c# If else statement with case insensative

c# If else statement with case insensative

I have this if else statement which is assigned to compare results from a
text box to a list of context. I am wondering how do i make it such that
it is case insensitive ?
value = textbox1.Text;
if (article.contains(value))
{
label = qwerty;
}
else
{
break;
{