// Define an expression tree, taking an integer, returning a bool.
Expression<Func<int, bool>> expr = num => num < 5;
// Call the Compile method on the expression tree to return a delegate that can be called.
Func<int, bool> result = expr.Compile();
// Invoke the delegate and write the result to the console.
Console.WriteLine(result(4)); // Prints true
// Prints True.
// You can also combine the compile step with the call/invoke step as below:
Console.WriteLine(expr.Compile()(4));