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How to replace variable in user input with math operation?

I need replace variable in string from user. For example:
User input: Ssad asdsdqwdq jdiqwj diqw jd qwld j {price-40%} asd asd asd
I know how replace only {price} but I don't know how to replace other cases.
I need support these cases:
{price}
{price-xx%}
{price+xx%}
{price-xx}
{price+xx}
{price/xx}
{price*xx}
And user can use variable {price} many times.
After user submit text, my app replace variable {price} or calc {price-xx%} and create a new string.

If I understood your problem correctly then I think you can evaluate the whole expression without Replacing variables (might you have to change placements of variables)
First, add 'System.Data' name space in your project
then:
double price = 110;
double xx = 15;
double result = 0;
result = Convert.ToDouble(new DataTable().Compute($"({price-(price*xx)/100})", null));
Console.WriteLine("{price - xx%} = " + result);
result = Convert.ToDouble(new DataTable().Compute($"({price + (price * xx) / 100})", null));
Console.WriteLine("{price + xx%} = " + result);
result = Convert.ToDouble(new DataTable().Compute($"({price}-{xx})", null));
Console.WriteLine("{price - xx} = " + result);
result = Convert.ToDouble(new DataTable().Compute($"({price}+{xx})", null));
Console.WriteLine("{price + xx} = " + result);
result = Convert.ToDouble(new DataTable().Compute($"({price}/{xx})", null));
Console.WriteLine("{price / xx} = " + result);
result = Convert.ToDouble(new DataTable().Compute($"({price}*{xx})", null));
Console.WriteLine("{price * xx} = " + result);

https://github.com/davideicardi/DynamicExpresso/
static void Main(string[] args)
{
int price = 100;
Regex regex = new Regex(#"(?<=\{).*?(?=\})");
string userInput = "Hi. I want to buy your computer. I can't offer {price} USD, but I can offer {price-(price/100)*10} USD";
string text = userInput;
foreach (var item in regex.Matches(text))
{
string expression = item.ToString().Replace("price", price.ToString());
var interpreter = new Interpreter();
var result = interpreter.Eval(expression);
text = regex.Replace(text, result.ToString(),1);
text = ReplaceFirst(text, "{", string.Empty);
text = ReplaceFirst(text, "}", string.Empty);
}
Console.WriteLine("Result: " + text);
}
public static string ReplaceFirst(string text, string search, string replace)
{
int pos = text.IndexOf(search);
if (pos < 0)
{
return text;
}
return text.Substring(0, pos) + replace + text.Substring(pos + search.Length);
}

how to get the last items in a row

I have string like Joe Doe Doe , owner business
and I need to take from this string last name, first name, father name and his position.
var str = orgRequ.ValueName.Replace(",", "").Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
string LastName = str.Length > 0 ? str[0] : "";
string Name = str.Length > 1 ? str[1] : "";
string FatherName = str.Length > 2 ? str[2] : "";
string Positions=string.Join(" ", str.Reverse().Take(str.Count() - 3).ToArray());
but ran into a problem that the final position is written as System.Linq.Enumerable + d__75`1 [System.Char] instead of the owner business. before insert into the database, i need again reverse Positions , how can this be cleaned using best practices

Because you are reversing the str in string Positions you get Business Owner instead of Owner Business.
So either you take str[3] + str[4] for a result of Owner Business:
string Positions = str[3] + " " + str[4];
Or with your code, you have to reverse the two words (attention, quick and dirty):
string Positions = string.Join(" ", str.Reverse().Take(str.Count() - 3).ToArray());
string output = "";
string[] splitStrings = Positions.Split(' ');
for (int i = splitStrings.Length - 1; i > -1; i--)
{
output = output + splitStrings[i] + " ";
}
Console.WriteLine("Result: " + output); //Owner Business

C# Getting the text between 2 characters in a string

public String GetDirectory(String Path)
{
Console.WriteLine("Directorul: ");
var start = Path.IndexOf(":") + 6;
var match2 = Path.Substring(start, Path.IndexOf(".") - start);
return Path;
}
I need to get the path string between the 2 characters in this string:
"C:\Documents\Text.txt"
I want it to show the text between ':' and '.' at the end so :"\Documents\Text"

int start_index = Path.IndexOf(':')+1;
int end_index = Path.LastIndexOf('.');
int length = end_index-start_index;
string directory = Path.Substring(start_index,length);

