List emailAddress how to replace value in a particular string

Question

I have the following method

/// <summary>
    /// Replaces SemiColons with commas because SMTP client does not accept semi colons
    /// </summary>
    /// <param name="emailAddresses"></param>
    public static List<string> ReplaceSemiColon(List<string> emailAddresses) // Note only one string in the list...
    {         
        foreach (string email in emailAddresses)
        {
            email.Replace(";", ",");
        }

        //emailAddresses.Select(x => x.Replace(";", ","));  // Not working either


        return emailAddresses;
    }

However the email string is not replacing the ";" with the ",". What am I missing?

score 4 · Accepted Answer · answered Sep 27 '13 at 14:19

4

I think you should try setting it back to itself email = email.Replace(";", ",");

answered Sep 27 '13 at 14:19

Ryan Schlueter

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score 4 · Answer 2 · edited May 23 '17 at 12:14

4

String.Replace method returns new string. It doesn't change existing one.

Returns a new string in which all occurrences of a specified Unicode character or String in the current string are replaced with another specified Unicode character or String.

As Habib mentioned, using foreach with the current list gets a foreach iteration variable error. It is a read-only iteration. Create a new list and then add replaced values to it instead.

Also you can use for loop for modifying existing list which keyboardP explained on his answer.

List<string> newemailAddresses = new List<string>();
foreach (string email in emailAddresses)
{         
     newemailAddresses.Add(email.Replace(";", ","));
}
return newemailAddresses;

Be aware since strings are immutable types, you can't change them. Even if you think you change them, you actually create new strings object.

edited May 23 '17 at 12:14

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answered Sep 27 '13 at 14:19

Soner Gönül

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Soner, you can't modify iteration variable in foreach `Cannot assign to 'email' because it is a 'foreach iteration variable'` – Habib Sep 27 '13 at 14:26
@Habib Arrrhghhhh! Fool me `:)` Updated. I think it is ok now. – Soner Gönül Sep 27 '13 at 14:32
it looks good, but you can use a simple `for` loop and modify an existing list instead of creating a new one – Habib Sep 27 '13 at 14:35
@Habib You are right. I put a reference to [keyboardP's answer](http://stackoverflow.com/a/19053105/447156) which is a nice example how it can be done with `for` loop. – Soner Gönül Sep 27 '13 at 14:38

score 4 · Answer 3 · answered Sep 27 '13 at 14:37

As others have already mentioned that strings are immutable (string.Replace would return a new string, it will not modify the existing one) and you can't modify the list inside a foreach loop. You can either use a for loop to modify an existing list or use LINQ to create a new list and assign it back to existing one. Like:

emailAddresses = emailAddresses.Select(r => r.Replace(";", ",")).ToList();

Remember to include using System.Linq;

Here is what I went with ---- – Moojjoo Sep 27 '13 at 17:25 — Moojjoo, Sep 27 '13 at 17:25

score 3 · Answer 4 · edited May 23 '17 at 12:14

3

Strings are immutable so another string is returned. Try

for(int i = 0; i < emailAddress.Count; i++)
{
   emailAddress[i] = emailAddress[i].Replace(";", ",");
}

A foreach loop would not compile here because you're trying to change the iteration variable. You'd run into this issue.

edited May 23 '17 at 12:14

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answered Sep 27 '13 at 14:20

keyboardP

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`+1` for not falling into a trap with `foreach` like me `:)` – Soner Gönül Sep 27 '13 at 14:40

score 0 · Answer 5 · answered Sep 27 '13 at 14:21

0

You should use somthing like: var tmpList = new List(); add each modified email address to the tmplist and when you are done, return the TmpList. In .NET strings are inmutable, that's why your code doesnt work.

answered Sep 27 '13 at 14:21

Ale Miralles

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List emailAddress how to replace value in a particular string

5 Answers5

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