[c#] Not equal string

I'm trying to set a condition like this

if (myString=!"-1")
{
  //Do things
}

But it fails. I've tried

if(myString.Distinct("-1")) 
{
  //Do things
}

but it doesn't work either.

With Equals() you can also use a Yoda condition:

if ( ! "-1".Equals(myString) )

Try this:

if(myString != "-1")

The opperand is != and not =!

You can also use Equals

if(!myString.Equals("-1"))

Note the ! before myString