Is there a bit of syntactic sugar for prefixing data to the beginning of a string in a similar way to how += appends to a string?
Just use:
x = "prefix" + x;
There's no compound assignment operator that does this.
sorry = "nope, " + sorry;
You could always write an extension method:
public static class StringExtensions{
public static string Prefix(this string str, string prefix){
return prefix + str;
}
}
var newString = "Bean".Prefix("Mr. ");
It's not syntactic sugar, but easy nonetheless. Although it is not really any simpler than what has already been suggested.
There is no =+ operator in C#, but thankfully OO comes to the rescue here:
string value = "Jamie";
value = value.Insert(0, "Hi ");
For more info on string.Insert: http://msdn.microsoft.com/en-us/library/system.string.insert.aspx
I would agree that a = b + a seems the most sensible answer here. It reads much better than using string.Insert that's for sure.
These are methods from the FCL that can be used to merge strings, without having to use any concatenation operator. The + and += operators are prone to using a lot of memory when called repeatedly (i.e. a loop) because of the nature of strings and temp strings created. (Edit: As pointed out in comments, String.Format is often not an efficient solution either)
It's more of a syntactic alternative than sugar.
string full = String.Format("{0}{1}{2}", "prefix", "main string", "last string");
^ More info on String.Format at MSDN.
Edit: Just for two strings:
string result = string.Concat("prefix", "last part");
^ More info on String.Concat.
Related
I've something like below.
var amount = "$1,000.99";
var formattedamount = string.Format("{0}{1}{0}", "\"", amount);
How can I achieve same using String interpolation?
I tried like below
var formattedamount1 = $"\"{amount}\"";
Is there any better way of doing this using string interpolation?
Update
Is there any better way of doing this using string interpolation
No, this is just string interpolation, you cant make the following any shorter and more readable really
var formattedamount1 = $"\"{amount}\"";
Original answer
$ - string interpolation (C# Reference)
To include a brace, "{" or "}", in the text produced by an
interpolated string, use two braces, "{{" or "}}". For more
information, see Escaping Braces.
Quotes are just escaped as normal
Example
string name = "Horace";
int age = 34;
Console.WriteLine($"He asked, \"Is your name {name}?\", but didn't wait for a reply :-{{");
Console.WriteLine($"{name} is {age} year{(age == 1 ? "" : "s")} old.");
Output
He asked, "Is your name Horace?", but didn't wait for a reply :-{
Horace is 34 years old.
Same thing you can achieve by doing:
var formattedamount1 = $"\"{amount}\"";
OR
var formattedamount1 = $#"""{amount}""";
It's basically allowing you to write string.Format(), but instead of using one string with "placeholders"({0}, {1}, .. {N}), you are directly writing/using your variable inside string.
Please read more about String Interpolation (DotNetPerls), $ - string interpolation to fully understand whats going on.
Just to give one more option, if you want to make sure you use the same quote at both the start and the end, you could use a separate variable for that:
string quote = "\"";
string amount = "$1,000.99";
string formattedAmount = $"{quote}{amount}{quote}";
I'm not sure I'd bother with that personally, but it's another option to consider.
For example I have a
String a="Hello";
a+="World";
this would put World at the end. How can I put it at the beginning?
Simply:
string a = "Hello";
a = "World" + a;
Ultimately, a += "World"; is just abbreviated syntax for:
a = a + "World";
No such abbreviation exists if you want to reverse the order of the operands.
As a side note - keep in mind that if you are doing this a lot (in a loop etc) it may be better to consider StringBuilder to avoid lots of intermediary strings.
You can also call the Insert function;
a = a.Insert(0, "start");
To prepend, you'd simply use.
a = "World" + a;
Please bear in mind that actually, you'd be creating a completely new string, you can't pre or postpend any string in C# as they are immutable. Consider using String.Format or StringBuilder.AppendFormat if you have special string processing needs.
