C# Eval Expression LINQ with Dynamic Expressions

The Z.Expressions.Eval library allows you to extend the IEnumerable<T> and IQueryable<T> interface with methods to use LINQ with dynamic expressions.

• It makes it possible and very easy by allowing dynamic queries with the same syntax as LINQ.
• You can do everything dynamically with this library that you can do with LINQ.
• The C# dynamic expression is not interpreted but compiled into LINQ expression.

Z.Expressions.Eval library supports the following LINQ method that supports predicate with a dynamic C# expression.

• Deferred
  • OrderByDescendingDynamic
  • OrderByDynamic
  • SelectDynamic
  • SelectMany
  • SkipWhile
  • TakeWhile
  • ThenByDescendingDynamic
  • ThenByDynamic
  • Where
• Immediate
  • All
  • Any
  • Count
  • First
  • FirstOrDefault
  • Last
  • LastOrDefault
  • LongCount
  • Single
  • SingleOrDefault

The following example shows how to use a predicate using a string in the LINQ dynamic method.

public static void Example1()
{
	var list = new List<char>() { 'a', 'b', 'c', 'd', 'e' };

	var myChar = list.WhereDynamic(c => "c == 'd'").FirstOrDefault();
	
	Console.WriteLine("Result: {0} ",myChar);
}

Let's consider another example where the list is sorted in descending order using the LINQ dynamic method.

public static void Example2()
{
	var list = new List<int>() { 3, 13, 9, 10, 2 };

	var newList = list.OrderByDescendingDynamic(i => "i").ToList();

     foreach (var item in newList)
     {
		Console.Write("{0}, ", item);
	}
}

You can also use the LINQ Dynamic feature in the Eval.Execute method as shown below.

public static void Example3()
{
	var list = new List<int>() { 3, 13, 9, 10, 2, 71, 34, 51, 1, 4, 19, 7 };

	var newList = list.Execute<List<int>>("Where(i => i > 10).OrderByDescending(i => i).ToList()");

	foreach (var item in newList)
	{
		Console.Write("{0}, ", item);
	}

    Console.WriteLine("");
}

Let's run the above example and you will see the following output.

71, 51, 34, 19, 13,