using System.Linq;

using System.Diagnostics;

using System;

using System.Text;

using System.Globalization;

​

//Created for 

//http://metadataconsulting.blogspot.com/2019/03/A-Unicode-ReplaceAt-string-extension-method-handles-Unicode-string-properly.html

​

public static class Program

{

​

    const char cEMPTY = '\0'; 

    static readonly string EMPTY = cEMPTY.ToString(); 

    public static string UnicodeReplaceAt(this string str, int offset, char replaceChar)

    {

        int count = 1; //number of characters to remove at location offset

        string replaceBy = replaceChar.ToString();

        return new StringInfo(str).ReplaceByPosition(replaceBy, offset, count).String;

    }

​

    public static StringInfo ReplaceByPosition(this StringInfo str, string replaceBy, int offset, int count)

    {

        if (replaceBy != EMPTY)

            return str.RemoveByTextElements(offset, count).InsertByTextElements(offset, replaceBy);

        else if (!string.IsNullOrEmpty(replaceBy))

            return str.RemoveByTextElements(offset, count).InsertByTextElements(offset, replaceBy);

        else

            return str.RemoveByTextElements(offset, count);

    }

​

    public static StringInfo RemoveByTextElements(this StringInfo str, int offset, int count)

    { 

        //Tue 20-Aug-19 11:32am metadataconsulting.ca - replaceat index > string.len return orginal string

        if (offset > str.LengthInTextElements)

            return str;

        return new StringInfo(string.Concat(

            str.SubstringByTextElements(0, offset),

            offset + count < str.LengthInTextElements

                ? str.SubstringByTextElements(offset + count, str.LengthInTextElements - count - offset)

                : string.Empty

            ));

    }

    public static StringInfo InsertByTextElements(this StringInfo str, int offset, string insertStr)

    {

        //Tue 20-Aug-19 11:32am metadataconsulting.ca - replaceat index > string.len return orginal string

        if (offset > str.LengthInTextElements)

            return str;

        if (string.IsNullOrEmpty(str.String))

            return new StringInfo(insertStr);

​

        return new StringInfo(string.Concat(

            str.SubstringByTextElements(0, offset),

            insertStr,

            str.LengthInTextElements - offset > 0 ? str.SubstringByTextElements(offset, str.LengthInTextElements - offset) : ""

        ));

    }

​

    public static string SubsituteStringStringBuilder(this string s, int idx, char replaceChar)

    {

        if (string.IsNullOrEmpty(s) || idx >= s.Length || idx < 0)

            return s;

​

        return new StringBuilder(s).Remove(idx, 1).Insert(idx, replaceChar.ToString()).ToString();

    }

​

    public static string ReplaceAtSubstring(this string s, int idx, char replaceChar)

    {

        if (string.IsNullOrEmpty(s) || idx >= s.Length || idx < 0)

            return s;

​

        return s.Substring(0, idx) + replaceChar.ToString() + s.Substring(idx + replaceChar.ToString().Length, s.Length - (idx + replaceChar.ToString().Length));

​

    }

​

    public static string ReplaceAtStringManipulation(this string s, int idx, char replaceChar)

    {

        if (string.IsNullOrEmpty(s) || idx >= s.Length || idx < 0)

            return s;

​

        return s.Remove(idx, 1).Insert(idx, replaceChar.ToString());

    }

​

    public static string ReplaceAtLinq(this string value, int index, char newchar)

    {

        if (value.Length <= index)

            return value;

        else

            return string.Concat(value.Select((c, i) => i == index ? newchar : c));

    }

​

    public static string ReplaceAtCharArray(this string input, uint index, char newChar)

    {

        if (string.IsNullOrEmpty(input) || index >= input.Length)

            return input;

​

        char[] chars = input.ToCharArray();

        chars[index] = newChar;

        return new string(chars);

    }

​

    public static void Main()

    {

        //In .NET 4.5 and later also UTF-16 is supported

        //Console.OutputEncoding = System.Text.Encoding.Unicode;  

        //é  Latin Small Letter e with Acute U+00E9 - single byte Unicode character

        //😊 Smiling Face with Smiling Eyes Emoji U+1F60A - double byte Unicode character

        //🎶 Multiple Musical Notes Emoji U+1F3B6 - - double byte Unicode character

        //🔥 Fire Emoji U+1F525 -- double byte Unicode character

        Console.WriteLine("Unicode String Replace At Issue");

