StartsWith 与列表中的任何字符串到 SQL 请求与 LINQ 和实体框架

Question

我可以通过这样的请求从 EF 获取对象：

apples = apples.Where(a => a.Sort.Name.StartsWith("Gold"))

但我想知道是否可以使用字符串列表而不是一个字符串？ 我已经尝试过这样做：

List<string> list = {...}

apples = apples.Where(a => list.Any(x => a.Sort.Name.StartsWith(x)))

但它给了我奇怪的错误：

System.ArgumentOutOfRangeException：指定的参数超出了有效值的范围。 (Parameter 'index') at System.Linq.Expressions.InstanceMethodCallExpression1.GetArgument(Int32 index) at Npgsql.EntityFrameworkCore.PostgreSQL.Query.ExpressionVisitors.NpgsqlSqlTranslatingExpressionVisitor.VisitLikeAnyAll(SubQueryExpression expression) at Npgsql.EntityFrameworkCore.PostgreSQL.Query.ExpressionVisitors.NpgsqlSqlTranslatingExpressionVisitor .VisitSubQuery(SubQueryExpression expression) at Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.SqlTranslatingExpressionVisitor.Visit(Expression expression) at Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.SqlTranslatingExpressionVisitor.VisitBinary(BinaryExpression expression) at Npgsql.EntityFrameworkCore.PostgreSQL.Query.ExpressionVisitors.NpgsqlSqlTranslatingExpressionVisitor .VisitBinary（BinaryExpression 表达式）在 Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.SqlTranslatingExpressionVisitor.Visit（表达式）在 Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.SqlT ranslatingExpressionVisitor.VisitBinary(BinaryExpression expression) at Npgsql.EntityFrameworkCore.PostgreSQL.Query.ExpressionVisitors.NpgsqlSqlTranslatingExpressionVisitor.VisitBinary(BinaryExpression expression) at Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.SqlTranslatingExpressionVisitor.Visit(Expression expression) at Microsoft.EntityFrameworkCore.Query.ExpressionVisitors. SqlTranslatingExpressionVisitor.VisitBinary(BinaryExpression expression) at Npgsql.EntityFrameworkCore.PostgreSQL.Query.ExpressionVisitors.NpgsqlSqlTranslatingExpressionVisitor.VisitBinary(BinaryExpression expression) at Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.SqlTranslatingExpressionVisitor.Visit(Expression expression) at Microsoft.EntityFrameworkCore.Query.RelationalQueryModelVisitor.在 Remotion.Linq.QueryModelVisitorBase.VisitBodyClauses（ObservableCollection 1 bodyClauses, QueryModel queryModel) at Remotion.Linq.QueryModelVisitorBase.VisitQueryModel(QueryModel queryModel) at Microsoft.EntityFrameworkCore.Query.EntityQueryModelVisitor.VisitQueryModel(QueryModel queryModel) at Microsoft.EntityFrameworkCore.Query.RelationalQueryModelVisitor.VisitQueryModel(QueryModel queryModel) at Microsoft.EntityFrameworkCore.Query.EntityQueryModelVisitor.CreateAsyncQueryExecutor[TResult](QueryModel queryModel) at Microsoft.EntityFrameworkCore.Storage.Database.CompileAsyncQuery[TResult](QueryModel queryModel) at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.CompileAsyncQueryCore[TResult](Expression query, IQueryModelGenerator queryModelGenerator, IDatabase database) at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.<>c__DisplayClass22_0 1 bodyClauses, QueryModel queryModel) at Remotion.Linq.QueryModelVisitorBase.VisitQueryModel(QueryModel queryModel) at Microsoft.EntityFrameworkCore.Query.EntityQueryModelVisitor.VisitQueryModel(QueryModel queryModel) at Microsoft.EntityFrameworkCore.Query.RelationalQueryModelVisitor.VisitQueryModel(QueryModel queryModel) at Microsoft.EntityFrameworkCore.Query.EntityQueryModelVisitor.CreateAsyncQueryExecutor[TResult](QueryModel queryModel) at Microsoft.EntityFrameworkCore.Storage.Database.CompileAsyncQuery[TResult](QueryModel queryModel) at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.CompileAsyncQueryCore[TResult](Expression query, IQueryModelGenerator queryModelGenerator, IDatabase database) at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.<>c__DisplayClass22_0 1.b__0() 在 Microsoft.EntityFrameworkCore.Query.Internal.CompiledQueryCache.GetOrAddQueryCore[TFunc]（对象 cacheKey，Func 1 compiler) at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.ExecuteAsync[TResult](Expression query) at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryable 压力1 compiler) at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.ExecuteAsync[TResult](Expression query) at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryable 1.System.Collections.Generic.IAsyncEnumerable.GetEnumerator() 在 System.Linq.AsyncEnumerable.Aggregate_[TSource,TAccumulate,TResult](IAsyncEnumerable 1 source, TAccumulate seed, Func 3 累加器，Func`2 resultSelector，CancellationToken cancellationToken) 在 D:\a\1\s\Ix.NET\Source\System.Interactive.Async\Aggregate.cs:line 118 at {my project}

Answer 1

无法得到与您相同的错误（只是翻译失败，所以如果您可以添加最小的可重现示例会很棒），因为我使用EF.Functions.ILike （带有最新的 npgsql 包）：

List<string> list = new() {"a%", "b%"};
var result = ctx.Apples
    .Where(c => list.Any(xx => EF.Functions.ILike(c.Sort.Name, xx)))
    .ToList();

据我所知，目前还没有实现对本地集合使用StartsWith的支持（基于这个 PR和这个评论），只有EF.Functions.Like和EF.Functions.ILike 。

Answer 2

如果您愿意使用LINQKit ，那么您可以创建扩展方法来从本地 collections 构建表达式：

// searchTerms - IEnumerable<TSearch> where one must match for a row
// testFne(row,searchTerm) - test one of searchTerms against a row
// r => searchTerms.Any(s => testFne(r,s))
public static Expression<Func<T, bool>> AnyIs<T, TSearch>(this IEnumerable<TSearch> searchTerms, Expression<Func<T, TSearch, bool>> testFne) {
    var pred = PredicateBuilder.New<T>();
    foreach (var s in searchTerms)
        pred = pred.Or(r => testFne.Invoke(r, s));

    return pred;
}

// searchTerms - IEnumerable<TSearch> where one must match for a row
// testFne(row,searchTerm) - test one of searchTerms against a row
// dbq.Where(r => searchTerms.Any(s => testFne(r,s)))
public static IQueryable<T> WhereAny<T,TSearch>(this IQueryable<T> dbq, IEnumerable<TSearch> searchTerms, Expression<Func<T, TSearch, bool>> testFne) =>
    dbq.AsExpandable().Where(searchTerms.AnyIs(testFne));

然后您可以将它们用于您的查询：

List<string> list = {...}

apples = apples.WhereAny(list, (a,s) => a.Sort.Name.StartsWith(s));

当然，您也可以创建自己的迷你 LINQKit 来完成相同的任务（尽管它不是那么迷你）。