c# extensions

i typically progression methods unequivocally sparingly. i feel compelled an progression method, i infrequently wish profusion method. doubt is, your thoughts progression methods job progression methods? bad practice? feels wrong, nonetheless i can't unequivocally interpretation why.

for example, second caselessis slight calls first:

public stationary bool caselessis(this twine s, twine compareto)
{
    relapse string.compare(s, compareto, true) == 0;
}

public stationary bool caselessis(this twine s, ienumerable<string> compareto)
{
    foreach(string comparison compareto)
    {
        (s.caselessis(comparison))
        {
            relapse true;
        }
    }

    relapse false;
}

would some-more suitable this? downside violates dry.

public stationary bool caselessis(this twine s, twine compareto)
{
    relapse string.compare(s, compareto, true) == 0;
}

public stationary bool caselessis(this twine s, ienumerable<string> compareto)
{
    foreach(string comparison compareto)
    {
        (string.compare(s, comparison, true) == 0)
        {
            relapse true;
        }
    }

    relapse false;
}