Question: My current RegEx for phone number validation is `^\d{8,}$` which validates minimum length is 8 and does not allow special characters or letters and my question is what's the RegEx which does not allow 9-15 consecutive duplicate numbers plus the current condition (minimum length is 8 and no special characters or letters allowed).

Thanks...

Answer: 
If I understand your requirements correctly, this regex will do it:

```js
/^(?!.*(\d)\1{8})\d{8,}$/

```

Here is a commented version (in C# syntax):

```cs
Regex regexObj = new Regex(@"
    # Match digits sequence  with no same digit 9 times in a row.
    ^                # Anchor to start of string
    (?!.*(\d)\1{8})  # Assert no digit repeats 9 times.
    \d{8,}           # Match eight or more digits.
    $                # Anchor to end of string", 
    RegexOptions.IgnorePatternWhitespace);

```
So `11111111` (8 `1`s) is ok, but `111111111` (9 `1`s) isn't?

A regex isn't *always* the right answer. I'd keep the existing `^\d{8,}$` regex and then check for repeated digits separately. Since you're only (for now?) forbidding 10 distinct numbers, you could just set up a hash of forbidden numbers and check against it:

```
my %forbidden = map { $_ x 9 => 1 } 0..9;

...

if ($num =~ /^\d{8,}$/ and not $forbidden{$num}) {
    # accept
}
else {
    # reject
}

```