Question

有：

输入参数CompanyName。

API /搜索/公司的companyName =柏＆安培;页= 1＆安培;限制= 20

任务：在Companies之前获取CompanyName，在每个Industry中获取Company：

查询：

 var query = (from company in _context.Companies
                         where company.Name.Contains(model.Model.CompanyName.Trim())
                         join ci in _context.CompanyIndustries on company.Id equals ci.CompanyId
                         join industry in _context.Industries on ci.IndustryId equals industry.Id

                         select new SearchCompanyModel()
                         {
                             Id = company.Id,
                             Name = company.Name,
                             Logo = company.LogoUrl,
                             Industry = industry.Name
                         })
                         .GroupBy(x => new {x.Id, x.Name, x.Logo})
                         .Select(x => new SearchCompanyModel
                {
                    Id = x.Key.Id,
                    Name = x.Key.Name,
                    Logo = x.Key.Logo,
                    Industry = x.FirstOrDefault().Industry
                });

Answer 1

您可以使用加入

void Main()
{
    var allCompanies = new Company[] {
        new Company{Id = "1", Name = "c1"}, 
        new Company{Id = "2", Name = "c2"}, 
        new Company{Id = "3", Name = "c2"}
    };

    var allIndustries = new Industry[] {
        new Industry{Id = "1", Name = "i1"}, 
        new Industry{Id = "2", Name = "i2"}, 
        new Industry{Id = "3", Name = "i3"}
    };

    var allCompanyIndustries = new CompanyIndustry[] {
        new CompanyIndustry{CompanyId = "1", IndustryId = "1"}, 
        new CompanyIndustry{CompanyId = "1", IndustryId = "2"}, 
        new CompanyIndustry{CompanyId = "3", IndustryId = "1"}
    };

    var companyName = "c1";
    var companies = allCompanies
        .Where(company => company.Name == companyName)
        .Join(allCompanyIndustries, c => c.Id, ci => ci.CompanyId, (c, i) => new {Company = c, IndustryId = i.IndustryId})
        .Join(allIndustries, ci => ci.IndustryId, i => i.Id, (ci, i) => new {Company = ci.Company, Industry = i})
        .ToArray();
}

class Company {
    public string Id {get;set;}
    public string Name {get;set;}
}

class Industry {
    public string Id {get;set;}
    public string Name {get;set;}
}

class CompanyIndustry {
    public string CompanyId {get;set;}
    public string IndustryId {get;set;}
}

Answer 2

您可以尝试多种优化，但如果使用非映射对象类型的属性（即model.Model.CompanyName.Trim（）），则可能会阻止查询被缓存（请参阅{{3 }}）

幸运的是，这很容易修复，只需将值缓存在查询之外的局部变量中，然后使用此值

var companyName = model.Model.CompanyName.Trim();

这可能会有所帮助，但我提供链接的文章还包含许多其他建议。

LINQ to SQL如何优化查询？

2 个答案: