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子级上的linq扩展方法

linq-to-entities

Shawn Mclean · 技术社区 · 16 年前

我创建了一个linq扩展 here . 但很显然,它不适用于对孩子的询问。如下代码所示:

return (from p in repository.GetResources()
                where p.ResourceNames.Any(r => r.Name.WhereIn(arg => arg.Name, "PartialWord"))
                select p).ToList();

我要完成的是resourcenames是一个entitycollection,我需要检查子级的属性“name”是否包含单词“partialword”。

其中工作方式如下:

repository.GetResources().WhereIn({CODEHERE});

但当放在孩子身上时,它就不起作用了。有什么特别的方法来设置我的分机吗?下面是:

public static class QueryableExtensions
{
    private static Expression<Func<TElement, bool>> GetWhereInExpression<TElement, TValue>(Expression<Func<TElement, TValue>> propertySelector, IEnumerable<TValue> values)
    {
        ParameterExpression p = propertySelector.Parameters.Single();
        if (!values.Any())
            return e => false;

        var equals = values.Select(value => (Expression)Expression.Equal(propertySelector.Body, Expression.Constant(value, typeof(TValue))));
        var body = equals.Aggregate<Expression>((accumulate, equal) => Expression.Or(accumulate, equal));

        return Expression.Lambda<Func<TElement, bool>>(body, p);
    }

    /// <summary> 
    /// Return the element that the specified property's value is contained in the specifiec values 
    /// </summary> 
    /// <typeparam name="TElement">The type of the element.</typeparam> 
    /// <typeparam name="TValue">The type of the values.</typeparam> 
    /// <param name="source">The source.</param> 
    /// <param name="propertySelector">The property to be tested.</param> 
    /// <param name="values">The accepted values of the property.</param> 
    /// <returns>The accepted elements.</returns> 
    public static IQueryable<TElement> WhereIn<TElement, TValue>(this IQueryable<TElement> source, Expression<Func<TElement, TValue>> propertySelector, params TValue[] values)
    {
        return source.Where(GetWhereInExpression(propertySelector, values));
    }

    /// <summary> 
    /// Return the element that the specified property's value is contained in the specifiec values 
    /// </summary> 
    /// <typeparam name="TElement">The type of the element.</typeparam> 
    /// <typeparam name="TValue">The type of the values.</typeparam> 
    /// <param name="source">The source.</param> 
    /// <param name="propertySelector">The property to be tested.</param> 
    /// <param name="values">The accepted values of the property.</param> 
    /// <returns>The accepted elements.</returns> 
    public static IQueryable<TElement> WhereIn<TElement, TValue>(this IQueryable<TElement> source, Expression<Func<TElement, TValue>> propertySelector, IEnumerable<TValue> values)
    {
        return source.Where(GetWhereInExpression(propertySelector, values));
    } 
}

1 回复 | 直到 16 年前

Craig Stuntz 16 年前

推定 ResourceName.Name 是一个字符串:

You don't need any extension for the string version of .Contains() in L2E . (你做仅适用于L2EV.1中的列表版本)。你应该能够做到:

return (from p in repository.GetResources()
        where p.ResourceNames.Any(r => r.Name.Contains("PartialWord"))
        select p).ToList();