PredicateBuilder + Join + VB.NET - vb.net

Question

I have a db that contains 3 tables
Products Table Suppliers Table Categories Table
Id Id Id
ProductName SupplierName CategoryName
Quantity . .
SupplierId . .
CategoryId
.
.
I am using PredicateBuilder to select Product accoring to the selected product field (Quantity,Productname...)
How Can I use PredicateBuilder or any other method to Select the Product according to Its Suppliername or Categoryname
Please I am using VB.NET I saw many C# examples but I can not understand it nor translate it
I am thinking of using join in predicateBuilder but I do not how !!!!
To be more clear What I want is to combine multiple field in one search ,Like for example:
Give me a Product where It's Name contains "s" and Quantity <10 and SupplierName is Kimo
Give me a product where i's name contains "g" only
give me the products for categoryName "Machines"
.
.
And this search predicate is changable because Each Products table has many fields ,So the search is dynamic according to selected fields
Waiting for your kind help.
I think Arion answer was correct but It needs some revision
AnyWay I came up with this solution ,It is not the most effecient one but It solved my problem.
Dim SupplierAlso As String = ""
Dim CategoryAlso As String = ""
Dim pred = PredicateBuilder.True(Of Products)()
Select Case Entry
Case "Number"
Dim Inum = Entry
pred = pred.And(Function(m As products) m.ID.Equals(CInt(Inum)))
Case "ProductName"
Dim IName = Entry
pred = pred.And(Function(m As Products) m.ProductName.IndexOf(IName, StringComparison.OrdinalIgnoreCase) >= 0)
.
.
.
Case "Supplier"
SupplierAlso = Entry
Case "Category"
CategoryAlso = Ent
Next
Dim f As ProductsDataTable = Products.Product
Dim tmp As IEnumerable(Of Products) = New ProductsDataTable().AsEnumerable()
tmp = f.AsEnumerable.Where(pred.Compile)
Dim qry
If CategoryAlso = "" And SupplierAlso = "" Then
q = (From prods In tmp
Join Cats In Categories
On prods.CategoryId Equals Cats.ID
Join Supps In Suppliers
On Supps.ID Equals prods.SupplierId
Select Supps.SupplierName, Cats.CategoryName, prods.ID _
, prods.ProductName, prods.UnitPrice, prods.CategoryId _
, prods.SupplierId, prods.Location, _
prods.Description, prods.SellPrice, prods.CountInStock _
, prods.ProductionDate, prods.ExpiryDate, _
prods.ProductType, prods.ProductSeason).ToList
ElseIf CategoryAlso <> "" And SupplierAlso <> "" Then
q = (From prods In tmp
Join Cats In Categories
On prods.CategoryId Equals Cats.ID
Join Supps In Suppliers
On Supps.ID Equals prods.SupplierId
Where Cats.CategoryName.IndexOf((CategoryAlso)
, StringComparison.OrdinalIgnoreCase) >= 0 And _ Supps.SupplierName.IndexOf((SupplierAlso), _
StringComparison.OrdinalIgnoreCase) >= 0
Select Supps.SupplierName, Cats.CategoryName, prods.ID, _
prods.ProductName, prods.UnitPrice, prods.CategoryId, _
prods.SupplierId, prods.Location, _
prods.Description, prods.SellPrice, prods.CountInStock, _
prods.ProductionDate, prods.ExpiryDate, _
prods.ProductType, prods.ProductSeason).ToList
ElseIf SupplierAlso <> "" And CategoryAlso = "" Then
q = (From prods In tmp
Join Cats In Categories
On Cats.ID Equals prods.CategoryId
Join Supps In Suppliers
On prods.SupplierId Equals Supps.ID Where _
Supps.SupplierName.IndexOf((SupplierAlso), _
StringComparison.OrdinalIgnoreCase) >= 0
Select Cats.CategoryName, Supps.SupplierName, prods.ID, _
prods.ProductName, prods.UnitPrice, prods.CategoryId, _
prods.SupplierId, prods.Location, _
prods.Description, prods.SellPrice, prods.CountInStock, _
prods.ProductionDate, prods.ExpiryDate, _
prods.ProductType, prods.ProductSeason).ToList
ElseIf CategoryAlso <> "" And SupplierAlso = "" Then
q = (From prods In tmp
Join Cats In Categories
On prods.CategoryId Equals Cats.ID Where Cats.CategoryName.IndexOf _
((CategoryAlso), StringComparison.OrdinalIgnoreCase) >= 0
Join Supps In Suppliers On Supps.ID Equals prods.SupplierId
Select Supps.SupplierName, Cats.CategoryName, prods.ID, _
prods.ProductName, prods.UnitPrice, prods.CategoryId, _
prods.SupplierId, prods.Location, _
prods.Description, prods.SellPrice, prods.CountInStock, _
prods.ProductionDate, prods.ExpiryDate, _
prods.ProductType, prods.ProductSeason).ToList
End If
For Each it In q
With it
DataGridView2.Rows.Add _
({.ID, .ProductName, .UnitPrice, .categoryname, .suppliername, .Location, _
.Description, .SellPrice, .CountInStock, _ .ProductionDate, .ExpiryDate, _
.ProductType, .ProductSeason})
End With
Next
So what do you think ,Is there a better way? Ofcourse yes?Silly question ,But Where?

Answer 1

So i would do something like this then. I have simplify the where statements but I think you will get my point:
dim checkCategoryName as boolean=true
dim checkSupplier as boolean=true
dim checkQuantity as boolean=true
dim query= db.Products.Select (function(p) p)
if checkCategoryName then
query=query _
.Where (function(p) db.Categories.Where (function(c) c.CategoryName="??" ) _
.Select (function(c) c.Id) _
.Contains(p.CategoryId))
end if
if checkSupplier then
query=query _
.Where (function(q) db.Suppliers.Where (function(s) s.SupplierName="??") _
.Select (function(s) s.Id) _
.Contains(q.SupplierId))
end if
if checkQuantity then
query=query.Where (function(q) q.Quantity<10)
end if
dim result=query.ToList()
Where db is the linq data context.