LINQ to SQL 查询以确定值是否以数字开头

LINQ to SQL query to determine if value starts with numeric(LINQ to SQL 查询以确定值是否以数字开头)

问题描述

我有一个项目，我通过首字母查询用户:

I have a project where I query users by first letter:

repository.GetAll().Where(q => q.BrukerIdent.StartsWith(letter.ToString())).ToList();

..where repository.GetAll() 返回一个 IQueryable，BrukerIdent 是一个包含用户名的字符串，letter 是一个传入的字符值.这很好用，除了我还想获得以数字开头的用户.而且我不想按单独的数字排序.

..where repository.GetAll() returns an IQueryable<Bruker>, BrukerIdent is a string that contains the username, and letter is a char-value coming in. This works perfectly, except that I also want to get users that starts with digits. And I don't want to sort by separate digits.

我的脑海里呼喊着 StartsWith("d") 但据我所知，它不是这样工作的.我也想过做一个 10 路 OR 子句，但这看起来像意大利面条，我不确定效率.

My mind yells for a StartsWith("d") but as far as I have found out it doesn't work this way. I have also thought of doing a 10-way OR clause, but that would look like spaghetti, and I'm not sure of the efficiency.

有没有什么正确"的方法可以做到这一点?

Is there any "right" way to do it like this?

推荐答案

repository.GetAll().Where(q => Char.IsNumber(q.BrukerIdent[0]))

MSDN

var numbers = Enumerable
                     .Range(0, 10)
                     .Select(i => i.ToString(CultureInfo.InvariantCulture));

// var numbers = new[] { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 );
// var numbers = HashSet<int> { ... };

var q = from b in repository.GetAll()
        where numbers.Contains(b.BrukerIdent.FirstOrDefault())) //[0]
        select b;

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