want to make the code too specific.
The Parameter is always a string and I would need to cut the end of this string. Is it possible to do something in the string to be formatted to cut the unneeded text? If so how would the {0} have to look that it works?
string url = "http://foo.bar/xt:{0}";
string parameter = "abcdefghi";
if (Regex.Matches(Regex.Replace(url,
#"(\{{2}|\}{2})", ""), // removes escaped curly brackets
#"\{(\d+)(?:\:?[^}]*)\}")
.OfType<Match>().Any())
{
Process.Start(string.Format(url, parameter));
}
else
{
Process.Start(url);
}
Instead of abcdefghi I would like to have as parameter just abcdefg for instance. But this should be configurable via url. Something like {0:7) or so...
You have to write this kind of logic yourself. What you can do, however, is wrap this in an extension method so you don't have to duplicate it everywhere:
public static class StringExt
{
public static string Truncate(this string value, int maxLength)
{
if (string.IsNullOrEmpty(value)) return value;
return value.Length <= maxLength ? value : value.Substring(0, maxLength);
}
}
Now we can write:
var someString = "...";
someString = someString.Truncate(2);
Related
I'm beginer in C#. Now I have next task: In method I get template and arguments and I have to return formated string.
For example:
template = "Hello, {name}!"
name = "Bob"
So result must be a string -> Hello, Bob!
public static string GetHelloGreeting(string template, string name)
{
return string.Format(template, name);
}
String.Format expects an index in the braces. You want to pass the name in it, so you can replace it with the actual name value.
I'd suggest to use String.Replace:
public static string GetHelloGreeting(string template, string name)
{
return template.Replace("{name}", name);
}
You could provide a method which is more reusable. For example:
public static string ReplaceAll(string template, params (string key, string value)[] replacements)
{
foreach (var kv in replacements)
{
template = template.Replace("{"+ kv.key + "}", kv.value);
}
return template;
}
Your example:
string res = ReplaceAll("Hello, {name}!", ("name", "Bob"));
but also possible with multiple parameters:
string res = ReplaceAll("Hello, {name}! Now it's {time}", ("name", "Bob"), ("time", DateTime.Now.ToString("HH:mm")));
The value of your template parameter will have to change somehow. If you want to use string interpolation, this answer shows that. So
template = $"Hello, {name}"; in which case you wouldn't need to use String.Format at all. Just make sure you define name before you define template.
Or you could use String.Format(template, name); like you have but you would need template = "Hello, {0}!";
The 0 is the index of the variable that will go in that position. For more info see String.Format
when specifying a format you use an index for the parameters that will follow. It is called a composite format string:
string template = "Hello, {0}!"
this makes it independent of variable names. But the true reason is that the overload of the Format method that you are using takes a params array as parameter as you can see in the method signature:
public static string Format (string format, params object?[] args);
so the index that is found in the template will be applied to extract the objects on the appropriate places from the array of objects that you pass into the method
If you want to use string.Format(), the template must be correct. Add the character $ at the beginning of the template:
try this:
string name = "Bob";
string template = $"Hello, {name}!";
Console.WriteLine(GetHelloGreeting(template, name)); // Hello, Bob!
public static string GetHelloGreeting(string template, string name)
{
return string.Format(template, name);
}
reult:
Hello, Bob!
I'm newbie to c#, So i tried the below program, which will change the case of the first character of the string
public class StringBuilder
{
public static string ChangeFirstLetterCase(string inputdata)
{
if(inputdata.Length > 0)
{
char[] charArray = inputdata.ToCharArray();
charArray[0] = char.IsUpper(charArray[0]) ?
char.ToLower(charArray[0]) : char.ToUpper(charArray[0]);
//return new string(charArray);
return charArray.ToString();
}
return inputdata;
}
}
class Program
{
static void Main(string[] args)
{
var a = StringBuilder.ChangeFirstLetterCase("vishnu");
Console.WriteLine(a);
Console.ReadLine();
}
}
Since the return type of this method ChangeFirstLetterCase() is a string. So I'm just doing the conversion like below
`return charArray.ToString();`
So in the method call it is returning the System.Char[]
Alternatively I tried the below one as well
`return new string(charArray);`
So this is returning the value as expected
Argument to the method - "vishnu"
Return value - "Vishnu"
So my question here is
Since the return type of the method is string, what's wrong with below conversion?
return charArray.ToString();
How do we know when to return as new string?.
return new string(charArray);
Please provide me some example
If you return the char array as a String, it will return you the name of the object System.Char[]. This is because the ToString method of char arrays does not build the characters of the array into a usable string, but simply makes a String that states the type of object.
However, if you use new String(char[]), this will read the contents of the char array to build a string out of whatever characters are in the char array. So, you will want to use new String(char[]) for most of your String building, I cannot think of any real uses for using the ToString() on a char array.
So, for your example, you should use return new String(charArray); instead of return charArray.ToString();.
charArray.ToString(); returns the type name because it's implemented that way, for getting string back from a character array you will always have to use String class constructor.
