Is there a pattern using Linq to dynamically create a filter?

by

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).

More Related Contents:

  1. LINQ-to-SQL vs stored procedures? [closed]
  2. Linq: adding conditions to the where clause conditionally
  3. LINQ Between Operator
  4. LINQ across multiple databases
  5. LINQ: Dot Notation vs Query Expression
  6. Learning about LINQ [closed]
  7. How can I reject all changes in a Linq to SQL’s DataContext?
  8. Operation could destabilize the runtime?
  9. LINQ with SQLite (linqtosql)
  10. How to create a dynamic LINQ join extension method
  11. LINQ not updating on .SubmitChanges()
  12. How to dynamically add OR operator to WHERE clause in LINQ
  13. LINQ To SQL exception: Local sequence cannot be used in LINQ to SQL implementation of query operators except the Contains operator
  14. Linq To Sql – Dynamic OrderBy – Case When
  15. Linq to SQL how to do “where [column] in (list of values)”
  16. Multiple WHERE clause in Linq
  17. How do I write this cross apply query in LINQ-to-SQL?
  18. Point connectionstring in dbml to app.config
  19. Building Dynamic LINQ Queries based on Combobox Value
  20. NHibernate vs LINQ to SQL
  21. Returning IEnumerable vs. IQueryable
  22. ‘Contains()’ workaround using Linq to Entities?
  23. Entity framework linq query Include() multiple children entities
  24. Understanding .AsEnumerable() in LINQ to SQL
  25. Am I misunderstanding LINQ to SQL .AsEnumerable()?
  26. Entity Framework – “Unable to create a constant value of type ‘Closure type’…” error
  27. EF 4: Removing child object from collection does not delete it – why?
  28. Max or Default?
  29. Last and LastOrDefault not supported
  30. Linq “Could not translate expression… into SQL and could not treat it as a local expression.”

Leave a Comment