value type string cannot be converted to 'project.class'

hi.  I'm trying to write a bit of code that adds the ID of a member, and the name of a game to a list I've created in memory, but I'm getting the errror "value type string cannot be converted to "GameManiaApplication.StockItem" and "GameManiaApplication.Member"


My code is:
Private Sub CMDborrowgame_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CMDborrowgame.Click Dim anitemborrowed As String = "" Dim whoborrows As String = "" Dim status As Boolean = True Dim gamefound As Boolean = False whoborrows = InputBox("Enter Member ID") anitemborrowed = InputBox("Enter game title") If Not members.isMemberIDValid(whoborrows) Then MessageBox.Show("Member doesn't exist") Exit Sub End If If Not myStock.isItemA ...