Develop Reference

How to extract name from a file name in the form "<name>_<fileNum>of<fileNumTotal>" or "<name>"?

a user specifies a file name that can be either in the form "<name>_<fileNum>of<fileNumTotal>" or simply "<name>". I need to somehow extract the "<name>" part from the full file name.
Basically, I am looking for a solution to the method "ExtractName()" in the following example:
string fileName = "example_File"; \\ This var is specified by user
string extractedName = ExtractName(fileName); // Must return "example_File"
fileName = "example_File2_1of5";
extractedName = ExtractName(fileName); // Must return "example_File2"
fileName = "examp_File_3of15";
extractedName = ExtractName(fileName); // Must return "examp_File"
fileName = "example_12of15";
extractedName = ExtractName(fileName); // Must return "example"
Edit: Here's what I've tried so far:
ExtractName(string fullName)
{
return fullName.SubString(0, fullName.LastIndexOf('_'));
}
But this clearly does not work for the case where the full name is just "<name>".
Thanks

This would be easier to parse using Regex, because you don't know how many digits either number will have.
var inputs = new[]
{
"example_File",
"example_File2_1of5",
"examp_File_3of15",
"example_12of15"
};
var pattern = new Regex(#"^(.+)(_\d+of\d+)$");
foreach (var input in inputs)
{
var match = pattern.Match(input);
if (!match.Success)
{
// file doesn't end with "#of#", so use the whole input
Console.WriteLine(input);
}
else
{
// it does end with "#of#", so use the first capture group
Console.WriteLine(match.Groups[1].Value);
}
}
This code returns:
example_File
example_File2
examp_File
example
The Regex pattern has three parts:
^ and $ are anchors to ensure you capture the entire string, not just a subset of characters.
(.+) - match everything, be as greedy as possible.
(_\d+of\d+) - match "_#of#", where "#" can be any number of consecutive digits.

Best way to use Regex and int's

I have an application that loops through a group of documents and if a value is detected, then the user receives a prompt to replace this value. My current code looks like the following;
if (alllines[i].Contains("$"))
{
// prompt
int dollarIndex = alllines[i].IndexOf("%");
string nextTenChars = alllines[i].Substring(dollarIndex + 1, 18);
string PromtText = nextTenChars.Replace("%", "").Replace("/*", "").Replace("*/", "");
string promptValue = CreateInput.ShowDialog(PromtText, fi.FullName);
if (promptValue.Equals(""))
{
}
else
{
alllines[i] = alllines[i].Replace("$", promptValue);
File.WriteAllLines(fi.FullName, alllines.ToArray());
}
}
As you can see the prompt box displays 18 characters after the index which in this case is % however, if there are not 18 characters then the application crashes. What I want to do is use regex but I am unsure of how to apply this in the codes current state.
If I use the below I get the error Cannot convert from int to string any help would be appreciated.
Regex regex = new Regex(#"(\$.{1,10})");
var chars = regex.Matches(dollarIndex);

This should work
Regex regex = new Regex(#"(/*%.{1,50})");
var chars = regex.Match(alllines[i]).ToString();
string promptValue = CreateInput.ShowDialog(PromtText, fi.FullName);

Custom Uppercase on String

hi i was trying to make a program that modified a word in a string to a uppercase word.
the uppercase word is in a tag like this :
the <upcase>weather</upcase> is very <upcase>hot</upcase>
the result :
the WEATHER is very HOT
my code is like this :
string upKey = "<upcase>";
string lowKey = "</upcase>";
string quote = "the lazy <upcase>fox jump over</upcase> the dog <upcase> something here </upcase>";
int index = quote.IndexOf(upKey);
int indexEnd = quote.IndexOf(lowKey);
while(index!=-1)
{
for (int a = 0; a < index; a++)
{
Console.Write(quote[a]);
}
string upperQuote = "";
for (int b = index + 8; b < indexEnd; b++)
{
upperQuote += quote[b];
}
upperQuote = upperQuote.ToUpper().ToString();
Console.Write(upperQuote);
for (int c = indexEnd+9;c<quote.Length;c++)
{
if (quote[c]=='<')
{
break;
}
Console.Write(quote[c]);
}
index = quote.IndexOf(upKey, index + 1);
indexEnd = quote.IndexOf(lowKey, index + 1);
}
Console.WriteLine();
}
i have been trying using this code,and a while(while (indexEnd != -1)) :
index = quote.IndexOf(upKey, index + 1);
indexEnd = quote.IndexOf(lowKey, index + 1);
but that not work, the program run into unlimited loop, btw i'm a noob so please give a answer that i can understand :)

