Dynamic query

In addition to using LINQ syntax we can also build queries dynamically. There are two ways to build a query dynamically—using expressions and using parameters. In this section we will explain both of these two methods.

Dynamic query with expressions

First let's build a dynamic query with expressions. The following code will create two method expressions: one for the where clause and one for the order by clause:

static void TestDynamicQuery()
{
  NorthwindEntities NWEntities = new NorthwindEntities();

ParameterExpression param = Expression.Parameter(typeof(Product), '"p'");

Expression left = Expression.Property(param, typeof(Product).GetProperty('"UnitPrice'"));
Expression right = Expression.Constant((decimal)100.00, typeof(System.Nullable<decimal>));
Expression filter = Expression.GreaterThanOrEqual(left, right);
Expression pred = Expression.Lambda(filter, param);

IQueryable products = NWEntities.Products;

Expression expr = Expression.Call(typeof(Queryable), '"Where...