<p>Is there a pattern using Linq to dynamically create a filter?</p>

<p>I have the need to create custom filtering on a list, in the past I would just dynamically create the SQL...it doesn't seem like this is possible with Linq.</p>

Check out the
Dynamic Linq Library
from ScottGu's blog:
For example, below is a standard type-safe LINQ to SQL VB query that retrieves data from a Northwind database and displays it in a ASP.NET GridView control:
```
```
Dim Northwind As New NorthwindDataContext
Dim query = From q In Northwind.Products Where p.CategoryID = 2 And p.UnitPrice > 3 Order By p.SupplierID Select p

Gridview1.DataSource = query
GridView1.DataBind()
```
```
Using the LINQ DynamicQuery library I could re-write the above query expression instead like so
```
```
Dim Northwind As New NorthwindDataContext
Dim query = Northwind.Products .where("CategoryID=2 And UnitPrice>3") . OrderBy("SupplierId")
Gridview1.DataSource = query
GridView1.DataBind()
```
```
Notice how the conditional-where clause and sort-orderby clause now take string expressions instead of code expressions.  Because they are late-bound strings I can dynamically construct them.  For example: I could provide UI to an end-user business analyst using my application that enables them to construct queries on their own (including arbitrary conditional clauses).