在Include语句中使用Where子句的Linq查询 [英] Linq Query with a Where clause in an Include statement

问题描述

我正在尝试替换我的笨拙的大查询；虽然很丑陋，但是可以按需工作:-

I am trying to replace my big, ugly query; although ugly it works as desired:-

using (var ctx = new Data.Model.xxxTrackingEntities())
{
    var result = ctx.Offenders
        .Join(ctx.Fees, o => o.OffenderId, f => f.OffenderId,
        (o, f) => new { Offenders = o, Fees = f })
        .Join(ctx.ViolationOffenders, o => o.Fees.ViolationId, vo => vo.ViolationId,
        (o, vo) => new { Offenders = o, ViolationOffenders = vo })
        .Join(ctx.Violations, v => v.ViolationOffenders.ViolationId, vo => vo.ViolationId,
        (v, vo) => new { Violations = v, ViolationOffenders = vo })
        .Where(o => o.Violations.Offenders.Offenders.YouthNumber != "")
        .ToList();

    gvwData.DataSource = result;
}

使用以下linq查询:-

with the following linq Query:-

 var result = ctx.Offenders
        .Include(o => o.Fees.Where(f => f.Amount != null))
        .Include(o => o.ViolationOffenders)
        .Include(o => o.ViolationOffenders.Select(of => of.Violation))
        .Where(o => o.YouthNumber != "" && o.FirstName != "")
        .ToList();

我正在查询的第二行...添加了where子句之后... o => o.Fees.Where(f=> f.Amount != null)

I am blowing up on the 2nd line of the query... once I add the Where clause... o => o.Fees.Where(f=> f.Amount != null)

我收到的错误消息...

The error message I get...

包含路径表达式必须引用在类型上定义的导航属性.使用虚线路径作为参考导航属性，使用选择"运算符作为集合导航属性.

The Include path expression must refer to a navigation property defined on the type. Use dotted paths for reference navigation properties and the Select operator for collection navigation properties.

此外，我尝试将查询编写为:-

In addition, I tried writing my query as:-

   var result = ctx.Offenders
        .Include(o => o.Fees)
        .Include(o => o.ViolationOffenders)
        .Include(o => o.ViolationOffenders.Select(of => of.Violation))
        .Where(o => o.YouthNumber != "" && o.FirstName != "" && o.Fees.Where(f=> f.Amount != null))
        .ToList();

但随后出现以下错误:-

But then I get the following error:-

&&"运算符不能应用于类型为'bool'和'System.Collections.Generic.IEnumerable

Operator '&&' cannot be applied to operands of type 'bool' and 'System.Collections.Generic.IEnumerable

我知道这个概念是正确的，但是我需要语法方面的帮助.

I know the concept is right, but I need help with the syntax.

推荐答案

在Where内不能有Where，但是可以使用Any来返回布尔值

You cant have a Where inside the Where, but you can use Any which will return a boolean

var result = ctx.Offenders
    .Include(o => o.Fees)
    .Include(o => o.ViolationOffenders)
    .Include(o => o.ViolationOffenders.Select(of => of.Violation))
    .Where(o => o.YouthNumber != "" && o.FirstName != "" 
        && o.Fees.Any(f=> f.Amount != null)) // here
    .ToList();

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