You can use a regular expression for this:
string input = "the <upcase>weather</upcase> is very <upcase>hot</upcase>";
var regex = new Regex("<upcase>(?<theMatch>.*?)</upcase>");
var result = regex.Replace(input, match => match.Groups["theMatch"].Value.ToUpper());
// result will be: "the WEATHER is very HOT"
Here's an explanation taken from here for the regular expression used above:
<upcase> matches the characters <upcase> literally (case sensitive)
(?<theMatch>.\*?) Named capturing group theMatch
.*? matches any character (except newline)
Quantifier: *? Between zero and unlimited times, as few times as possible, expanding as needed [lazy]
< matches the characters < literally
/ matches the character / literally
upcase> matches the characters upcase> literally (case sensitive)

The following will work as long as there are only matching tags and none of them are nested.
public static string Upper(string str)
{
const string start = "<upcase>";
const string end = "</upcase>";
var builder = new StringBuilder();
// Find the first start tag
int startIndex = str.IndexOf(start);
// If no start tag found then return the original
if (startIndex == -1)
return str;
// Append the part before the first tag as is
builder.Append(str.Substring(0, startIndex));
// Continue as long as we find another start tag.
while (startIndex != -1)
{
// Find the end tag for the current start tag
var endIndex = str.IndexOf(end, startIndex);
// Append the text between the start and end as upper case.
builder.Append(
str.Substring(
startIndex + start.Length,
endIndex - startIndex - start.Length).ToUpper());
// Find the next start tag.
startIndex = str.IndexOf(start, endIndex);
// Append the part after the end tag, but before the next start as is
builder.Append(
str.Substring(
endIndex + end.Length,
(startIndex == -1 ? str.Length : startIndex) - endIndex - end.Length));
}
return builder.ToString();
}

I'm not rewriting your code. Just answering your (main) question:
You need to keep a variable of the index you're at, and check for IndexOf from there only (See MSDN). Something like this:
int index = 0;
while (quote.IndexOf(upKey, index) != -1)
{
//Your code, including updating the value of index.
}
(I didn't check this on Visual Studio. This is just to point you in the direction that I think you're looking for.)
The reason for the infinite loop is that you're always testing IndexOf of the same index. Perhaps you mean to have quote.IndexOf(upKey, index += 1); which would change the value of index?

