Dynamic LINQ (Part 1: Using the LINQ Dynamic Query Library)
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by Scott Guthrie
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Simple Dynamic Query Library Example

You can use the DynamicQuery library against any LINQ data provider (including LINQ to SQL, LINQ to Objects, LINQ to XML, LINQ to Entities, LINQ to SharePoint, LINQ to TerraServer, etc).  Instead of using language operators or type-safe lambda extension methods to construct your LINQ queries, the dynamic query library provides you with string based extension methods that you can pass any string expression into.

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:

Figure 2

Using the LINQ DynamicQuery library I could re-write the above query expression instead like so:

Figure 3

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).


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