Is there an easy way to create a multiline string literal in C#?
Here's what I have now:
string query = "SELECT foo, bar"
+ " FROM table"
+ " WHERE id = 42";
I know PHP has
<<<BLOCK
BLOCK;
Does C# have something similar?
You can use the # symbol in front of a string to form a verbatim string literal:
string query = #"SELECT foo, bar
FROM table
WHERE id = 42";
You also do not have to escape special characters when you use this method, except for double quotes as shown in Jon Skeet's answer.
It's called a verbatim string literal in C#, and it's just a matter of putting # before the literal. Not only does this allow multiple lines, but it also turns off escaping. So for example you can do:
string query = #"SELECT foo, bar
FROM table
WHERE name = 'a\b'";
This includes the line breaks (using whatever line break your source has them as) into the string, however. For SQL, that's not only harmless but probably improves the readability anywhere you see the string - but in other places it may not be required, in which case you'd either need to not use a multi-line verbatim string literal to start with, or remove them from the resulting string.
The only bit of escaping is that if you want a double quote, you have to add an extra double quote symbol:
string quote = #"Jon said, ""This will work,"" - and it did!";
As a side-note, with C# 6.0 you can now combine interpolated strings with the verbatim string literal:
string camlCondition = $#"
<Where>
<Contains>
<FieldRef Name='Resource'/>
<Value Type='Text'>{(string)parameter}</Value>
</Contains>
</Where>";
The problem with using string literal I find is that it can make your code look a bit "weird" because in order to not get spaces in the string itself, it has to be completely left aligned:
var someString = #"The
quick
brown
fox...";
Yuck.
So the solution I like to use, which keeps everything nicely aligned with the rest of your code is:
var someString = String.Join(
Environment.NewLine,
"The",
"quick",
"brown",
"fox...");
And of course, if you just want to logically split up lines of an SQL statement like you are and don't actually need a new line, you can always just substitute Environment.NewLine for " ".
One other gotcha to watch for is the use of string literals in string.Format. In that case you need to escape curly braces/brackets '{' and '}'.
// this would give a format exception
string.Format(#"<script> function test(x)
{ return x * {0} } </script>", aMagicValue)
// this contrived example would work
string.Format(#"<script> function test(x)
{{ return x * {0} }} </script>", aMagicValue)
Why do people keep confusing strings with string literals? The accepted answer is a great answer to a different question; not to this one.
I know this is an old topic, but I came here with possibly the same question as the OP, and it is frustrating to see how people keep misreading it. Or maybe I am misreading it, I don't know.
Roughly speaking, a string is a region of computer memory that, during the execution of a program, contains a sequence of bytes that can be mapped to text characters. A string literal, on the other hand, is a piece of source code, not yet compiled, that represents the value used to initialize a string later on, during the execution of the program in which it appears.
In C#, the statement...
string query = "SELECT foo, bar"
+ " FROM table"
+ " WHERE id = 42";
... does not produce a three-line string but a one liner; the concatenation of three strings (each initialized from a different literal) none of which contains a new-line modifier.
What the OP seems to be asking -at least what I would be asking with those words- is not how to introduce, in the compiled string, line breaks that mimick those found in the source code, but how to break up for clarity a long, single line of text in the source code without introducing breaks in the compiled string. And without requiring an extended execution time, spent joining the multiple substrings coming from the source code. Like the trailing backslashes within a multiline string literal in javascript or C++.
Suggesting the use of verbatim strings, nevermind StringBuilders, String.Joins or even nested functions with string reversals and what not, makes me think that people are not really understanding the question. Or maybe I do not understand it.
As far as I know, C# does not (at least in the paleolithic version I am still using, from the previous decade) have a feature to cleanly produce multiline string literals that can be resolved during compilation rather than execution.
Maybe current versions do support it, but I thought I'd share the difference I perceive between strings and string literals.
