我如何从字符串制作动态Lambda表达式? [英] How i can make dynamic lambda Expression from string?

问题描述

我需要在方法中使用Lambda表达式

I need use Lambda Expression in my method

public static class QueryableDynamicExtension
{
    public static IQueryable<T> DynamicEquals<T>(
       this IQueryable<T> query,
       string field,
       object value)
    {
        Expression<Func<T, bool>> expr = ???                   

        return query.Where(expr);
    }
}

在这种方法中，我希望它的返回结果与

In this method, I want it return same as

IQueryable<Article> articles = new ModelDataContext().Articles.Where(m => m.CategoryId == 5);
// I want replace by
IQueryable<Article> articles = new ModelDataContext().Articles.DynamicEquals("CategoryId", 5);

在这种情况下，我应该如何构建"expr"?请帮忙.

How should I build the "expr" in this case? Please help.

推荐答案

您可以将动态LINQ库作为

You could look into the Dynamic LINQ library, as blogged by Scott Gu here. I've used this previously where I've built a rules-based product system for work, and have used dynamic expressions stored in our database layer to provide additional expressions to filter out product sets.

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