The way to go here is to probably use Regex but these easy parsing excercises are always fun to do manually. This can be easily solved using a very simple state machine.
What states can we have when dealing with strings of this nature? I can think of 4:
We are either parsing normal text
Or we are parsing an opening format tag '<...>'
Or we are parsing a closing format tag '</...>'
Or we are parsing text to be formatted between tags
I can't think of any other states. Now we need to think about the normal flow / transition between states. What should happen when we a parse string with the correct format?
Parser starts up expecting normal text. That is easy to understand.
If expecting normal text we encounter a '<' then the parser should switch to parsing opening format tag state. There is no other valid state transition.
If in parsing opening format tag state we encounter a '>' then the parser should switch to parsing text to be formatted. There is no other valid state transition.
If in parsing text to be formatted we encounter a '<' then the parser should switch to parsing closing tag. Again, there is no other valid state transition.
If in parsing closing tag we encounter a '>' then the parser should switch to normal text. Once more, there is no other valid transition. Note that we are disallowing nested tags.
Ok, so that seems pretty easy to understand. What do we need to implement this?
First we'll need something to represent the parsing states. A good old enum will do:
private enum ParsingState
{
UnformattedText,
OpenTag,
CloseTag,
FormattedText,
}
Now we need some string buffers to keep track of the final formatted string, the current format tag we are parsing and finally the substring we need to format. We will use several StringBuilder's for these as we don't know how long these buffers are and how many concatenations will be performed:
var formattedStringBuffer = new StringBuilder();
var formatBuffer = new StringBuilder();
var tagBuffer = new StringBuilder();
We will also need to keep track of the parser's state and the current active tag if any (so we can make sure that the parsed closing tag matches the current active tag):
var state = ParsingState.UnformattedText;
var activeFormatTag = string.Empty;
And now we are good to go, but before we do, can we generalize this so it works with any format tag?
Yes we can, we just need to tell the parser what to do for each supported tag. We can do this easily just passing a along a Dictionary that ties each tag with the action it should perform. We do this the following way:
var formatter = new Dictionary<string, Func<string, string>>();
formatter.Add("upcase", s => s.ToUpperInvariant());
formatter.Add("lcase", s => s.ToLowerInvariant());
Great! Now our implementation could be the following:
public static string Parse(this string str, Dictionary<string, Func<string,string>> formatter)
{
var formattedStringBuffer = new StringBuilder();
var formatBuffer = new StringBuilder();
var tagBuffer = new StringBuilder();
var state = ParsingState.UnformattedText;
var activeFormatTag = string.Empty;
foreach (var c in str)
{
switch (state)
{
case ParsingState.UnformattedText:
{
if (c != '<')
{
formattedStringBuffer.Append(c);
}
else
{
state = ParsingState.OpenTag;
}
break;
}
case ParsingState.OpenTag:
{
if (c != '>')
{
tagBuffer.Append(c);
}
else
{
state = ParsingState.FormattedText;
activeFormatTag = tagBuffer.ToString();
tagBuffer.Clear();
}
break;
}
case ParsingState.FormattedText:
{
if (c != '<')
{
formatBuffer.Append(c);
}
else
{
state = ParsingState.CloseTag;
}
break;
}
case ParsingState.CloseTag:
{
if (c!='>')
{
tagBuffer.Append(c);
}
else
{
var expectedTag = $"/{activeFormatTag}";
var tag = tagBuffer.ToString();
if (tag != expectedTag)
throw new FormatException($"Expected closing tag not found: <{expectedTag}>.");
if (formatter.ContainsKey(activeFormatTag))
{
var formatted = formatter[activeFormatTag](formatBuffer.ToString());
formattedStringBuffer.Append(formatted);
tagBuffer.Clear();
formatBuffer.Clear();
state = ParsingState.UnformattedText;
}
else
throw new FormatException($"Format tag <{activeFormatTag}> not recognized.");
}
break;
}
}
}
if (state != ParsingState.UnformattedText)
throw new FormatException($"Bad format in specified string '{str}'");
return formattedStringBuffer.ToString();
}
Is it the most elegant solution? No, Regex will do a much better job, but being a beginner I would not recommend you start solving these kind of problems that way, you'll learn a whole lot more solving them manualy. You'll have plenty of time to learn Regex later on.

Replacing characters in a string with another string

So what I am trying to do is as follows :
example of a string is A4PC
I am trying to replace for example any occurance of "A" with "[A4]" so I would get and similar any occurance of "4" with "[A4]"
"[A4][A4]PC"
I tried doing a normal Replace on the string but found out I got
"[A[A4]]PC"
string badWordAllVariants =
restriction.Value.Replace("A", "[A4]").Replace("4", "[A4]")
since I have two A's in a row causing an issue.
So I was thinking it would be better rather than the replace on the string I need to do it on a character per character basis and then build up a string again.
Is there anyway in Linq or so to do something like this ?

You don't need any LINQ here - String.Replace works just fine:
string input = "AAPC";
string result = input.Replace("A", "[A4]"); // "[A4][A4]PC"
UPDATE: For your updated requirements I suggest to use regular expression replace
string input = "A4PC";
var result = Regex.Replace(input, "A|4", "[A4]"); // "[A4][A4]PC"

This works well for me:
string x = "AAPC";
string replace = x.Replace("A", "[A4]");
EDIT:
Based on the updated question, the issue is the second replacement. In order to replace multiple strings you will want to do this sequentially:
var original = "AAPC";
// add arbitrary room to allow for more new characters
StringBuilder resultString = new StringBuilder(original.Length + 10);
foreach (char currentChar in original.ToCharArray())
{
if (currentChar == 'A') resultString.Append("[A4]");
else if (currentChar == '4') resultString.Append("[A4]");
else resultString.Append(currentChar);
}
string result = resultString.ToString();
You can run this routine with any replacements you want to make (in this case the letters 'A' and '4' and it should work. If you would want to replace strings the code would be similar in structure but you would need to "look ahead" and probably use a for loop. Hopefully this helps!
By the way - you want to use a string builder here and not strings because strings are static which means space gets allocated every time you loop. (Not good!)

