Develop Reference

How could i get only the first line of an exception stack trace message in C#?

I wan't to print the stack trace message for debug purposes, but i'm only want the first line because i'm interested on getting where the problem started.
Example:
at Solution.Models.Class.Method() in C:\Users\...\Models\Class.cs:line 1118 <-- i´m only interested in this
at Solution.Models.Class.AddSomething(Something _something) in C:\Users\...\Solution\Models\Class.cs:line 518

var firstLine = originalMessage
.Split(Environment.NewLine)
.FirstOrDefault();
Where:
originalMessage - the string that you want to get the information from;
.Split() - returns a string array of the substrings that are your originalMessage divided by the passed parameter Environment.NewLine;
Environment.NewLine - gets the newline string defined for this environment. \r\n for non-Unix platforms, or \n for Unix platforms;
.FirstOrDefault() - returns the first element of a sequence, or a default value if no element is found;
This is a Linq expression that will work on all platforms, whether it is Linux, Windows or Mac due to Environment.NewLine utilization instead of hardcoded "\r\n". Also, by stacking Linq expressions one on each other you construct a certain pipeline that says:
I am taking a string;
Which I then split into substrings by a line separator;
And take the first substring from the result;

You can just substring it until the new line:
string firstLine = value.Substring(0, value.IndexOf("\r\n"));

New line character in text file (C#)

I'm exporting text to a file in C# using System.IO.File.AppendAllText, and passing in the text file, and then the text I want to export with \n added to the end. When I view the text document, they are not on different lines, although that pesky return-line character is there between the lines. So the system may think it's two line, but a user sees it as one. How can this be fixed automatically without doing a find-replace every time I generate a file?
System.IO.File.AppendAllText(#"./WarningsLog.txt", line + "\n");

You need to use the Environment.NewLine instead of \n, because newline can be more than that. in windows (if I'm not mistaken), the default is actually \r\n
Although, using \r\n, will help you temporary, using Environment.NewLine is the proper way to go

First off, there are a couple of ways to represent the new line.
The most commonly used are:
The unix way - to write the \n character. \n here represents the newline character.
The windows way - to write the \r\n characters. \r here goes for the carriage return character.
If you are writing something platform-independent, Environment.NewLine will do the job for you and pick the correct character(s).
MSDN states it represents:
A string containing "\r\n" for non-Unix platforms, or a string containing "\n" for Unix platforms.
Also, in some cases you may want to use System.IO.File.AppendAllLines that takes an IEnumerable<string> as the lines collection and appends it to the file. It uses Environment.NewLine inside.

You could try building this with some file specific characters checks , like
new line, tab , etc....
Here is an example code which checks for new line and tabs :
public static string Replace()
{
string rLower = words.ToLower().Replace(Environment.NewLine, "<replaced_newLine>");
rLower = rLower.Replace("\t", "<replaced_Tabulation>");
return rLower;
}
Of course you might have a lot of different combinations , where an item that needs to be changed is followed by " " or "\n" or "\r\n" or "\t"

System.Environment.NewLine and \n

Using Visual Studio 2010 and C#
This has worked over the many years...
string myString= txtSomeMultiLineTextBox.Text;
string str = myString.Replace(System.Environment.Newline, "<br />");
When setting a breakpoint, if myString = LineOne\nLineTwo\nLineThree
The \n is NOT replaced...
Then str = myString
There is no replace.
myString remains the same
I have researched everywhere about Environment.Newline and the differences with operating environments and the one I work with is Windows 7.
This Environment will not change.
Why is Environment.Newline not reading \n ?
Thanks,

Given that you've tagged this as asp.net I'll assume that txtSomeMultiLineTextBox is ultimately a TextArea.
TextArea returns text that is delimited either by \n or \r\n depending on the specific browser version. (IE used to always use \r\n and now uses \n, strange but true.)
So probably the reason why it used to work was because you were testing on an earlier version of IE, where \r\n was used as the new line, whereas you're now using either IE 10, 11 or Chrome, and \n is the newline.
So, to be tolerant of both situations do this:
myString.Replace("\r\n", "\n").Replace("\n", "<br />");
And just to clear this up once and for all:
Don't trust Environment.NewLine to solve this for you.
If your environment is Windows, then there is no single consistent new line used everywhere, even within Microsoft products. Better to be prepared to roll up your sleeves and normalise the line endings for yourself.

Because Environment.NewLine is platform dependent.
Environment.NewLine on non-Unix (... Windows) platforms is \r\n. That's a carriage return and line feed.
If your string contains only \n.. then it can't replace \r\n.. because that grouping isn't there.
As a test.. just replace the \n..:
string myString= txtSomeMultiLineTextBox.Text;
string str = myString.Replace("\n", "<br />");

This is because System.Environment.Newline is composed of the carriage return and the new line character ie "\r\n" so it does not match just `"\n"

C# Reading a file and writing out replacing string

What I have is a C# windows app that reads a bunch of SQL tables and creates a bunch of queries based on the results. What I'm having a small issue with is the final "," on my query
This is what I have
ColumnX,
from
I need to read the entire file, write out exactly what is in the file and just replace the last , before the from with nothing.
I tried .replace(#",\n\nfrom),(#"\n\nfrom) but it's not finding it. Any help is appreciated.
Example:
ColumnX,
from
Result:
ColumnX
from

The line break is most likely the two character combination CR + LF:
.replace(",\r\n\r\nfrom","\r\n\r\nfrom")
If you want the line break for the current system, you can use the Environment.NewLine constant:
.replace(","+Environment.NewLine+Environment.NewLine+"from",Environment.NewLine+Environment.NewLine+"from")
Note that the # in front of a string means that it doesn't use backslash escape sequences, but on the other hand it can contain line breaks, so you could write it in this somewhat confusing way:
str = str.replace(#",
from", #"
from");

There are two solutions that you can try:
Remove the # symbol, as that means it's going to look for the literal characters of \n rather than a newline.
Try .replace("," + Environment.NewLine + Environment.NewLine + from, Environment.NewLine + Environment.NewLine + "from)

Instead of replacing or removing the comma when you read the file, it would probably be preferable to remove it before the file is written. That way you only have to bother with the logic once. As you are building your column list, just remove the last comma after the list is created. Hopefully you are in a position where you have control over that process.

If you can assume you always want to remove the last occurrence of the comma you can use the string function LastIndexOf to find the index for the last comma and use Remove from there.
myString = myString.Remove(myString.LastIndexOf(","), 1);

What about using Regex? Does that handle different forms of linefeed better?
var result = Regex.Replace(input, #",(\n*)from", "$1from");

How to add line break in C# behind page

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).