Just do this:
String a = "Hello";
a = "World " + a;
Just use
string a = "Hello";
a = "World" + a;
Because a+= "World"; is equavalent with;
a = a + "World";
Check out for more information How to: Concatenate Multiple Strings (C# Programming Guide)
Hint: This is not in this case but if performance is important, you should always use the StringBuilder class to concatenate strings. It represents mutable strings.
it's simple you can add the new word in the begin
String a="Hello";
a="World" + a;
You can't do that with any special operator. You will have to do:
a = "World"+a;
Use StringBuilder to perform string operations.
http://msdn.microsoft.com/en-us/library/2839d5h5(v=vs.71).aspx
string str = 'my {0} long string {1} need formatting';
Should I be doing the following,
str = string.Format(str, "really", "doesn't");
or creating a method like so and calling str = str.ReplaceWithValues("really", "doesn't");
public string ReplaceWithValues(this string str, params object[] values) {
string ret = str;
for (int i = 0; i < values.Length; i++) {
ret = str.Replace(string.Concat("{", i, "}"), values.ToString());
}
return ret;
}
It seems like StringBuilder.AppendFormat() isn't efficient when it comes to doing simple replacements like this since it goes character by character through the string.
Why do you want to reinvent String.Format?
I'd just use the framework method - it does exactly what you want, is robust, and is going to make sense to those that follow...
Just to satisfy your curiousity:
It seems like StringBuilder.AppendFormat() isn't efficient when it comes to doing simple replacements like this since it goes character by character through the string.
String.Format, FYI, uses StringBuilder.AppendFormat internally. That being said, StringBuilder.AppendFormat is quite efficient. You mention that it goes "character by character" through the string - however, in your case, you're using multiple calls to Replace and Concat instead. A single pass through the string with a StringBuilder is likely to be much quicker. If you really need to know- you could profile this to check. On my machine, I get the following timings if I run both of the above 1,000,000 times:
String.Format - 1029464 ticks
Custom method - 2988568 ticks
The custom procedure will increase its cost with each additional placeholder and produce throwaway strings for the garbage collector with each intermediate call to Replace.
Besides the likelihood that string.Format is much faster than multiple calls to Replace, string.Format includes overloads to culture-sensitive operations as well.
The flexibility and intuitiveness of string.Format is at least as compelling as the speed.
If all you want is to concatenate some strings, why not just do that?
string result = "my " + x + " long string " + y + " need formatting";
or
string result = string.Concat("my ", x, " long string ", y, " need formatting");
In C# the + operator actually turns in to a string.Concat(), and I always thought String.Format("Hello: {0} {1}", "Bob", "Jones") was the fastest. It turns out, after firing up a sample ran outside the debugger, in release mode, that "Bob" + "Jones" is much faster. There is a cutoff point though. I believe around 8 concatenations or so, string.Format becomes faster.
I don't want to do any rounding, straight up, "39%".
So "9.99%" should become "9%".
I hope this will work.
string str = "39.999%";
string[] Output = str.Split('.');
Output[0] will have your Answer.
Thanks
string myPercentage = "48.8983%";
string newString = myPercentage.Replace("%","");
int newNumber = (int)Math.Truncate(Double.Parse(newString));
Console.WriteLine(newNumber + "%");
There maybe hundred ways of doing this and this is just one :)
Probably a Regex. I'm no master of regular expressions, I generally avoid them like the plague, but this seems to work.
string num = "39.988%";
string newNum = Regex.Replace(num, #"\.([0-9]+)%", "%");
One way to do it:
"39.999%".Split(new char[] { '.' })[0] + "%";
int.Parse("39.999%".Split('.')[0])
Doing this gives you a nice int that you can work with as you see fit. You can stick a % sign on the end with whatever string concatenation floats your boat.
Now we have two questions asking the same thing..
Heres my crack at it.
"39.9983%".Split('.')[0] + "%";
Console.WriteLine("{0}%", (int)39.9983);
I'm guessing you want a string returned? Probably the laziest way to do it:
string mynum = "39.999%"
mynum = mynum.substring(0, mynum.IndexOf('.'));
mynum += "%";
To get an int, you could cast the result of line 2.
Are there differences between these examples? Which should I use in which case?
var str1 = "abc" + dynamicString + dynamicString2;
var str2 = String.Format("abc{0}{1}", dynamicString, dynamicString2);
var str3 = new StringBuilder("abc").
Append(dynamicString).
Append(dynamicString2).
ToString();
var str4 = String.Concat("abc", dynamicString, dynamicString2);
There are similar questions:
Difference in String concatenation which only asks about the + operator, and it's not even mentioned in the answer that it is converted to String.Concat
What's the best string concatenation method which is not really related to my question, where it is asking for the best, and not a comparation of the possible ways to concatenate a string and their outputs, as this question does.