Linq is always fascinating:
string s = string.Join("",
Path.SkipWhile(p => p != ':')
.Skip(1)
.TakeWhile(p => p != '.')
);

You can use string operations, but you can also use the System.IO.Path functions for a - in my personal opinion - more elegant solution:
string path = #"C:\Documents\Text.txt";
string pathRoot = Path.GetPathRoot(path); // pathRoot will be "C:\", for example
string result = Path.GetDirectoryName(path).Substring(pathRoot.Length - 1) +
Path.DirectorySeparatorChar +
Path.GetFileNameWithoutExtension(path);
Console.WriteLine(result);

you should return your match2 instead of the path since path will remain C:\Documents\Text.txt
public String GetDirectory(String Path)
{
Console.WriteLine("Directorul: ");
var start = Path.IndexOf(":") + 6;
var match2 = Path.Substring(start, Path.IndexOf(".") - start);
return match2;
}

patch = patch.Substring(patch.IndexOf(':') + 1, patch.IndexOf('.') - 2);

C# How can I compare two word strings and indicate which parts are different

For example if I have...
string a = "personil";
string b = "personal";
I would like to get...
string c = "person[i]l";
However it is not necessarily a single character. I could be like this too...
string a = "disfuncshunal";
string b = "dysfunctional";
For this case I would want to get...
string c = "d[isfuncshu]nal";
Another example would be... (Notice that the length of both words are different.)
string a = "parralele";
string b = "parallel";
string c = "par[ralele]";
Another example would be...
string a = "ato";
string b = "auto";
string c = "a[]to";
How would I go about doing this?
Edit: The length of the two strings can be different.
Edit: Added additional examples. Credit goes to user Nenad for asking.

I must be very bored today, but I actually made UnitTest that pass all 4 cases (if you did not add some more in the meantime).
Edit: Added 2 edge cases and fix for them.
Edit2: letters that repeat multiple times (and error on those letters)
[Test]
[TestCase("parralele", "parallel", "par[ralele]")]
[TestCase("personil", "personal", "person[i]l")]
[TestCase("disfuncshunal", "dysfunctional", "d[isfuncshu]nal")]
[TestCase("ato", "auto", "a[]to")]
[TestCase("inactioned", "inaction", "inaction[ed]")]
[TestCase("refraction", "fraction", "[re]fraction")]
[TestCase("adiction", "ad[]diction", "ad[]iction")]
public void CompareStringsTest(string attempted, string correct, string expectedResult)
{
int first = -1, last = -1;
string result = null;
int shorterLength = (attempted.Length < correct.Length ? attempted.Length : correct.Length);
// First - [
for (int i = 0; i < shorterLength; i++)
{
if (correct[i] != attempted[i])
{
first = i;
break;
}
}
// Last - ]
var a = correct.Reverse().ToArray();
var b = attempted.Reverse().ToArray();
for (int i = 0; i < shorterLength; i++)
{
if (a[i] != b[i])
{
last = i;
break;
}
}
if (first == -1 && last == -1)
result = attempted;
else
{
var sb = new StringBuilder();
if (first == -1)
first = shorterLength;
if (last == -1)
last = shorterLength;
// If same letter repeats multiple times (ex: addition)
// and error is on that letter, we have to trim trail.
if (first + last > shorterLength)
last = shorterLength - first;
if (first > 0)
sb.Append(attempted.Substring(0, first));
sb.Append("[");
if (last > -1 && last + first < attempted.Length)
sb.Append(attempted.Substring(first, attempted.Length - last - first));
sb.Append("]");
if (last > 0)
sb.Append(attempted.Substring(attempted.Length - last, last));
result = sb.ToString();
}
Assert.AreEqual(expectedResult, result);
}

Have you tried my DiffLib?
With that library, and the following code (running in LINQPad):
void Main()
{
string a = "disfuncshunal";
string b = "dysfunctional";
var diff = new Diff<char>(a, b);
var result = new StringBuilder();
int index1 = 0;
int index2 = 0;
foreach (var part in diff)
{
if (part.Equal)
result.Append(a.Substring(index1, part.Length1));
else
result.Append("[" + a.Substring(index1, part.Length1) + "]");
index1 += part.Length1;
index2 += part.Length2;
}
result.ToString().Dump();
}
You get this output:
d[i]sfunc[shu]nal
To be honest I don't understand what this gives you, as you seem to completely ignore the changed parts in the b string, only dumping the relevant portions of the a string.

Here is a complete and working console application that will work for both examples you gave:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApplication2
{
class Program
{
static void Main(string[] args)
{
string a = "disfuncshunal";
string b = "dysfunctional";
StringBuilder sb = new StringBuilder();
for (int i = 0; i < a.Length; i++)
{
if (a[i] != b[i])
{
sb.Append("[");
sb.Append(a[i]);
sb.Append("]");
continue;
}
sb.Append(a[i]);
}
var str = sb.ToString();
var startIndex = str.IndexOf("[");
var endIndex = str.LastIndexOf("]");
var start = str.Substring(0, startIndex + 1);
var mid = str.Substring(startIndex + 1, endIndex - 1);
var end = str.Substring(endIndex);
Console.WriteLine(start + mid.Replace("[", "").Replace("]", "") + end);
}
}
}
it will not work if you want to display more than one entire section of the mismatched word.

You did not specify what to do if the strings were of different lengths, but here is a solution to the problem when the strings are of equal length:
private string Compare(string string1, string string2) {
//This only works if the two strings are the same length..
string output = "";
bool mismatch = false;
for (int i = 0; i < string1.Length; i++) {
char c1 = string1[i];
char c2 = string2[i];
if (c1 == c2) {
if (mismatch) {
output += "]" + c1;
mismatch = false;
} else {
output += c1;
}
} else {
if (mismatch) {
output += c1;
} else {
output += "[" + c1;
mismatch = true;
}
}
}
return output;
}

Not really good approach but as an exercise in using LINQ: task seem to be find matching prefix and suffix for 2 strings, return "prefix + [+ middle of first string + suffix.
So you can match prefix (Zip + TakeWhile(a==b)), than repeat the same for suffix by reversing both strings and reversing result.
var first = "disfuncshunal";
var second = "dysfunctional";
// Prefix
var zipped = first.ToCharArray().Zip(second.ToCharArray(), (f,s)=> new {f,s});
var prefix = string.Join("",
zipped.TakeWhile(c => c.f==c.s).Select(c => c.f));
// Suffix
var zippedReverse = first.ToCharArray().Reverse()
.Zip(second.ToCharArray().Reverse(), (f,s)=> new {f,s});
var suffix = string.Join("",
zippedReverse.TakeWhile(c => c.f==c.s).Reverse().Select(c => c.f));
// Cut and combine.
var middle = first.Substring(prefix.Length,
first.Length - prefix.Length - suffix.Length);
var result = prefix + "[" + middle + "]" + suffix;
Much easier and faster approach is to use 2 for loops (from start to end, and from end to start).

Find a string between 2 known values

I need to be able to extract a string between 2 tags for example: "00002" from "morenonxmldata<tag1>0002</tag1>morenonxmldata"
I am using C# and .NET 3.5.

Regex regex = new Regex("<tag1>(.*)</tag1>");
var v = regex.Match("morenonxmldata<tag1>0002</tag1>morenonxmldata");
string s = v.Groups[1].ToString();
Or (as mentioned in the comments) to match the minimal subset:
Regex regex = new Regex("<tag1>(.*?)</tag1>");
Regex class is in System.Text.RegularExpressions namespace.

