Using Linq to filter SQL based on Lists (or arrays)

Here is handy way of filtering your results based on passed in lists, which can be null.

The key is to handle the empty list case in the where clause using list.Count == 0 || . This will allow you to generate the appropriate query

public List GetData(List Numbers, List Letters)

{

if (Numbers == null)

Numbers = new List();

if (Letters == null)

Letters = new List();

var q = from d in database.table

where (Numbers.Count == 0 || Numbers.Contains(d.Number))

where (Letters.Count == 0 || Letters.Contains(d.Letter))

select new Data

{

Number = d.Number,

Letter = d.Letter,

};

return q.ToList();

}