ToString method for char[] is not implemented in a way to return the character array back as a string literal, so use String constructor as you did in the second case.
You could return:
if(inputData[0].IsLower())
return string.Concat(inputData[0].ToUpper(), inputData.Substring(1));
else
return string.Concat(inputData[0].ToLower(), inputData.Substring(1));
Your value would already be a usable string and wouldn't need to have a char[].
I'm not really sure what you gain from converting the string to a char array to being with.
I have to manage a particular string formatting/padding condition. To be short I need to pad a string argument only if the argument length is 0. If I use the typical aligment parameter the padding is made if the length of the argument is smaller then the provided alignment value. For example:
string format = "#{0,10}#";
string argument;
string output;
argument = Console.ReadLine();
output = String.Format(format, argument);
String.WriteLine(output);
If I enter "try" as a value I got this result:
#try #
If I enter "trytrytrytry" I got:
#trytrytrytry#
What I would like to happen is depicted below:
Entering "" I would like to have:
# #
but entering "try" I would like to have:
#try#
The code I'm going to write should be as much generic as possibile since the format parameter is not static and is defined at runtime.
The best practice to do this is to define a custom string formatter. Unluckly it seems that the customization code can only act on the 'format' portion of the format parameter of the String.Format() method.
Indeed If I define a custom formatter:
public class EmptyFormatter : IFormatProvider, ICustomFormatter
{
public object GetFormat(Type formatType)
{
if (formatType == typeof(ICustomFormatter))
return this;
else
return null;
}
public string Format(string format, object arg, IFormatProvider formatProvider)
{
if (!this.Equals(formatProvider))
return null;
if (string.IsNullOrEmpty(format))
throw new ArgumentNullException();
return numericString;
}
}
The format and arg parameters of the Format method didn't contain the alignment parameter then I cannot actually check what lenght of the padding value should be applied and therefore I cannot act properly. Moreover this part of the 'formatting' of the string seems to be applied somewhere else but I have not idea where.
Is there a way to 'alter' this behaviour ?
A format item has the following syntax:
index[,alignment][ :formatString] }
The reason the format parameter is null is because there is no formatString component, there is only alignment. I couldn't find a way to access the alignment component from the Format method. However, one (ugly) solution is to set the formatString to be the same as the alignment, so that you can access it using the format parameter:
#{0,10:10}#
A less ugly solution would be to create your own method extension that first extracts the alignment from the given format and then calls the traditional String.Format method.
For example:
public static string StringFormat(this string Arg, string Format) {
//extract alignment from string
Regex reg = new Regex(#"{[-+]?\d+\,[-+]?(\d+)(?::[-+]?\d+)?}");
Match m = reg.Match(Format);
if (m != null) { //check if alignment exists
int allignment = int.Parse(m.Groups[1].Value); //get alignment
Arg = Arg.PadLeft(allignment); //pad left, you can make the length check here
Format = Format.Remove(m.Groups[1].Index - 1, m.Groups[1].Length + 1); //remove alignment from format
}
return (string.Format(Format, Arg));
}
To use the code:
string format = "#{0,10}#";
string argument = "try";
string output = argument.StringFormat(format); //"# try#"
How do I go about displaying a format string as-is?
I have a property decorated with some data annotations:
[DisplayFormat(DataFormatString = "{0:MM/dd/yyyy}")]
public blah blah { get; set; }
I now have a reference to the format string:
string format = metadata.DisplayFormatString; // == {0:MM/dd/yyyy}
I want to display this format string to the user without manually typing it in my view. Is there a nice way (not replace chars with empty string) to get MM/dd/yyyy from the string format?
I thing using replace is a nice way too. If you're concerned about clutter in the view, you could put this into an extension method (or even an HTML Helper extension method).
public static string ToUserFriendlyDateFormat(this string unfriendlyFormat) {
return unfriendlyFormat
.Replace("{0:", string.Empty)
.Replace("}", string.Empty);
}
I don't know what all your format strings look like, but if your format strings ever make it to String.Format() you already have to escape { and } characters (by doubling them). How about using a regular expression. Here's something simple to start with that will also undouble the { and } characters:
string DisplayFormat(string format) {
Regex rx = new Regex(#"\{\d+:([^}]+)}|\{\{|}}");
return rx.Replace(format, delegate(Match m) {
if (m.Value == "{{") {
return "{";
} else if (m.Value == "}}") {
return "}";
} else {
return m.Groups[1].Value;
}
});
}
Note that the above code will have to change if your format strings contain sequences like {0} and you want something special done with them as well.
Hope somebody has a good idea. I have strings like this:
abcdefg
abcde
abc
What I need is for them to be trucated to show like this if more than a specified lenght:
abc ..
abc ..
abc
Is there any simple C# code I can use for this?
