c# Exists() causing error CS0135

Why does the Exist() not work here?

if(listOfPlayers.Exists(listOfPlayers => listOfPlayers.netID == uniqueId) == false)
{
  foreach(NetworkUser user in listOfPlayers)
  {
    if(user.active == false)
    {
      user.netPlayer = Network.player;	// NetworkPlayer object
      uniqueId = user.netID;
      user.characterName = characterName;
      user.characterClass = characterClass;
      user.active = true;
      user.netPlayer = networkPlayer;
      user.characterLevel = characterLevel;
					
      break;
    }
  }
}

error on line 1:

error CS0135: listOfPlayers’ conflicts with a declaration in a child block`

I have problems figuring out what this error means for me.

sorry, it was a simple syntax issue. This is how the Exists() should look like:

if(listOfPlayers.Exists(item => item.netID == uniqueId) == false)
{
  ...
}