c# - regex to remove vowels from string except first and last character

Question

I am trying to remove all the vowels from a string except for the first and last character. I have tried with 2 expressions and using 2 ways but in vain. I have described them below. Does anybody has a regular expression for this? e.g. original string -- source = apeaple after regex -- source_modified = apple (this is what is expected) I tried the expression `([a-zA-Z])[aeiouAEIOU]([a-zA-Z])` but this expression is removing repeated character as well. So the following is happening when i apply the above expression code used -- ``` Regex reg = new Regex("([a-zA-Z])[aeiouAEIOU]([a-zA-Z])"); string source_modified = reg.Replace(source, ""); ``` original string -- source = apeaple after code execution -- source_modified = aple (repeating character removed) code used -- `string source_modified = Regex.Replace(source, "([a-zA-Z])[aeiouAEIOU]([a-zA-Z])", "$1" + "$2");` original string -- source = apeaple after code execution -- source_modified = apaple (just 1 vowel gets removed) i also trie…

Accepted Answer

You need some lookaround like so

```
(?<!^)[aouieyAOUIEY](?!$)
```

C# supports it and it's very powerful

```
string resultString = null;
try {
    resultString = Regex.Replace(subjectString, "(?<!^)[aeui](?!$)", "");
} catch (ArgumentException ex) {
    // Syntax error in the regular expression
}
```

Update 1

T.W.R.Cole informs me that there is a special rule in the English language ("this doesn't work for words like "Anyanka" where an inner 'y' is used as a consonant")

The following change should do this, using the technique of negative lookahead:

```
(?<!^)([aouie]|y(?![aouie]))(?!$)
```

This time enable the regex modifier that matches case insensitive, it makes the regex simpler than the original

if a y followed by another y still means that the y is a consonant (euh... is there such a word) and thus should not disappear than a y must be listed in the last character class as well :

```
(?<!^)([aouie]|y(?![aouiey]))(?!$)
```

I repeat that I used C# as my regex dialect which has good support for lookaround techniques.

c# - regex to remove vowels from string except first and last character

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