It seems you didn't even write a class. Personally I think it would be better if you wrote:

class MyClass
{
public:
void MyDoSomething( const std::string & myCompareValue )
{
blablabla...
}

void MyDoSomethingOnListString(const std::string & myCompareValue )
{
for (int C = 0; C < myListString.size(); C++)
{
if (myListString[C] == myCompareValue) { MyDoSomething(myListString[C]); }
}
}

private:
std::vector myListString;

};