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Check a String for a Slash

string testStr="thestringhasa\slash";
if(testStr.Contains("\"))
{
//Code to process string with \
}
How do I properly test to see if a string contains a backslash, when I try the it statement if says a New Line in constant.

The other two answers are entirely correct, but no one bothered to explain why. The \ character has a special purpose in C# strings. It is the escape character, so to have a string that contains a slash, you have to use one of two methods.
Use the string literal symbol #. A string preceded by the # symbol tells the C# compiler to treat the string as a literal and not escape anything.
Use the escape character to tell the C# compiler there is a special character that is actually part of the string.
So, the following strings are equivalent:
var temp1 = #"test\test";
var test2 = "test\\test";
test1 == test2; // Yields true

You should use double slashes
string testStr=#"thestringhasa\slash";
if(testStr.Contains("\\"))
{
//Code to process string with \
}

The backslash must be escaped. Try the following:
string testStr = #"thestringhasa\slash";
if (testStr.Contains("\\"))
{
//Code to process string with \
}

String Replace "\\\" with "\"

I have a string that contains sequence of three "\" and I have to replace them with single "\".
the string is:
string sample = "<ArrayOfMyObject xmlns:i=\\\"http://www.w3.org/2001/XMLSchema-instance\\\"";
I have tried, as suggested in other threads, with the following code but it did not work:
string result = sample.Replace(#"\\\",#"\");
string result = sample.Replace("\\\\\\","\\");
thanks in advance

In your sample, your string doesn't actually have three "\" characters in it - Some of them are escape characters.
\ will actually correspond to a single \ character.
\" will actually correspond to a single " character.
The value of your string, in memory, is:-
<ArrayOfMyObject xmlns:i=\"http://www.w3.org/2001/XMLSchema-instance\"
So, your replace operations do nothing because they do not match anything.

To replace \\\ with \ in a c# string try this code (tested and working)
string strRegex = #"(\\){3}";
string strTargetString = #"sett\\\abc";
var test=Regex.Replace(strTargetString, strRegex, #"\"); //test becomes sett\abc
in debug you will see test=sett\\abc (2 backslashes but one is an escape).
Don't worry and go to text Visualizer and you'll see the correct value
then
in your specific case the code will be
string sample = #"<ArrayOfMyObject xmlns:i=\\\"http://www.w3.org/2001/XMLSchema-instance\\\"";
var result=Regex.Replace(sample , strRegex, #"\");

the output of both of the replaces is
<ArrayOfMyObject xmlns:i=\"http://www.w3.org/2001/XMLSchema-instance\"
this looks correct
but maybe you have to add 6 instead of 3 '\' in your input, because there caracters are escape characters.

split the string containing backward slash and replace with forward slash

I have a string which contains backward slashes and I want to reply it with forward slashes
string filename = "te\test";
var x = filename.Split('\\');
Console.WriteLine(filename);
Console.ReadLine();
I have tried something like this but it is getting the same string "te\test" into x.
Is there any other way to do this?

You original string is not:
te\test
it's:
te{tab}est
\t is the tab character. So you can't split on the \ because you original string doesn't have a \
If you do something like this:
string filename = "te\\test";
var x = filename.Split('\\');
Console.WriteLine(string.Join("/",x));
You'll get the result you wanted.
But you really don't need to Split and Join when you can just Replace:
Console.WriteLine(filename.Replace('\\','/'));
Note: you can use # with your original string to make it a literal string (escapes are ignored) as #Joeb454 suggests (and that's usually what I'll do), but unfortunately the same trick doesn't apply to chars so you can't, for example, do #'\'.

Your initial string appears to be wrong, you're escaping the 't', giving you a tab character, it should be string filename = "te\\test";
You could also declare it as string filename = #"te\test"; - preceding the string with the # sign indicates to the compiler that it's a literal string, and therefore nothing will be escaped.

string filename = "te\test";
string[] x = filename.Split('\\');
Console.WriteLine(filename);//this line should be Console.WriteLine(x[0]+X[1]);
Console.ReadLine();
But I think you are looking for
filename = filename.Replace("\\","/");
Console.WriteLine(filename);

Replace \\ with \ in C#

I have a long string (a path) with double backslashes, and I want to replace it with single backslashes:
string a = "a\\b\\c\\d";
string b = a.Replace(#"\\", #"\");
This code does nothing...
b remains "a\\b\\c\\d"
I also tried different combinations of backslashes instead of using #, but no luck.

Because you declared a without using #, the string a does not contain any double-slashes in your example. In fact, in your example, a == "a\b\c\d", so Replace does not find anything to replace. Try:
string a = #"a\\b\\c\\d";
string b = a.Replace(#"\\", #"\");

In C#, you can't have a string like "a\b\c\d", because the \ has a special meaning: it creates a escape sequence together with a following letter (or combination of digits).
\b represents actually a backspace, and \c and \d are invalid escape sequences (the compiler will complain about an "Unrecognized escape sequence").
So how do you create a string with a simple \? You have to use a backslash to espace the backslash:\\ (it's the espace sequence that represents a single backslash).
That means that the string "a\\b\\c\\d" actually represents a\b\c\d (it doesn't represent a\\b\\c\\d, so no double backslashes). You'll see it yourself if you try to print this string.
C# also has a feature called verbatim string literals (strings that start with #), which allows you to write #"a\b\c\d" instead of "a\\b\\c\\d".

You're wrong. "\\" return \ (know as escaping)
string a = "a\\b\\c\\d";
System.Console.WriteLine(a); // prints a\b\c\d
string b = a.Replace(#"\\", #"\");
System.Console.WriteLine(b); // prints a\b\c\d
You don't even need string b = a.Replace(#"\\", #"\");

this works
You don't even need string b = a.Replace(#"\", #"\");
but like if we generate a dos command through c# code... eg:- to delete a file
this wil help

I did this in a code in a UWP application.
foreach (var item in Attendances)
{
string a = item.ImagePath;
string b = a.Replace(#"\\", "/");
string c = a.Replace("\\", "/");
Console.WriteLine(b);
Console.WriteLine(a);
item.ImagePath = c;
}
and the ones without the # symbol is the one that actually worked. this is C# 8 and C# 9

Include "\" in a C# string

I'm trying to set the value of a string to something that has a \ in it, but cannot do so as they say I have an unrecognized escape sequence. Is it possible to write \ in a string?

You must escape it... if you are using a regular string you must double the slash "hello\\world" or if you want it as a literal you can use #"hello\world"

Yes, just change the \ to a \\.
You can read more about Escape Sequences here.

All the above answers are right. I want to include one more way of doing the same i.e. by using a unicode character.
e.g. the \u005c represents "\"
hence "hello \u005c world"; will give the output as hello \ world
All the below will give the same result
string test1 = "hello \\ world";
string test2 = #"hello \ world";
string test3 = "hello \u005c world";
For a list of unicode character set visit this site
Thanks

like others have pointed out, use double slash "\\"
OR you can change your string to a string literal, and not have to update your slashes...
eg
string a = #"some s\tring wi\th slashes";

Alternatively, you can prefix the string with #, which will tell the compiler to interpret the string literally.
string str = #"i am using \ in a string";

Yes, use "\\".
For an explanation and a list of possible escape symbols, see http://msdn.microsoft.com/en-us/library/ms228362.aspx .