UPDATE:
(From MeowCat2012's comment) You can. The "+" approach by OP is the best. According to spec the optimization is guaranteed: http://stackoverflow.com/a/288802/9399618
Add multiple lines : use #
string query = #"SELECT foo, bar
FROM table
WHERE id = 42";
Add String Values to the middle : use $
string text ="beer";
string query = $"SELECT foo {text} bar ";
Multiple line string Add Values to the middle: use $#
string text ="Customer";
string query = $#"SELECT foo, bar
FROM {text}Table
WHERE id = 42";
You can use # and "".
string sourse = #"{
""items"":[
{
""itemId"":0,
""name"":""item0""
},
{
""itemId"":1,
""name"":""item1""
}
]
}";
In C# 11 [2022], you will be able to use Raw String literals.
The use of Raw String Literals makes it easier to use " characters without having to write escape sequences.
Solution for OP:
string query1 = """
SELECT foo, bar
FROM table
WHERE id = 42
""";
string query2 = """
SELECT foo, bar
FROM table
WHERE id = 42
and name = 'zoo'
and type = 'oversized "jumbo" grand'
""";
More details about Raw String Literals
See the Raw String Literals GitHub Issue for full details; and Blog article C# 11 Preview Updates – Raw string literals, UTF-8 and more!
I haven't seen this, so I will post it here (if you are interested in passing a string you can do this as well.) The idea is that you can break the string up on multiple lines and add your own content (also on multiple lines) in any way you wish. Here "tableName" can be passed into the string.
private string createTableQuery = "";
void createTable(string tableName)
{
createTableQuery = #"CREATE TABLE IF NOT EXISTS
["+ tableName + #"] (
[ID] INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
[Key] NVARCHAR(2048) NULL,
[Value] VARCHAR(2048) NULL
)";
}
Yes, you can split a string out onto multiple lines without introducing newlines into the actual string, but it aint pretty:
string s = $#"This string{
string.Empty} contains no newlines{
string.Empty} even though it is spread onto{
string.Empty} multiple lines.";
The trick is to introduce code that evaluates to empty, and that code may contain newlines without affecting the output. I adapted this approach from this answer to a similar question.
There is apparently some confusion as to what the question is, but there are two hints that what we want here is a string literal not containing any newline characters, whose definition spans multiple lines. (in the comments he says so, and "here's what I have" shows code that does not create a string with newlines in it)
This unit test shows the intent:
[TestMethod]
public void StringLiteralDoesNotContainSpaces()
{
string query = "hi"
+ "there";
Assert.AreEqual("hithere", query);
}
Change the above definition of query so that it is one string literal, instead of the concatenation of two string literals which may or may not be optimized into one by the compiler.
The C++ approach would be to end each line with a backslash, causing the newline character to be escaped and not appear in the output. Unfortunately, there is still then the issue that each line after the first must be left aligned in order to not add additional whitespace to the result.
There is only one option that does not rely on compiler optimizations that might not happen, which is to put your definition on one line. If you want to rely on compiler optimizations, the + you already have is great; you don't have to left-align the string, you don't get newlines in the result, and it's just one operation, no function calls, to expect optimization on.
If you don't want spaces/newlines, string addition seems to work:
var myString = String.Format(
"hello " +
"world" +
" i am {0}" +
" and I like {1}.",
animalType,
animalPreferenceType
);
// hello world i am a pony and I like other ponies.
You can run the above here if you like.
using System;
namespace Demo {
class Program {
static void Main(string[] args) {
string str = #"Welcome User,
Kindly wait for the image to
load";
Console.WriteLine(str);
}
}
}
Output
Welcome User,
Kindly wait for the image to
load
Related
In my C# application I concatenate form data into a string format to be passed over to a format expected by a webservice.
string firstName = "Test";
string lastName = "Test";
string freeText = "this is some free text, thanks";
string submitString = firstName + "," + lastName + "," + freeText;
Later in the application I need to pick this apart when it is returned from the webservice to be used somewhere else.
string[] returnData = submitString.Split(',');
However if free text contains a comma, the returnData variable splits it as part of the string array and I would like to keep the contents of freeText as one whole string (despite containing a comma).
Is there a quick way I can ignore the contents of that field in the string split (rather than stopping the customer entering a comma).
If the following two conditions are satisfied:
there is a fixed number of "fields" in your comma-separated string (e.g. 3) and
only the last one can contain additional commas,
Then, yes, you can use the String.Split(char[], int) overload to specify the maximum number of items to return:
var s = "Test,Test,this is some free text, thanks";
var a = s.Split(new[] {','}, 3); // return at most 3 items
Console.WriteLine(a[0]); // prints Test
Console.WriteLine(a[1]); // prints Test
Console.WriteLine(a[2]); // prints this is some free text, thanks
Otherwise, the answer is "no", because String.Split has no way to see a difference between a "field-separating comma" and a "user-entered comma". How would it know to split Test,Test,free text, thanks,Test as Test/Test/free text, thanks/Test or Test/Test/free text/ thanks,Test?
However, there are a few other ways to solve this problem:
What you have is essentially a string with "comma-separated values" (CSV). If you use a professional CSV library (instead of String.Join/String.Split), values that contain commas will be quoted, and those commas will be ignored when extracting the values.
An easier solution might be to use a different string format altogether: If you encode your values in a JSON array instead of a CSV string, the JSON library will take care of encoding/decoding values that include special characters.
Obviously, if you can avoid encoding all values in a single string at all and just use an array or some other data structure instead, the problem would just disappear. However, there is not enough background in your question to know whether this is a viable option.
Hello i have maybe stupid question, how can i write for example
this line of code, which may represent big sql statement (dozens of rows)
string sql = "SELECT A,B,C FROM TableX";
to following block code format, which is more transparent, simpler to edit but i need also to have one line string ?
string sql = "SELECT A,
B,
C
FROM
TableX";
But i dont want to have \n characters in the string, i want that block was also ONE LINE string.
Thank you
You could add # in front of the string. This turns it into a verbatim string which is allowed to span multiple lines.
This does introduce line breaks (and possible lots of extra spaces, depending on indention), but you can easily remove those.
I have this problem where String.Contains returns true and String.LastIndexOf returns -1. Could someone explain to me what happened? I am using .NET 4.5.
static void Main(string[] args)
{
String wikiPageUrl = #"http://it.wikipedia.org/wiki/ʿAbd_Allāh_al-Sallāl";
if (wikiPageUrl.Contains("wikipedia.org/wiki/"))
{
int i = wikiPageUrl.LastIndexOf("wikipedia.org/wiki/");
Console.WriteLine(i);
}
}
While #sa_ddam213's answer definitely fixes the problem, it might help to understand exactly what's going on with this particular string.
If you try the example with other "special characters," the problem isn't exhibited. For example, the following strings work as expected:
string url1 = #"http://it.wikipedia.org/wiki/»Abd_Allāh_al-Sallāl";
Console.WriteLine(url1.LastIndexOf("it.wikipedia.org/wiki/")); // 7
string url2 = #"http://it.wikipedia.org/wiki/~Abd_Allāh_al-Sallāl";
Console.WriteLine(url2.LastIndexOf("it.wikipedia.org/wiki/")); // 7
The character in question, "ʿ", is called a spacing modifier letter1. A spacing modifier letter doesn't stand on its own, but modifies the previous character in the string, this case a "/". Another way to put this is that it doesn't take up its own space when rendered.
LastIndexOf, when called with no StringComparison argument, compares strings using the current culture.
When strings are compared in a culture-sensitive manner, the "/" and "ʿ" characters are not seen as two distinct characters--they're processed into one character, which does not match the parameter passed in to LastIndexOf.
When you pass in StringComparison.Ordinal to LastIndexOf, the characters are treated as distinct, due to the nature of Ordinal comparison.
Another way to make this work would be to use CompareInfo.LastIndexOf and supply the CompareOptions.IgnoreNonSpace option:
Console.WriteLine(
CultureInfo.CurrentCulture.CompareInfo.LastIndexOf(
wikiPageUrl, #"it.wikipedia.org/wiki/", CompareOptions.IgnoreNonSpace));
// 7
Here we're saying that we don't want combining characters included in our string comparison.
As a sidenote, this means that #Partha's answer and #Noctis' answer only work because the character is being applied to a character that doesn't appear in the search string that's passed to LastIndexOf.
Contrast this with the Contains method, which by default performs an Ordinal (case sensitive and culture insensitive) comparison. This explains why Contains returns true and LastIndexOf returns false.
For a fantastic overview of how strings should be manipulated in the .NET framework, check out this article.
