Property or indexer cannot be assigned to :: string2[i] = sting1[i]

Question

using System;

namespace stringdouble
{
    public class populate
    {
        public string string1;
        public string string2;

        public populate (string string1 ,string string2)
        {
            for (int i=1; i < string1.Length; i++)
            {
                if (string1[i] == string1[i-1])
                {
                    string2[i] = string1[i];//error on this line
                    Console.WriteLine ("Character Copied");
                    Console.ReadKey();
                    Console.Clear();
                }
            }

            Console.WriteLine (string2);
        }
    }

This is the code but for some reason its giving me the error I entered above. I am trying to remove the duplicates in a string and copy them into a new one.

I call this by new populate(FirstString, SecondString);.

Strings are immutable in `C#`. Create new string as a result instead. — BartoszKP, Oct 08 '13 at 10:20
those properties can not be changed like that they are read only — Vinay Pratap Singh Bhadauria, Oct 08 '13 at 10:22
Not related to what you ask, but why does the class have to public fields `string1;` and `string2;` that are not used, while the constructor `public populate (string string1 ,string string2)` takes in two arguments of the same names but never assign to the fields? — Jeppe Stig Nielsen, Oct 08 '13 at 11:04

Tim Schmelter · Accepted Answer · 2013-10-08T10:37:39.540

Strings are immutable, so once they are created you cannot modify them without creating a new string. That's why you get the exception when you try to modify a charcter from a string.

You could use Linq to get only unique characters:

string uniqueCharacters = new string(string1.Distinct().ToArray());

or, if you want all duplicate chars in a new string:

var dupChars = string1.GroupBy(c => c)
   .Where(g => g.Count() > 1)
   .Select(g => g.First());
string dupliateCharacters = new string(dupChars.ToArray());

As BartozKP has mentioned, maybe you want to create a string of equal adjacent characters. Here is a possible implementation using a StringBuilder and a loop:

public string Populate(string text)
{
    StringBuilder sb = new StringBuilder();
    if(text.Length > 1)
    {
        for (int i = 1; i < text.Length; i++)
        { 
            Char c = text[i];
            if (c == text[i - 1])
                sb.Append(c);
        }
    }
    return sb.ToString();
}

score 4 · Answer 2 · edited Oct 08 '13 at 10:27

4

You may convert your string into an array of characters using String#ToCharArray(). In your code:

char[] chars1 = string1.ToCharArray();
....
string result = new string(chars);

edited Oct 08 '13 at 10:27

BartoszKP

34,786
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answered Oct 08 '13 at 10:23

MakePeaceGreatAgain

35,491
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Using a `StringBuilder` also gives the ability to set separate `char` values by index, as in `myStringBuilder[7] = 'y';`, but it has lots of other nice string features as well, so he might prefer it over a simple `char[]` array. The array has many limitations, one being that it has a fixed length. – Jeppe Stig Nielsen Oct 08 '13 at 10:44

Sadique · Answer 3 · 2013-10-08T10:31:12.617

2

string is an alias for String in the .NET Framework. And .NET String is immutable. Make string2 an object of StringBuilder class to make your code work.

edited Oct 08 '13 at 10:31

answered Oct 08 '13 at 10:22

Sadique

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BartoszKP · Answer 4 · 2013-11-25T16:53:36.530

A working version which doesn't your actual functionality:

public class populate
{
    public populate (string string1 ,string string2)
    {
        char[] result = string2.ToCharArray();

        for (int i=1; i < string1.Length; i++)
        {
            if (string1[i] == string1[i-1])
            {
                result[i] = string1[i];
                Console.WriteLine ("Character Copied");
                Console.ReadKey();
                Console.Clear();
            }
        }

        string2 = new string(result);

        Console.WriteLine (string2);
    }

Based on answer provided by HimBromBeere. However this won't remove all duplicates from the string1. If you really want to do this, refer to TimSchmelter's answer.

Property or indexer cannot be assigned to :: string2[i] = sting1[i]

4 Answers4

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