SQL Query - Searching Database Using Filters?

I'm currently searching a database using filters. The user can use any or all of them, and to achieve this, I have the following

Private Sub GetData()
Dim QueryString As String = "SELECT * FROM Inventory WHERE"
Dim FiltersExist As Boolean = False
'Set Up Connection to Database
[Code] ....

I would like to create this using the query builder instead, but I don't know how to tell it to ignore a parameter if its value is null or an empty string. Another problem with the way I'm doing it now is that if the user has filtered the results, then adds a record, I cannot use the Update method of my TableAdapter, because the datasource of my DGV has changed. Even if I can't achieve what I want with the Query Builder.