        Console.WriteLine("Lets examine string \"🎶🔥é-\"");  

        Console.WriteLine("🎶🔥é- is length of " + "🎶🔥é-".Length + ", but there are ONLY 4 characters! Why not len=4?"); 

        Console.WriteLine("🎶🔥 are double byte UNICODE characters (> \\u10000) of width or len 2 each ");

        Console.WriteLine("🎶🔥é- below will replace space after lasting character '-' (position 4) with a sub using most common techniques seen online"); 

        Console.WriteLine(); 

        Stopwatch sw = new Stopwatch();

        sw.Start();

        Console.WriteLine("🎶🔥é- using ReplaceAtCharArray".ReplaceAtCharArray(4, 'X'));

        sw.Stop();

        Console.WriteLine("in {0} ticks.", sw.ElapsedTicks.ToString("N0"));

​

        sw.Restart();

        Console.WriteLine("🎶🔥é- using ReplaceAtLinq".ReplaceAtLinq(4, 'Y'));

        sw.Stop();

        Console.WriteLine("in {0} ticks.", sw.ElapsedTicks.ToString("N0"));

​

        sw.Restart();

        Console.WriteLine("🎶🔥é- using ReplaceAtStringManipulation".ReplaceAtStringManipulation(4, 'Z'));

        sw.Stop();

        Console.WriteLine("in {0} ticks.", sw.ElapsedTicks.ToString("N0"));

​

        sw.Restart();

        Console.WriteLine("🎶🔥é- using ReplaceAtSubstring".ReplaceAtSubstring(4, 'A'));

        sw.Stop();

        Console.WriteLine("in {0} ticks.", sw.ElapsedTicks.ToString("N0"));

​

        sw.Restart();

        Console.WriteLine("🎶🔥é- using SubsituteStringStringBuilder".SubsituteStringStringBuilder(4, 'W'));

        sw.Stop();

        Console.WriteLine("in {0} ticks.", sw.ElapsedTicks.ToString("N0"));

​

        sw.Restart();

        Console.WriteLine("🎶🔥é- using UnicodeReplaceAt".UnicodeReplaceAt(4, '4'));

        sw.Stop();

        Console.WriteLine("in {0} ticks.", sw.ElapsedTicks.ToString("N0"));

        Console.WriteLine(); 

        Console.WriteLine("UnicodeReplaceAt replaces properly at position 4 in zero based index string");

        Console.WriteLine(); 

        sw.Restart();

        Console.Write("🎶🔥é- using UnicodeReplaceAt(0, '0')".UnicodeReplaceAt(0, '0'));

        sw.Stop();

        Console.WriteLine(" in {0} ticks.", sw.ElapsedTicks.ToString("N0"));

        sw.Restart();

        Console.Write("🎶🔥é- using UnicodeReplaceAt(1, '1')".UnicodeReplaceAt(1, '1'));

        sw.Stop();

        Console.WriteLine(" in {0} ticks.", sw.ElapsedTicks.ToString("N0"));

        sw.Restart();

        Console.Write("🎶🔥é- using UnicodeReplaceAt(2, '2')".UnicodeReplaceAt(2, '2'));

        sw.Stop();

        Console.WriteLine(" in {0} ticks.", sw.ElapsedTicks.ToString("N0"));

        sw.Restart();

        Console.Write("🎶🔥é- using UnicodeReplaceAt(3, '3')".UnicodeReplaceAt(3, '3'));

        sw.Stop();

        Console.WriteLine(" in {0} ticks.", sw.ElapsedTicks.ToString("N0"));

        sw.Restart();

        Console.Write("🎶🔥é- using UnicodeReplaceAt(4, '4')".UnicodeReplaceAt(4, '4'));

        sw.Stop();

        Console.WriteLine(" in {0} ticks.", sw.ElapsedTicks.ToString("N0"));

        Console.Write("🎶🔥é-".UnicodeReplaceAt(5, '5')+" using UnicodeReplaceAt(5, '5') - this is beyond end of string, so return orginal string");

        sw.Stop();

        Console.WriteLine(" in {0} ticks.", sw.ElapsedTicks.ToString("N0"));

        Console.WriteLine(); 

        Console.WriteLine("String.Replace works, but replaces all characters, not at specific location as above functions");

        Console.WriteLine(); 

        Console.Write("🎶🔥é- using String.Replace".Replace("🔥", "+") + "('🔥', '+')");

​

    }

}