Adding filter expressions dynamically to an array

Question

I have this example which creates 3 expressions and adds them to one array of expression. Now i'd like to know how to do the same in a loop, for a unknown number of expressions.

Expression<Func<Product, bool>> filter1 = c => c.City.StartsWith("S");
Expression<Func<Product, bool>> filter2 = c => c.City.StartsWith("M");
Expression<Func<Product, bool>> filter3 = c => c.ContactTitle == "Owner";

Expression<Func<Product, bool>>[] filterExpressions = new Expression<Func<Product, bool>>[] { filter1, filter2, filter3 };

@Arion good question. TysHTTP - It's not clear where is that you're 'stuck' here. I'm guessing it's a dynamic nature of things in some way. — NSGaga
– NSGaga, Commented Apr 15, 2012 at 14:49

Justin Niessner · Accepted Answer · 2012-04-15 14:49:26Z

11

Use a List instead of an Array:

var filterExpressions = new List<Expression<Func<Product, bool>>>
    { filter1, filter2, filter3 };

filterExpressions.Add(c => c.Name.StartsWith("J"));

And then if you, for some reason, need to pass the list to a method that only takes an Array you can use the ToArray() method:

var filterExpressionsArray = filterExpressions.ToArray();

answered Apr 15, 2012 at 14:49

Justin Niessner

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2 Comments

BrokenGlass Over a year ago

Working with expressions you'd think OP would know this - but I guess given the question as is, this is the only answer that can be given at this point.

Tys Over a year ago

Sorry, i already fixed it some other way. I guess i just forgot how a list could help me here. I updated my code to List.ToArray(). Thanks!

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