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Search text file for text above which pattern matches input

I am trying to make my program display the text above the input text which matches a pattern I set.
For example, if user input 'FastModeIdleImmediateCount"=dword:00000000', I should get the closest HKEY above, which is [HKEY_CURRENT_CONFIG\System\CurrentControlSet\Enum\SCSI\Disk&Ven_ATA&Prod_TOSHIBA_MQ01ABD0\4&6a0976b&0&000000] for this case.
[HKEY_CURRENT_CONFIG\System\CurrentControlSet\Enum\SCSI\Disk&Ven_ATA&Prod_TOSHIBA_MQ01ABD0\4&6a0976b&0&000000]
"StandardModeIdleImmediateCount"=dword:00000000
"FastModeIdleImmediateCount"=dword:00000000
[HKEY_CURRENT_CONFIG\System\CurrentControlSet\SERVICES]
[HKEY_CURRENT_CONFIG\System\CurrentControlSet\SERVICES\TSDDD]
[HKEY_CURRENT_CONFIG\System\CurrentControlSet\SERVICES\TSDDD\DEVICE0]
"Attach.ToDesktop"=dword:00000001
Could anyone please show me how I can code something like that? I tried playing around with regular expressions to match text with bracket, but I am not sure how to make it to only search for the text above my input.

I'm assuming your file is a .txt file, although it's most probably not. But the logic is the same.
It is not hard at all, a simple for() loop would do the trick.
Code with the needed description:
string[] lines = File.ReadAllLines(#"d:\test.txt");//replace your directory. We're getting all lines from a text file.
string inputToSearchFor = "\"FastModeIdleImmediateCount\"=dword:00000000"; //that's the string to search for
int indexOfMatchingLine = Array.FindIndex(lines, line => line == inputToSearchFor); //getting the index of the line, which equals the matchcode
string nearestHotKey = String.Empty;
for(int i = indexOfMatchingLine; i >=0; i--) //looping for lines above the matched one to find the hotkey
{
if(lines[i].IndexOf("[HKEY_") == 0) //if we find a line which begins with "[HKEY_" (that means it's a hotkey, right?)
{
nearestHotKey = lines[i]; //we get the line into our hotkey string
break; //breaking the loop
}
}
if(nearestHotKey != String.Empty) //we have actually found a hotkey, so our string is not empty
{
//add code...
}

You could try to split the text into lines, find the index of the line that contains your text (whether exact match or regex is used doesn't matter) and then backsearch for the first key. Reverse sorting the lines first might help.

how to find indexof substring in a text file

I have converted an asp.net c# project to framework 3.5 using VS 2008. Purpose of app is to parse a text file containing many rows of like information then inserting the data into a database.
I didn't write original app but developer used substring() to fetch individual fields because they always begin at the same position.
My question is:
What is best way to find the index of substring in text file without having to manually count the position? Does someone have preferred method they use to find position of characters in a text file?

I would say IndexOf() / IndexOfAny() together with Substring(). Alternatively, regular expressions. It the file has an XML-like structure, this.

If the files are delimited eg with commas you can use string.Split
If data is: string[] text = { "1, apple", "2, orange", "3, lemon" };
private void button1_Click(object sender, EventArgs e)
{
string[] lines = this.textBoxIn.Lines;
List<Fruit> fields = new List<Fruit>();
foreach(string s in lines)
{
char[] delim = {','};
string[] fruitData = s.Split(delim);
Fruit f = new Fruit();
int tmpid = 0;
Int32.TryParse(fruitData[0], out tmpid);
f.id = tmpid;
f.name = fruitData[1];
fields.Add(f);
}
this.textBoxOut.Clear();
string text=string.Empty;
foreach(Fruit item in fields)
{
text += item.ToString() + " \n";
}
this.textBoxOut.Text = text;
}
}

The text file I'm reading does not contain delimiters - sometimes there spaces between fields and sometimes they run together. In either case, every line is formatted the same. When I asked the question I was looking at the file in notepad.
Question was: how do you find the position in a file so that position (a number) could be specified as the startIndex of my substring function?
Answer: I've found that opening the text file in notepad++ will display the column # and line count of any position where the curser is in the file and makes this job easier.

You can use indexOf() and then use Length() as the second substring parameter
substr = str.substring(str.IndexOf("."), str.Length - str.IndexOf("."));

Extracting values from a string in C#

I have the following string which i would like to retrieve some values from:
============================
Control 127232:
map #;-
============================
Control 127235:
map $;NULL
============================
Control 127236:
I want to take only the Control . Hence is there a way to retrieve from that string above into an array containing like [127232, 127235, 127236]?

