Question

我有以下查询执行＆＃34; AND＆＃34;点播：

var products = // Selecting a list of products in anywhere based in a filter...

foreach (var product in products)
{
    query = query.Where(p => p.Code == product.Code); // with this way, this query make no sense because this happens in any scenario, never a code can be more than one code.
}

那么，我怎么能做同样的查询，但执行＆＃34; OR＆＃34;按需（以便查询有意义）？

Answer 1

使用Contains：

var codes = products.Select(x => x.Code).ToArray();

query.Where(p => codes.Contains(p.Code));

Answer 2

您可以将IN的传真用于LINQ：

var productCodeList = products.Select(p => p.Code).ToList();

query = query.Where(p => productCodeList.Contains(p.Code));

基本上是说：

SELECT   *
FROM     products
WHERE    code IN (<list_of_codes>)

Answer 3

使用广告Brad和Joe写的Contains方法，或者（当不可能的话）使用PredicateBuilder:

var predicate = PredicateBuilder.False<Product>();

foreach (var product in products)
{
    var code = product.Code;
    predicate = predicate.Or(p => p.Code == code);
}

var products dataContext.Products.Where(predicate);

对于Linq对实体的“OR”按需，我该怎么办？

3 个答案: