I need to initialize a string with a long string value. The string cannot have any line breaks (it will be word wrapped).
I know I can do this:
string s = "Here is part of a very long string " +
"Here is more of it here as well " +
"and it continues on to this line as well.";
But what does this do? Is it using concatenation at run time or is the compiler smart enough to know it's all one string?
Does anyone know how to declare a string like this without run-time concatenation? I was hoping the backslash could escape the new line somehow, but that's not valid. The verbatim identifier (#"") doesn't help here because that just makes the line breaks part of the string.
As pointed out by #Crowcoder, the Microsoft Documentation does in fact covert this exact question.
The following example splits a long string literal into smaller strings to improve readability in the source code. The code concatenates the smaller strings to create the long string literal. The parts are concatenated into a single string at compile time. There's no run-time performance cost regardless of the number of strings involved.
I've a problem where I want to replace some specific single quotes with double quotes inside a SQL string but not all singles quotes in that string.
EXEC procedureName 'param'eter1', 'parameter2'
In above example I just want to replace the singles quotes inside the 'param'eter1' but the singles quotes in start and end of the parameter to remain same.
Using below command replace all singles quotes in the string and it looks like this ''param''eter1'' which is not correct.
sometext.Replace("'", "''")
I want it to look like this:
EXEC procedureName 'param''eter1', 'parameter2'
Also please note that I am already aware that using SqlParameter is a better solution to handle the single quotes in SQL parameters but due to the restrictions in the project environment I am unable to implement that.
Update:
Changing the individual parameters before using them to construct the full statement is not an option for me as I don't have access to that code. My project works like a data layer where it received SQL strings from other applications to process.
This is a very bad idea. The SQL syntax requires you to escape single quotes in literals exactly because it can otherwise not tell whether the single quote is meant to represent a single quote or meant to terminate the string literal.
Consider the following example:
EXEC procedureName 'param ', ' eter1', 'parameter2'
How would you know whether this is meant to have three parameters for the procedure call or only two? And even if you knew that this specific procedure takes two parameters, you couldn't decide whether the middle part belongs to the first or second parameter.
If the system constructs sql statements from user input without dealing with single quotes before the full statement is constructed, this can be used very easily to attack the system via an sql injection.
you can do like this
var aStringBuilder = new StringBuilder(theString);
aStringBuilder.Remove(3, 2); // just find a position of single quotes
aStringBuilder.Insert(3, "/""); // replace that position with " quotes using loop
theString = aStringBuilder.ToString();
In our C# desktop-application we generate a lot of dynamic sql-queries. Now we have some troubles with single quotes in strings. Here's a sample:
INSERT INTO Addresses (CompanyName) VALUES ('Thomas' Imbiss')
My question is: How can I find and replace all single quotes between 2 other single quotes in a string? Unfortunately I can't replace the single quotes when creating the different queries. I can only do that after the full query is created and right before the query gets executed.
I tried this pattern (Regular Expressions): "\w\'\w"
But this pattern doesn't work, because after "s'" there's a space instead of a char.
I am sorry to say, there is no solution in approach you expect.
For example, have these columns and values:
column A, value ,A',
column B, value ,B',
If they are together in column list, you have ',A',',',B','.
Now, where is the boundary between first and second value? It is ambiguous.
You must take action when creating text fields for SQL. Either use SQL parameters or properly escape qoutes and other problematic characters there.
Consider showing the above ambiguous example to managers, pushing the whole problem back as algorithmically unsolvable at your end. Or offer implementing a guess-work and ask them whether they will be happy if content of several text fields can get mixed in some cases like above one.
At time of SQL query creation, if they do not want to start using SQL parameters, the solution for enquoting any input string is as simple as replacing:
string Enquote(string input)
{
return input.All(c => Strings.AscW(c) < 128) ? "'" : "N'"
+ input.Replace("'", "''")
+ "'"
}
Of course, it can have problem with deliberately malformed Unicode strings (surrogate pairs to hide ') but it is not normally possible to produce these strings through the user interface. Generally this can be still faster than converting all queries to versions with SQL parameters.
I have a path that is named defaultPath I want to add it into this verbatim string literal but can quite get the quotes around it.
#"""C:\Mavro\MavBridge\Server\MavBridgeService.exe"" /service /data ""..\Data"""
I was trying to add +defaultPath to replace Data. So lets say I have a folder name Data.Apple I want the output to be
"C:\Mavro\MavBridge\Server\MavBridgeService.exe" /service /data "..\Data.Apple"
But when I have been doing it for the past half hour I have been getting
"C:\Mavro\MavBridge\Server\MavBridgeService.exe" /service /data "..\"Data.Apple
or
"C:\Mavro\MavBridge\Server\MavBridgeService.exe" /service /data "..\" + defaultPath
Do it like this (preferred):
string.Format(#"""C:\Mavro\MavBridge\Server\MavBridgeService.exe"" /service /data ""..\{0}""", defaultPath);
Or like this:
#"""C:\Mavro\MavBridge\Server\MavBridgeService.exe"" /service /data ""..\" + defaultPath + "\"";
The first one uses string.Format, which basically replaces the {0} in the first parameter with the value in the second parameter and returns the result.
The second one uses classical string concatenation and what I did there was to remove the double quotes after the last backslash (""..\ instead of ""..\""), because you didn't want the quotes after the backslash. You wanted the quotes after defaultPath. And that's what this code does: It appends defaultPath (" + defaultPath) and appends the closing quote afterwards (+ "\"").
So if you would like to take advantage of the string interpolation with c# 6 you could also do
var randomText = "insert something";
var yourString = $#"A bunch of text in here
that is on seperate lines
but you want to {randomText }";
Use string.Format to insert the variable between the quotes:
string path = "Data.Apple";
string verbatim = string.Format(#"""C:\Mavro\MavBridge\Server\MavBridgeService.exe"" /service /data ""{0}""", path);
MessageBox.Show(verbatim);
It makes it easier to read and to implement, you can replace other portions of the path with variable sections in a similar manner.
If you try to just append the "defaultPath" variable to the end, it will never work correctly, as you've already added the closing ".
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