Here is the logic wrapped up in an extension method:
public static string Truncate(this string value, int maxChars)
{
return value.Length <= maxChars ? value : value.Substring(0, maxChars) + "...";
}
Usage:
var s = "abcdefg";
Console.WriteLine(s.Truncate(3));
All very good answers, but to clean it up just a little, if your strings are sentences, don't break your string in the middle of a word.
private string TruncateForDisplay(this string value, int length)
{
if (string.IsNullOrEmpty(value)) return string.Empty;
var returnValue = value;
if (value.Length > length)
{
var tmp = value.Substring(0, length) ;
if (tmp.LastIndexOf(' ') > 0)
returnValue = tmp.Substring(0, tmp.LastIndexOf(' ') ) + " ...";
}
return returnValue;
}
public string TruncString(string myStr, int THRESHOLD)
{
if (myStr.Length > THRESHOLD)
return myStr.Substring(0, THRESHOLD) + "...";
return myStr;
}
Ignore the naming convention it's just in case he actually needs the THRESHOLD variable or if it's always the same size.
Alternatively
string res = (myStr.Length > THRESHOLD) ? myStr.Substring(0, THRESHOLD) + ".." : myStr;
Here's a version that accounts for the length of the ellipses:
public static string Truncate(this string value, int maxChars)
{
const string ellipses = "...";
return value.Length <= maxChars ? value : value.Substring(0, maxChars - ellipses.Length) + ellipses;
}
There isn't a built in method in the .NET Framework which does this, however this is a very easy method to write yourself. Here are the steps, try making it yourself and let us know what you come up with.
Create a method, perhaps an extension method public static void TruncateWithEllipsis(this string value, int maxLength)
Check to see if the passed in value is greater than the maxLength specified using the Length property. If the value not greater than maxLength, just return the value.
If we didn't return the passed in value as is, then we know we need to truncate. So we need to get a smaller section of the string using the SubString method. That method will return a smaller section of a string based on a specified start and end value. The end position is what was passed in by the maxLength parameter, so use that.
Return the sub section of the string plus the ellipsis.
A great exercise for later would be to update the method and have it break only after full words. You can also create an overload to specify how you would like to show a string has been truncated. For example, the method could return " (click for more)" instead of "..." if your application is set up to show more detail by clicking.
Code behind:
string shorten(sting s)
{
//string s = abcdefg;
int tooLongInt = 3;
if (s.Length > tooLongInt)
return s.Substring(0, tooLongInt) + "..";
return s;
}
Markup:
<td><%= shorten(YOUR_STRING_HERE) %></td>
Maybe it is better to implement a method for that purpose:
string shorten(sting yourStr)
{
//Suppose you have a string yourStr, toView and a constant value
string toView;
const int maxView = 3;
if (yourStr.Length > maxView)
toView = yourStr.Substring(0, maxView) + " ..."; // all you have is to use Substring(int, int) .net method
else
toView = yourStr;
return toView;
}
I found this question after searching for "C# truncate ellipsis". Using various answers, I created my own solution with the following features:
An extension method
Add an ellipsis
Make the ellipsis optional
Validate that the string is not null or empty before attempting to truncate it.
public static class StringExtensions
{
public static string Truncate(this string value,
int maxLength,
bool addEllipsis = false)
{
// Check for valid string before attempting to truncate
if (string.IsNullOrEmpty(value)) return value;
// Proceed with truncating
var result = string.Empty;
if (value.Length > maxLength)
{
result = value.Substring(0, maxLength);
if (addEllipsis) result += "...";
}
else
{
result = value;
}
return result;
}
}
I hope this helps someone else.
string s = "abcdefg";
if (s.length > 3)
{
s = s.substring(0,3);
}
You can use the Substring function.
Refactor with new C# features just for disclosure:
Nullables (C# 7)
Expression-bodied members (C# 6 and 7)
Ranges on strings (C# 8)
// public static class StringExtensions { ...
private static string? Truncate(this string? value, int maxChars)
=>
string.IsNullOrEmpty(value) ? value :
value.Length <= maxChars ? value :
value[..maxChars] + "...";
Checked as "Community wiki", be free to improve answer.
Sure, here is some sample code:
string str = "abcdefg";
if (str.Length > X){
str = str.Substring(0, X) + "...";
}
I has this problem recently. I was storing a "status" message in a nvarcharMAX DB field which is 4000 characters. However my status messages were building up and hitting the exception.
But it wasn't a simple case of truncation as an arbitrary truncation would orphan part of a status message, so I really needed to "truncate" at a consistent part of the string.
I solved the problem by converting the string to a string array, removing the first element and then restoring to a string. Here is the code ("CurrentStatus" is the string holding the data)...
if (CurrentStatus.Length >= 3750)
{
// perform some truncation to free up some space.
// Lets get the status messages into an array for processing...
// We use the period as the delimiter, then skip the first item and re-insert into an array.
string[] statusArray = CurrentStatus.Split(new string[] { "." }, StringSplitOptions.None)
.Skip(1).ToArray();
// Next we return the data to a string and replace any escaped returns with proper one.
CurrentStatus = (string.Join(".", statusArray))
.Replace("\\r\\n", Environment.NewLine);
}
Hope it helps someone out.