1: Is this different than a combining character or is it a type of combining character? would appreciate if someone would clear that up for me.
Try using StringComparison.Ordinal
This will compare the string by evaluating the numeric values of the corresponding chars in each string, this should work with the special chars you have in that example string
string wikiPageUrl = #"http://it.wikipedia.org/wiki/ʿAbd_Allāh_al-Sallāl";
int i = wikiPageUrl.LastIndexOf("http://it.wikipedia.org/wiki/", StringComparison.Ordinal);
// returns 0;
The thing is C# lastindexof looks from behind.
And wikipedia.org/wiki/ is followed by ' which it takes as escape sequence. So either remove ' after wiki/ or have an # there too.
The following syntax will work( anyone )
string wikiPageUrl = #"http://it.wikipedia.org/wiki/Abd_Allāh_al-Sallāl";
string wikiPageUrl = #"http://it.wikipedia.org/wiki/#ʿAbd_Allāh_al-Sallāl";
int i = wikiPageUrl.LastIndexOf("wikipedia.org/wiki");
All 3 works
If you want a generalized solution for this problem replace ' with #' in your string before you perform any operations.
the ' characters throws it off.
This should work, when you escape the ' as \':
wikiPageUrl = #"http://it.wikipedia.org/wiki/\'Abd_Allāh_al-Sallāl";
if (wikiPageUrl.Contains("wikipedia.org/wiki/"))
{
"contains".Dump();
int i = wikiPageUrl.LastIndexOf("wikipedia.org/wiki/");
Console.WriteLine(i);
}
figure out what you want to do (remove the ', escape it, or dig deeper :) ).
I have written code in C# which is exceeding page width, so I want it to be broken into next line according to my formatting. I tried to search a lot to get that character for line break but was not able to find out.
In VB.NET I use '_' for line break, same way what is used in C#?
I am trying to break a string.
In C# there's no 'new line' character like there is in VB.NET. The end of a logical 'line' of code is denoted by a ';'. If you wish to break the line of code over multiple lines, just hit the carriage return (or if you want to programmatically add it (for programmatically generated code) insert 'Environment.NewLine' or '\r\n'.
Edit: In response to your comment: If you wish to break a string over multiple lines (i.e. programmatically), you should insert the Environment.NewLine character. This will take the environment into account in order to create the line ending. For instance, many environments, including Unix/Linux only use a NewLine character (\n), but Windows uses both carriage return and line feed (\r\n). So to break a string you would use:
string output = "Hello this is my string\r\nthat I want broken over multiple lines."
Of course, this would only be good for Windows, so before I get flamed for incorrect practice you should actually do this:
string output = string.Format("Hello this is my string{0}that I want broken over multiple lines.", Environment.NewLine);
Or if you want to break over multiple lines in your IDE, you would do:
string output = "My string"
+ "is split over"
+ "multiple lines";
Option A: concatenate several string literal into one:
string myText = "Looking up into the night sky is looking into infinity" +
" - distance is incomprehensible and therefore meaningless.";
Option B: use a single multiline string literal:
string myText = #"Looking up into the night sky is looking into infinity
- distance is incomprehensible and therefore meaningless.";
With option B, the newline character(s) will be part of the string saved into variable myText. This might, or might not, be what you want.
result = "Minimum MarketData"+ Environment.NewLine
+ "Refresh interval is 1";
Use # symbol before starting the string.
like
string s = #"this is a really
long string
and this is
the rest of it";
If I am understanding this correctly, you should be able to break the string into substrings to accomplish this.
i.e.:
string s = "this is a really long string" +
"and this is the rest of it";
C# doesn't have an explicit line break character. You statements end with a semicolon so you can span your statements over many lines. These are both the same:
public string GenerateString()
{
return "abc" + "def";
}
public string GenerateString()
{
return
"abc" +
"def";
}
All you need to do is add \n or to write on files go \r\n.
Examples:
say you wanted to write duck(line break) cow this is how you would do it
Console.WriteLine("duck\n cow");
Edit: I think I didn't understand the question. You can use
#"duck
cow".Replace("\r\n", "")
as a linebreak in code, that produces \r\n which is used Windows.
C# code can be split between lines on pretty much any syntatic construct without a need for a '_' style construct.