I think this should do the trick
string str = "AA4PC";
string result = Regex.Replace(str, #"(?<Before>[^A4]?)(?<Value>A|4)(?<After>[^A4]?)", (m) =>
{
string before = m.Groups["Before"].Value;
string after = m.Groups["After"].Value;
string value = m.Groups["Value"].Value;
if (before != "[" || after != "]")
{
return "[A4]";
}
return m.ToString();
});
It is going to replace A and 4 that hasn't been replaced yet for [A4].

Regex to remove single-line SQL comments (--)

Question:
Can anybody give me a working regex expression (C#/VB.NET) that can remove single line comments from a SQL statement ?
I mean these comments:
-- This is a comment
not those
/* this is a comment */
because I already can handle the star comments.
I have a made a little parser that removes those comments when they are at the start of the line, but they can also be somewhere after code or worse, in a SQL-string 'hello --Test -- World'
Those comments should also be removed (except those in a SQL string of course - if possible).
Surprisingly I didn't got the regex working. I would have assumed the star comments to be more difficult, but actually, they aren't.
As per request, here my code to remove /**/-style comments
(In order to have it ignore SQL-Style strings, you have to subsitute strings with a uniqueidentifier (i used 4 concated), then apply the comment-removal, then apply string-backsubstitution.
static string RemoveCstyleComments(string strInput)
{
string strPattern = #"/[*][\w\d\s]+[*]/";
//strPattern = #"/\*.*?\*/"; // Doesn't work
//strPattern = "/\\*.*?\\*/"; // Doesn't work
//strPattern = #"/\*([^*]|[\r\n]|(\*+([^*/]|[\r\n])))*\*+/ "; // Doesn't work
//strPattern = #"/\*([^*]|[\r\n]|(\*+([^*/]|[\r\n])))*\*+/ "; // Doesn't work
// http://stackoverflow.com/questions/462843/improving-fixing-a-regex-for-c-style-block-comments
strPattern = #"/\*(?>(?:(?>[^*]+)|\*(?!/))*)\*/"; // Works !
string strOutput = System.Text.RegularExpressions.Regex.Replace(strInput, strPattern, string.Empty, System.Text.RegularExpressions.RegexOptions.Multiline);
Console.WriteLine(strOutput);
return strOutput;
} // End Function RemoveCstyleComments

I will disappoint all of you. This can't be done with regular expressions. Sure, it's easy to find comments not in a string (that even the OP could do), the real deal is comments in a string. There is a little hope of the look arounds, but that's still not enough. By telling that you have a preceding quote in a line won't guarantee anything. The only thing what guarantees you something is the oddity of quotes. Something you can't find with regular expression. So just simply go with non-regular-expression approach.
EDIT:
Here's the c# code:
String sql = "--this is a test\r\nselect stuff where substaff like '--this comment should stay' --this should be removed\r\n";
char[] quotes = { '\'', '"'};
int newCommentLiteral, lastCommentLiteral = 0;
while ((newCommentLiteral = sql.IndexOf("--", lastCommentLiteral)) != -1)
{
int countQuotes = sql.Substring(lastCommentLiteral, newCommentLiteral - lastCommentLiteral).Split(quotes).Length - 1;
if (countQuotes % 2 == 0) //this is a comment, since there's an even number of quotes preceding
{
int eol = sql.IndexOf("\r\n") + 2;
if (eol == -1)
eol = sql.Length; //no more newline, meaning end of the string
sql = sql.Remove(newCommentLiteral, eol - newCommentLiteral);
lastCommentLiteral = newCommentLiteral;
}
else //this is within a string, find string ending and moving to it
{
int singleQuote = sql.IndexOf("'", newCommentLiteral);
if (singleQuote == -1)
singleQuote = sql.Length;
int doubleQuote = sql.IndexOf('"', newCommentLiteral);
if (doubleQuote == -1)
doubleQuote = sql.Length;
lastCommentLiteral = Math.Min(singleQuote, doubleQuote) + 1;
//instead of finding the end of the string you could simply do += 2 but the program will become slightly slower
}
}
Console.WriteLine(sql);
What this does: find every comment literal. For each, check if it's within a comment or not, by counting the number of quotes between the current match and the last one. If this number is even, then it's a comment, thus remove it (find first end of line and remove whats between). If it's odd, this is within a string, find the end of the string and move to it. Rgis snippet is based on a wierd SQL trick: 'this" is a valid string. Even tho the 2 quotes differ. If it's not true for your SQL language, you should try a completely different approach. I'll write a program to that too if that's the case, but this one's faster and more straightforward.