One way of achieving this is with regular expressions, which does introduce some complexity but will give the answer you want with a little LINQ for good measure.
Start with a regular expression to capture, within a group, the data you want:
var regex = new Regex(#"Control\s+(\d+):");
This will look for the literal string "Control" followed by one or more whitespace characters, followed by one or more numbers (within a capture group) followed by a literal string ":".
Then capture matches from your input using the regular expression defined above:
var matches = regex.Matches(inputString);
Then, using a bit of LINQ you can turn this to an array
var arr = matches.OfType<Match>()
.Select(m => long.Parse(m.Groups[1].Value))
.ToArray();
now arr is an array of long's containing just the numbers.
Live example here: http://rextester.com/rundotnet?code=ZCMH97137

try this (assuming your string is named s and each line is made with \n):
List<string> ret = new List<string>();
foreach (string t in s.Split('\n').Where(p => p.StartsWith("Control")))
ret.Add(t.Replace("Control ", "").Replace(":", ""));
ret.Add(...) part is not elegant, but works...
EDITED:
If you want an array use string[] arr = ret.ToArray();
SYNOPSYS:
I see you're really a newbie, so I try to explain:
s.Split('\n') creates a string[] (every line in your string)
.Where(...) part extracts from the array only strings starting with Control
foreach part navigates through returned array taking one string at a time
t.Replace(..) cuts unwanted string out
ret.Add(...) finally adds searched items into returning list

Off the top of my head try this (it's quick and dirty), assuming the text you want to search is in the variable 'text':
List<string> numbers = System.Text.RegularExpressions.Regex.Split(text, "[^\\d+]").ToList();
numbers.RemoveAll(item => item == "");
The first line splits out all the numbers into separate items in a list, it also splits out lots of empty strings, the second line removes the empty strings leaving you with a list of the three numbers. if you want to convert that back to an array just add the following line to the end:
var numberArray = numbers.ToArray();

Yes, the way exists. I can't recall a simple way for It, but string is to be parsed for extracting this values. Algorithm of it is next:
Find a word "Control" in string and its end
Find a group of digits after the word
Extract number by int.parse or TryParse
If not the end of the string - goto to step one
realizing of this algorithm is almost primitive..)
This is simplest implementation (your string is str):
int i, number, index = 0;
while ((index = str.IndexOf(':', index)) != -1)
{
i = index - 1;
while (i >= 0 && char.IsDigit(str[i])) i--;
if (++i < index)
{
number = int.Parse(str.Substring(i, index - i));
Console.WriteLine("Number: " + number);
}
index ++;
}
Using LINQ for such a little operation is doubtful.

Extract File extensions using regular expression in C#

I wanna write a regular expression that can extract file types from a string.
the string is like:
Text Files
(.prn;.txt;.rtf;.csv;.wq1)|.prn;.txt;.rtf;.csv;.wq1|PDF
Files (.pdf)|.pdf|Excel Files
(.xls;.xlsx;.xlsm;.xlsb;.xlam;.xltx;.xltm;.xlw)
result e.g.
.prn

You have the dialog filterformat.
The extensions already appear twice (first appearance is unreliable) and when you try to handle this with a RegEx directly you'll have to think about
Text.Files (.prn;.txt;.rtf;.csv;.wq1)|.prn;.txt;.rtf;.csv;.wq1|
etc.
It looks safer to follow the known structure:
string filter = "Text Files (.prn;.txt;.rtf;.csv;.wq1)|.prn;.txt;.rtf;.csv;.wq1|PDF Files (.pdf)|.pdf|Excel Files (.xls;.xlsx;.xlsm;.xlsb;.xlam;.xltx;.xltm;.xlw)";
string[] filterParts = filter.Split("|");
// go through the odd sections
for (int i = 1; i < filterParts.Length; i += 2)
{
// approx, you may want some validation here first
string filterPart = filterParts[i];
string[] fileTypes = filterPart.Split(";");
// add to collection
}
This (only) requires that the filter string has the correct syntax.

Regex extensionRegex = new Regex(#"\.\w+");
foreach(Match m in extensionRegex.Matches(text))
{
Console.WriteLine(m.Value);
}

If that string format you have there is fairly fixed, then the following should work:
\.[^.;)]+

Find and Replace a section of a string with wildcard type search

I want to be able to read a file, and replace all instances of:
M9S1800.2 with S1800 (I want to get rid of the M9 and the .2).
The problem I am having is that the 4 digit number after the "S" can be different every time, as well as the number after the decimal.
For example,
It can be: M9S3200.1 or M9S5400.1 or M9S5400.2
Can someone please show me how to do this with C#?
I know how to find and replace by using this code:
StreamReader reader = new StreamReader(fDialog.FileName.ToString());
string content = reader.ReadToEnd();
reader.Close();
content = Regex.Replace(content, "M2", "M3");
but with the M9S3200.1, I want to do a wildcard type replace. For example it would be like replace M9S*.1 with S* so M9S3200.1 would just become S3200.

content = Regex.Replace(content, #"M9(S\d{4})\.\d", "$1");