For example
foo.
Bar(
42
, "again");
dt = abj.getDataTable(
"select bookrecord.userid,usermaster.userName, "
+" book.bookname,bookrecord.fromdate, "
+" bookrecord.todate,bookrecord.bookstatus "
+" from book,bookrecord,usermaster "
+" where bookrecord.bookid='"+ bookId +"' "
+" and usermaster.userId=bookrecord.userid "
+" and book.bookid='"+ bookId +"'");
guys.. use resources for long strings in code behind!!
also.. you don't need an _ for codeline breaks in C#. In VB the codelines end with a newline character (or a ':'), using the the _ would tell the parser it has not reached the end of the line yet. The codeline in C# ends with a ';' so you can use newlines to styleformat your code.
Strings are immutable, so using
public string GenerateString()
{
return
"abc" +
"def";
}
will slow you performance - each of those values is a string literal which must be concatenated at runtime - bad news if you reuse the method/property/whatever alot...
Store your string literals in resources is a good idea...
public string GenerateString()
{
return Resources.MyString;
}
That way it is localisable and the code is tidy (although performance is pretty terrible).
A string variable str contains the following somewhere inside it: se\">
I'm trying to find the beginning of it using:
str.IndexOf("se\\\">")
which returns -1
Why isn't it finding the substring?
Note: due to editing the snippet showed 5x \ for a while, the original had 3 in a row.
Your code is in fact searching for 'se\\">'. When searching for strings including backslashes I usually find it easier to use verbatim strings:
str.IndexOf(#"se\"">")
In this case you also have a quote in the search string, so there is still some escaping, but I personally find it easier to read.
Update: my answer was based on the edit that introduced extra slashes in the parameter to the IndexOf call. Based on current version, I would place my bet on str simply not containing the expected character sequence.
Update 2:
Based on the comments on this answer, it seems to be some confusion regarding the role of the '\' character in the strings. When you inspect a string in the Visual Studio debugger, it will be displayed with escaping characters.
So, if you have a text box and type 'c:\' in it, inspecting the Text property in the debugger will show 'c:\\'. An extra backslash is added for escaping purposes. The actual string content is still 'c:\' (which can be verified by checking the Length property of the string; it will be 3, not 4).
If we take the following string (taken from the comment below)
" '<em
class=\"correct_response\">a
night light</em><br
/><br /><table
width=\"100%\"><tr><td
class=\"right\">Ingrid</td></tr></table>')"
...the \" sequences are simply escaped quotation marks; the backslashes are not part of the string content. So, you are in fact looking for 'se">', not 'se\">'. Either of these will work:
str.IndexOf(#"se"">"); // verbatim string; escape quotation mark by doubling it
str.IndexOf("se\">"); // regular string; escape quotation mark using backslash
This works:
string str = "<case\\\">";
int i = str.IndexOf("se\\\">"); // i = 3
Maybe you're not correctly escaping one of the two strings?
EDIT there's an extra couple of \ in the string you are searching for.
Maybe the str variable does not actually contain the backslash.
It may be just that when you mouse over the variable while debugging, the debugger tooltip will show the escape character.
e.g. If you put a breakpoint after this assignment
string str = "123\"456";
the tooltip will show 123\"456 and not 123"456.
However if you click on the visualize icon, you will get the correct string 123"456
Following code:
public static void RunSnippet()
{
string s = File.ReadAllText (#"D:\txt.txt");
Console.WriteLine (s);
int i = s.IndexOf("se\\\">");
Console.WriteLine (i);
}
Gives following output:
some text before se\"> some text after
17
Seems like working to me...
TextBox2.Text = TextBox1.Text.IndexOf("se\"">")
seems to work in VB.
DoubleQuotes within a string need to be specified like "" Also consider using verbatim strings - So an example would be
var source = #"abdefghise\"">jklmon";
Console.WriteLine(source.IndexOf(#"se\"">")); // returns 8
If you are looking for se\">
then
str.IndexOf(#"se\"">")
is less error-prone. Note the double "" and single \
Edit, after the comment: it seems like the string may contain ecaping itself, in which case in se\"> the \" was an escaped quote, so the literal text is simply se"> and the string to use is Indexof("se\">")