This question is asking about what happens in each case, what will be the real output of those examples? What are the differences about them? Where should I use them in which case?
As long as you are not deailing with very many (100+) strings or with very large (Length > 10000) strings, the only criterion is readability.
For problems of this size, use the +. That + overload was added to the string class for readability.
Use string.Format() for more complicated compositions and when substitutions or formatting are required.
Use a StringBuilder when combining many pieces (hundreds or more) or very large pieces (length >> 1000). StringBuilder has no readability features, it's just there for performance.
Gathering information from all the answers it turns out to behave like this:
The + operator is the same as the String.Concat, this could be used on small concatenations outside a loop, can be used on small tasks.
In compilation time, the + operator generate a single string if they are static, while the String.Concat generates the expression str = str1 + str2; even if they are static.
String.Format is the same as StringBuilder.. (example 3) except that the String.Format does a validation of params and instantiate the internal StringBuilder with the length of the parameters.
String.Format should be used when format string is needed, and to concat simple strings.
StringBuilder should be used when you need to concatenate big strings or in a loop.
Use the + operator in your scenario.
I would only use the String.Format() method when you have a mix of variable and static data to hold in your string. For example:
string result=String.Format(
"Today {0} scored {1} {2} and {3} points against {4}",..);
//looks nicer than
string result = "Today " + playerName + " scored " + goalCount + " " +
scoreType + " and " + pointCount + " against " + opposingTeam;
I don't see the point of using a StringBuilder, since you're already dealing with three string literals.
I personally only use Concat when dealing with a String array.
My rule of thumb is to use String.Format if you are doing a relatively small amount of concatination (<100) and StringBuilder for times where the concatination is going to be large or is potentially going to be large. I use String.Join if I have an array and there isn't any formatting needed.
You can also use the Aggregate function in LINQ if you have an enumerable collection:
http://msdn.microsoft.com/en-us/library/bb548651.aspx
# Jerod Houghtelling Answer
Actually String.Format uses a StringBuilder behind the scenes (use reflecton on String.Format if you want)
I agree with the following answer in general
#Xander. I believe you man. However my code shows sb is faster than string.format.
Beat this:
Stopwatch sw = new Stopwatch();
sw.Start();
for (int i = 0; i < 10000; i++)
{
string r = string.Format("ABC{0}{1}{2}", i, i-10,
"dasdkadlkdjakdljadlkjdlkadjalkdj");
}
sw.Stop();
Console.WriteLine("string.format: " + sw.ElapsedTicks);
sw.Reset();
sw.Start();
for (int i = 0; i < 10000; i++)
{
StringBuilder sb = new StringBuilder();
string r = sb.AppendFormat("ABC{0}{1}{2}", i, i - 10,
"dasdkadlkdjakdljadlkjdlkadjalkdj").ToString();
}
sw.Stop();
Console.WriteLine("AppendFormat: " + sw.ElapsedTicks);
It's important to understand that strings are immutable, they don't change. So ANY time that you change, add, modify, or whatever a string - it is going to create a new 'version' of the string in memory, then give the old version up for garbage collection. So something like this:
string output = firstName.ToUpper().ToLower() + "test";
This is going to create a string (for output), then create THREE other strings in memory (one for: ToUpper(), ToLower()'s output, and then one for the concatenation of "test").
So unless you use StringBuilder or string.Format, anything else you do is going to create extra instances of your string in memory. This is of course an issue inside of a loop where you could end up with hundreds or thousands of extra strings. Hope that helps
It is important to remember that strings do not behave like regular objets.
Take the following code:
string s3 = "Hello ";
string s3 += "World";
This piece of code will create a new string on the heap and place "Hello" into it. Your string object on the stack will then point to it (just like a regular object).
Line 2 will then creatre a second string on the heap "Hello World" and point the object on the stack to it. The initial stack allocation still stands until the garbage collector is called.
So....if you have a load of these calls before the garbage collector is called you could be wasting a lot of memory.
I see that nobody know this method:
string Color = "red";
Console.WriteLine($"The apple is {Color}");
var str3 = new StringBuilder
.AppendFormat("abc{0}{1}", dynamicString, dynamicString2).ToString();
the code above is the fastest. so use if you want it fast. use anything else if you dont care.