Question LINQ expression with variable number of expressions

[breakoutfoo]

Hi,

I am creating a form that searches for items based upon search criteria entered into multiple free text fields. None of the fields are to be mandatory and as such I need to be able to write my LINQ in such a way that the conditions to be used can change.

I have around 10 possible fields so there are too many combinations to create a seperate LINQ for each possible combination. I have no idea how to tackle this. Does anybody have any suggestions of the sort of methods I should be looking to use?

Thanks

Andy

Andy

 

[jmcilhinney]

One of the cool features of LINQ is the ability to use function syntax to dynamically compose a query that will only be evaluated when the data is actual data is used, e.g.

Dim products = myDataContext.Products

If Me.nameTextBox.TextLength > 0 Then
    products = products.Where(Function(p) p.Name = Me.nameTextBox.Text)
End If

If Me.priceTextBox.TextLength > 0 Then
    products = products.Where(Function(p) p.Price = CDec(Me.priceTextBox.Text))
End If

When you actually use the data, all those Where clauses get combined into one. You can do the same with other clauses to, e.g. OrderBy or OrdeByDescending.