You want something like this for the simple case
-{2,}.*
The -{2,} looks for a dash that happens 2 or more times
The .* gets the rest of the lines up to the newline
*But, for the edge cases, it appears that SinistraD is correct in that you cannot catch everything, however here is an article about how this can be done in C# with a combination of code and regex.

This seems to work well for me so far; it even ignores comments within strings, such as SELECT '--not a comment--' FROM ATable
private static string removeComments(string sql)
{
string pattern = #"(?<=^ ([^'""] |['][^']*['] |[""][^""]*[""])*) (--.*$|/\*(.|\n)*?\*/)";
return Regex.Replace(sql, pattern, "", RegexOptions.IgnorePatternWhitespace | RegexOptions.Multiline);
}
Note: it is designed to eliminate both /**/-style comments as well as -- style. Remove |/\*(.|\n)*?\*/ to get rid of the /**/ checking. Also be sure you are using the RegexOptions.IgnorePatternWhitespace Regex option!!
I wanted to be able to handle double-quotes too, but since T-SQL doesn't support them, you could get rid of |[""][^""]*[""] too.
Adapted from here.
Note (Mar 2015): In the end, I wound up using Antlr, a parser generator, for this project. There may have been some edge cases where the regex didn't work. In the end I was much more confident with the results having used Antlr, and it's worked well.

Using System.Text.RegularExpressions;
public static string RemoveSQLCommentCallback(Match SQLLineMatch)
{
System.Text.StringBuilder sb = new System.Text.StringBuilder();
bool open = false; //opening of SQL String found
char prev_ch = ' ';
foreach (char ch in SQLLineMatch.ToString())
{
if (ch == '\'')
{
open = !open;
}
else if ((!open && prev_ch == '-' && ch == '-'))
{
break;
}
sb.Append(ch);
prev_ch = ch;
}
return sb.ToString().Trim('-');
}
The code
public static void Main()
{
string sqlText = "WHERE DEPT_NAME LIKE '--Test--' AND START_DATE < SYSDATE -- Don't go over today";
//for every matching line call callback func
string result = Regex.Replace(sqlText, ".*--.*", RemoveSQLCommentCallback);
}
Let's replace, find all the lines that match dash dash comment and call your parsing function for every match.

As a late solution, the simplest way is to do it using ScriptDom-TSqlParser:
// https://michaeljswart.com/2014/04/removing-comments-from-sql/
// http://web.archive.org/web/*/https://michaeljswart.com/2014/04/removing-comments-from-sql/
public static string StripCommentsFromSQL(string SQL)
{
Microsoft.SqlServer.TransactSql.ScriptDom.TSql150Parser parser =
new Microsoft.SqlServer.TransactSql.ScriptDom.TSql150Parser(true);
System.Collections.Generic.IList<Microsoft.SqlServer.TransactSql.ScriptDom.ParseError> errors;
Microsoft.SqlServer.TransactSql.ScriptDom.TSqlFragment fragments =
parser.Parse(new System.IO.StringReader(SQL), out errors);
// clear comments
string result = string.Join(
string.Empty,
fragments.ScriptTokenStream
.Where(x => x.TokenType != Microsoft.SqlServer.TransactSql.ScriptDom.TSqlTokenType.MultilineComment)
.Where(x => x.TokenType != Microsoft.SqlServer.TransactSql.ScriptDom.TSqlTokenType.SingleLineComment)
.Select(x => x.Text));
return result;
}
or instead of using the Microsoft-Parser, you can use ANTL4 TSqlLexer
or without any parser at all:
private static System.Text.RegularExpressions.Regex everythingExceptNewLines =
new System.Text.RegularExpressions.Regex("[^\r\n]");
// http://drizin.io/Removing-comments-from-SQL-scripts/
// http://web.archive.org/web/*/http://drizin.io/Removing-comments-from-SQL-scripts/
public static string RemoveComments(string input, bool preservePositions, bool removeLiterals = false)
{
//based on http://stackoverflow.com/questions/3524317/regex-to-strip-line-comments-from-c-sharp/3524689#3524689
var lineComments = #"--(.*?)\r?\n";
var lineCommentsOnLastLine = #"--(.*?)$"; // because it's possible that there's no \r\n after the last line comment
// literals ('literals'), bracketedIdentifiers ([object]) and quotedIdentifiers ("object"), they follow the same structure:
// there's the start character, any consecutive pairs of closing characters are considered part of the literal/identifier, and then comes the closing character
var literals = #"('(('')|[^'])*')"; // 'John', 'O''malley''s', etc
var bracketedIdentifiers = #"\[((\]\])|[^\]])* \]"; // [object], [ % object]] ], etc
var quotedIdentifiers = #"(\""((\""\"")|[^""])*\"")"; // "object", "object[]", etc - when QUOTED_IDENTIFIER is set to ON, they are identifiers, else they are literals
//var blockComments = #"/\*(.*?)\*/"; //the original code was for C#, but Microsoft SQL allows a nested block comments // //https://msdn.microsoft.com/en-us/library/ms178623.aspx
//so we should use balancing groups // http://weblogs.asp.net/whaggard/377025
var nestedBlockComments = #"/\*
(?>
/\* (?<LEVEL>) # On opening push level
|
\*/ (?<-LEVEL>) # On closing pop level
|
(?! /\* | \*/ ) . # Match any char unless the opening and closing strings
)+ # /* or */ in the lookahead string
(?(LEVEL)(?!)) # If level exists then fail
\*/";
string noComments = System.Text.RegularExpressions.Regex.Replace(input,
nestedBlockComments + "|" + lineComments + "|" + lineCommentsOnLastLine + "|" + literals + "|" + bracketedIdentifiers + "|" + quotedIdentifiers,
me => {
if (me.Value.StartsWith("/*") && preservePositions)
return everythingExceptNewLines.Replace(me.Value, " "); // preserve positions and keep line-breaks // return new string(' ', me.Value.Length);
else if (me.Value.StartsWith("/*") && !preservePositions)
return "";
else if (me.Value.StartsWith("--") && preservePositions)
return everythingExceptNewLines.Replace(me.Value, " "); // preserve positions and keep line-breaks
else if (me.Value.StartsWith("--") && !preservePositions)
return everythingExceptNewLines.Replace(me.Value, ""); // preserve only line-breaks // Environment.NewLine;
else if (me.Value.StartsWith("[") || me.Value.StartsWith("\""))
return me.Value; // do not remove object identifiers ever
else if (!removeLiterals) // Keep the literal strings
return me.Value;
else if (removeLiterals && preservePositions) // remove literals, but preserving positions and line-breaks
{
var literalWithLineBreaks = everythingExceptNewLines.Replace(me.Value, " ");
return "'" + literalWithLineBreaks.Substring(1, literalWithLineBreaks.Length - 2) + "'";
}
else if (removeLiterals && !preservePositions) // wrap completely all literals
return "''";
else
throw new System.NotImplementedException();
},
System.Text.RegularExpressions.RegexOptions.Singleline | System.Text.RegularExpressions.RegexOptions.IgnorePatternWhitespace);
return noComments;
}

I don't know if C#/VB.net regex is special in some way but traditionally s/--.*// should work.

In PHP, i'm using this code to uncomment SQL (only single line):
$sqlComments = '#(([\'"`]).*?[^\\\]\2)|((?:\#|--).*?$)\s*|(?<=;)\s+#ms';
/* Commented version
$sqlComments = '#
(([\'"`]).*?[^\\\]\2) # $1 : Skip single & double quoted + backticked expressions
|((?:\#|--).*?$) # $3 : Match single line comments
\s* # Trim after comments
|(?<=;)\s+ # Trim after semi-colon
#msx';
*/
$uncommentedSQL = trim( preg_replace( $sqlComments, '$1', $sql ) );
preg_match_all( $sqlComments, $sql, $comments );
$extractedComments = array_filter( $comments[ 3 ] );
var_dump( $uncommentedSQL, $extractedComments );
To remove all comments see Regex to match MySQL comments