LINQ的数组元素的LIKE查询 [英] LINQ for LIKE queries of array elements

问题描述

比方说，我有一个数组，我希望做一个LINQ查询对返回那些在VARCHAR任何地方数组的元素任何记录一个varchar。

Let's say I have an array, and I want to do a LINQ query against a varchar that returns any records that have an element of the array anywhere in the varchar.

这样的事情会是甜的。


字符串[] =产业{航空公司，铁路}

string[] industries = { "airline", "railroad" }

VAR的查询=从C中的联系人那里c.industry.LikeAnyElement（行业）选择C


var query = from c in contacts where c.industry.LikeAnyElement(industries) select c

任何想法？

推荐答案

这其实是我在的防爆preSS自己presentation，的东西，是很难在常规的LINQ做;据我所知，要做到这一点最简单的方法是手动编写predicate。我用下面的例子（注意它会为 StartsWith 平等合作等）：

This is actually an example I use in my "Express Yourself" presentation, for something that is hard to do in regular LINQ; As far as I know, the easiest way to do this is by writing the predicate manually. I use the example below (note it would work equally for StartsWith etc):

    using (var ctx = new NorthwindDataContext())
    {
        ctx.Log = Console.Out;
        var data = ctx.Customers.WhereTrueForAny(
            s => cust => cust.CompanyName.Contains(s),
            "a", "de", "s").ToArray();
    }
// ...
public static class QueryableExt
{
    public static IQueryable<TSource> WhereTrueForAny<TSource, TValue>(
        this IQueryable<TSource> source,
        Func<TValue, Expression<Func<TSource, bool>>> selector,
        params TValue[] values)
    {
        return source.Where(BuildTrueForAny(selector, values));
    }
    public static Expression<Func<TSource, bool>> BuildTrueForAny<TSource, TValue>(
        Func<TValue, Expression<Func<TSource, bool>>> selector,
        params TValue[] values)
    {
        if (selector == null) throw new ArgumentNullException("selector");
        if (values == null) throw new ArgumentNullException("values");
        if (values.Length == 0) return x => true;
        if (values.Length == 1) return selector(values[0]);

        var param = Expression.Parameter(typeof(TSource), "x");
        Expression body = Expression.Invoke(selector(values[0]), param);
        for (int i = 1; i < values.Length; i++)
        {
            body = Expression.OrElse(body,
                Expression.Invoke(selector(values[i]), param));
        }
        return Expression.Lambda<Func<TSource, bool>>(body, param);
    }

}

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