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c# - LinqKit Predicate Or with Contains 计算为等于

问题描述

我正在搜索我的应用程序。搜索工作除了当用户的搜索通过搜索相关实体进行级联时。我已经调试了代码并测试了 Entity Framework 生成的 SQL。我发现问题是Contains()在 SQL 中应该是“LIKE”时转换为“=”。Contains()按照我对 FirstName、MiddleName 等的初始谓词的预期工作，但不在if (cascade)代码块中。

我的 C# 搜索逻辑：

public IList<Individual> Find(string search, bool cascade, bool includeInactive)
{
    _context.Database.Log = s => System.Diagnostics.Debug.WriteLine(s);
    IQueryable<Individual> query = _context.Individuals;
    if (!string.IsNullOrWhiteSpace(search))
    {
        search = search.Trim();
        string[] searchParts = search.Split(' ');
        ExpressionStarter<Individual> predicate = PredicateBuilder.New<Individual>(false);
        foreach (string searchPart in searchParts)
        {
            predicate = predicate.Or(c =>
                c.FirstName.Contains(searchPart) || c.MiddleNames.Contains(searchPart) ||
                c.LastName.Contains(searchPart) || c.PreferredName.Contains(searchPart));
            if (cascade)
            {
                predicate = predicate.Or(c =>
                    c.IndividualOrganisationGroups.Select(og => og.OrganisationGroup).Select(g => g.Group.Name)
                        .Contains(searchPart));
            }
        }
        query = query.Where(predicate);
    }
    if (!includeInactive)
    {
        query = query.Where(c => c.Active);
    }
    return query.ToList();
}

从 EF 生成的 SQL：

SELECT 
    [Extent1].[ID] AS [ID], 
    [Extent1].[RegistrationTypeID] AS [RegistrationTypeID], 
    [Extent1].[Title] AS [Title], 
    [Extent1].[FirstName] AS [FirstName], 
    [Extent1].[MiddleNames] AS [MiddleNames], 
    [Extent1].[LastName] AS [LastName], 
    [Extent1].[PreferredName] AS [PreferredName], 
    [Extent1].[RegistrationNumber] AS [RegistrationNumber], 
    [Extent1].[Username] AS [Username], 
    [Extent1].[AzureID] AS [AzureID], 
    [Extent1].[Notes] AS [Notes], 
    [Extent1].[Active] AS [Active], 
    [Extent1].[CreatedDate] AS [CreatedDate], 
    [Extent1].[CreatedBy] AS [CreatedBy], 
    [Extent1].[UpdatedDate] AS [UpdatedDate], 
    [Extent1].[UpdatedBy] AS [UpdatedBy]
    FROM [dbo].[Individual] AS [Extent1]
    WHERE ([Extent1].[FirstName] LIKE @p__linq__0 ESCAPE '~') OR ([Extent1].[MiddleNames] LIKE @p__linq__1 ESCAPE '~') OR ([Extent1].[LastName] LIKE @p__linq__2 ESCAPE '~') OR ([Extent1].[PreferredName] LIKE @p__linq__3 ESCAPE '~') OR ( EXISTS (SELECT 
        1 AS [C1]
        FROM   [dbo].[IndividualOrganisationGroup] AS [Extent2]
        INNER JOIN [dbo].[OrganisationGroup] AS [Extent3] ON [Extent2].[OrganisationGroupID] = [Extent3].[ID]
        INNER JOIN [dbo].[Group] AS [Extent4] ON [Extent3].[GroupID] = [Extent4].[ID]
        WHERE ([Extent1].[ID] = [Extent2].[IndividualID]) AND (([Extent4].[Name] = @p__linq__4) OR (1 = 0))
    ))
-- p__linq__0: '%screen%' (Type = AnsiString, Size = 8000)

-- p__linq__1: '%screen%' (Type = AnsiString, Size = 8000)

-- p__linq__2: '%screen%' (Type = AnsiString, Size = 8000)

-- p__linq__3: '%screen%' (Type = AnsiString, Size = 8000)

-- p__linq__4: 'screen' (Type = AnsiString, Size = 8000)

有问题的 SQL（最后一个 WHERE 子句）：

WHERE ([Extent1].[ID] = [Extent2].[IndividualID]) AND (([Extent4].[Name] = @p__linq__4) OR (1 = 0))

它应该是什么样子：

WHERE ([Extent1].[ID] = [Extent2].[IndividualID]) AND (([Extent4].[Name] LIKE @p__linq__4) OR (1 = 0))

所以我的问题是，如何在我的实体框架 SQL 中将此代码转换为 LIKE？

predicate = predicate.Or(c =>
                    c.IndividualOrganisationGroups.Select(og => og.OrganisationGroup).Select(g => g.Group.Name)
                        .Contains(searchPart));

标签： c#entity-frameworklinqkit

解决方案

它与 LINQKit PredicateBuilder 无关。原因是结果

c.IndividualOrganisationGroups.Select(og => og.OrganisationGroup).Select(g => g.Group.Name)

is IEnumerable<string>(or IQueryable<string>)，所以你正在使用Enumerable(or Queryable)Contains方法而不是string.Contains其他地方的 as。

而不是Select+ Contains，您真正需要的是Any扩展方法。

您的示例最简洁的语法是：

c => c.IndividualOrganisationGroups
    .Any(og => og.OrganisationGroup.Group.Name.Contains(searchPart))

当然，如果您需要检查更多属性Group（甚至不检查），请使用Select+ Any：

c => c.IndividualOrganisationGroups
    .Select(og => og.OrganisationGroup.Group)
    .Any(g => g.Name.Contains(searchPart))

或者通过以“正常”方式编写查询，将带有过滤器的集合转换为单个布尔值的最自然方式。例如Select，Where等等，并将无参数Any放在最后：

c => c.IndividualOrganisationGroups
    .Select(og => og.OrganisationGroup.Group)
    .Where(g => g.Name.Contains(searchPart))
    .Any())

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