Question

Given the following string arrray:

string[] ranges = new string[]{"0-100", "100-200", "500-1000"};

I would like to dynamically express this in a linq expression – Something along the lines of:

var query = from p in Db.Products()
            where p.Amount() >= 0
            where p.Amount() <= 100
            where p.Amount() >= 101
            where p.Amount() <= 200
            where p.Amount() >= 500
            where p.Amount() <= 1000
            select p;

I know how to extract the values from the array so that’s not the issue, but more so how do i dynamically build the linq expression in a for loop:

string[] ranges = new string[]{"0-100", "100-200", "500-1000"};

foreach (var item in ranges)
{
    int min = int.Parse(item.Split('-').First());
    int max = int.Parse(item.Split('-').Last());                
    //Linq expression?
}

Answer 1

Like this:

IQueryable<Product> query = DB.Products();
foreach (var item in ranges)
{
    int min = int.Parse(item.Split('-').First());
    int max = int.Parse(item.Split('-').Last());                
    query = query.Where(p => p.Amount() >= min && p.Amount() <= max);
}

(I’ve only got half the where clauses you had, but it’s equivalent. You can break it up if you really want.)

Note the assignment back to query – methods like Where return a new query which is the result of applying the operation to the existing query; they don’t change anything in the existing query.