Lambda shiz

Linqpad.cs

void Main()
{
        GetExpression().Compile()(new Foo { Bar = new Bar { Abc = "A" }}).Dump();
        GetExpression().Compile()(new Foo { Bar = new Bar { Abc = "B" }}).Dump();
}

Expression<Func<Foo, bool>> GetExpression()
{

	// Method takes Foo and uses an expression to first retrieve Bar
	// Then it uses that to verify if Bar.Abc is equal to something
	
	Expression<Func<Foo, Bar>> getBarExpression = foo => foo.Bar;
	Expression<Func<Bar, bool>> verifyBar 		= bar => bar.Abc != "B";
	
	var parameterExpression = Expression.Parameter(typeof(Foo), "foo");
	var parameterExpression2 = Expression.Parameter(typeof(Bar), "bar");

	// First invoke foo => foo.Bar to get Bar
	var barResultExpression = Expression.Invoke(getBarExpression, parameterExpression);
	var resultExpression = Expression.Invoke(verifyBar, barResultExpression);
	// Give me the combined expression
	return Expression.Lambda<Func<Foo, bool>>(resultExpression, parameterExpression);
}


// Define other methods and classes here

class Foo
{
    public Bar Bar { get; set;}
}

class Bar 
{
    public string Abc {get;set;}
}