Solution without need of regular expression:
string ExtractString(string s, string tag) {
// You should check for errors in real-world code, omitted for brevity
var startTag = "<" + tag + ">";
int startIndex = s.IndexOf(startTag) + startTag.Length;
int endIndex = s.IndexOf("</" + tag + ">", startIndex);
return s.Substring(startIndex, endIndex - startIndex);
}

A Regex approach using lazy match and back-reference:
foreach (Match match in Regex.Matches(
"morenonxmldata<tag1>0002</tag1>morenonxmldata<tag2>abc</tag2>asd",
#"<([^>]+)>(.*?)</\1>"))
{
Console.WriteLine("{0}={1}",
match.Groups[1].Value,
match.Groups[2].Value);
}

Extracting contents between two known values can be useful for later as well. So why not create an extension method for it. Here is what i do, Short and simple...
public static string GetBetween(this string content, string startString, string endString)
{
int Start=0, End=0;
if (content.Contains(startString) && content.Contains(endString))
{
Start = content.IndexOf(startString, 0) + startString.Length;
End = content.IndexOf(endString, Start);
return content.Substring(Start, End - Start);
}
else
return string.Empty;
}

string input = "Exemple of value between two string FirstString text I want to keep SecondString end of my string";
var match = Regex.Match(input, #"FirstString (.+?) SecondString ").Groups[1].Value;

To get Single/Multiple values without regular expression
// For Single
var value = inputString.Split("<tag1>", "</tag1>")[1];
// For Multiple
var values = inputString.Split("<tag1>", "</tag1>").Where((_, index) => index % 2 != 0);

For future reference, I found this code snippet at http://www.mycsharpcorner.com/Post.aspx?postID=15 If you need to search for different "tags" it works very well.
public static string[] GetStringInBetween(string strBegin,
string strEnd, string strSource,
bool includeBegin, bool includeEnd)
{
string[] result ={ "", "" };
int iIndexOfBegin = strSource.IndexOf(strBegin);
if (iIndexOfBegin != -1)
{
// include the Begin string if desired
if (includeBegin)
iIndexOfBegin -= strBegin.Length;
strSource = strSource.Substring(iIndexOfBegin
+ strBegin.Length);
int iEnd = strSource.IndexOf(strEnd);
if (iEnd != -1)
{
// include the End string if desired
if (includeEnd)
iEnd += strEnd.Length;
result[0] = strSource.Substring(0, iEnd);
// advance beyond this segment
if (iEnd + strEnd.Length < strSource.Length)
result[1] = strSource.Substring(iEnd
+ strEnd.Length);
}
}
else
// stay where we are
result[1] = strSource;
return result;
}

I strip before and after data.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Text.RegularExpressions;
namespace testApp
{
class Program
{
static void Main(string[] args)
{
string tempString = "morenonxmldata<tag1>0002</tag1>morenonxmldata";
tempString = Regex.Replace(tempString, "[\\s\\S]*<tag1>", "");//removes all leading data
tempString = Regex.Replace(tempString, "</tag1>[\\s\\S]*", "");//removes all trailing data
Console.WriteLine(tempString);
Console.ReadLine();
}
}
}

Without RegEx, with some must-have value checking
public static string ExtractString(string soapMessage, string tag)
{
if (string.IsNullOrEmpty(soapMessage))
return soapMessage;
var startTag = "<" + tag + ">";
int startIndex = soapMessage.IndexOf(startTag);
startIndex = startIndex == -1 ? 0 : startIndex + startTag.Length;
int endIndex = soapMessage.IndexOf("</" + tag + ">", startIndex);
endIndex = endIndex > soapMessage.Length || endIndex == -1 ? soapMessage.Length : endIndex;
return soapMessage.Substring(startIndex, endIndex - startIndex);
}

public string between2finer(string line, string delimiterFirst, string delimiterLast)
{
string[] splitterFirst = new string[] { delimiterFirst };
string[] splitterLast = new string[] { delimiterLast };
string[] splitRes;
string buildBuffer;
splitRes = line.Split(splitterFirst, 100000, System.StringSplitOptions.RemoveEmptyEntries);
buildBuffer = splitRes[1];
splitRes = buildBuffer.Split(splitterLast, 100000, System.StringSplitOptions.RemoveEmptyEntries);
return splitRes[0];
}
private void button1_Click(object sender, EventArgs e)
{
string manyLines = "Received: from exim by isp2.ihc.ru with local (Exim 4.77) \nX-Failed-Recipients: rmnokixm#gmail.com\nFrom: Mail Delivery System <Mailer-Daemon#isp2.ihc.ru>";
MessageBox.Show(between2finer(manyLines, "X-Failed-Recipients: ", "\n"));
}