Something not many people know: when you need to compare 2 strings in C#.NET you can use the == operator overload:

if(firstString == secondString)
{
    //...
}

This is case sensitive. But when you need to ignore the case please don’t use this:

if(firstString.ToLower() == secondString.ToLower())
{
    //...
}

or this:

if(firstString.ToLower().Equals(secondString.ToLower()))
{
    //...
}

A Framework provides you with utilities, please use them. They are usually better than your implementation!

Use this:

if (firstString.Equals(secondString, StringComparison.OrdinalIgnoreCase))
{
    //...
}

StringComparison is an enum. So please look at the options