如何实现“ IN”？ Dapper Extensions Predicate的子句？

本文介绍了如何实现“ IN”？ Dapper Extensions Predicate的子句？的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述 我要使用Dapper Extensions谓词替换此查询吗？I want to replace this query using Dapper Extensions Predicate?SELECT * FROM SomeTable WHERE id IN (commaSeparatedListOfIDs) commaSeparatedListOfIDs 是整数的 IEnumerable 。我有什么到目前为止尝试过的What I have tried so far:using (SqlConnection cn = new SqlConnection(_connectionString)){ cn.Open(); var predicate = Predicates.Field<SomeTable>(f => f.Id, Operator.???, commaSeparatedListOfIDs); IEnumerable<SomeTable> list = cn.GetList<SomeTable>(predicate); cn.Close();}我需要一个运算符 Operator.In ，但Dapper Extensions中不存在。I need an operator Operator.In, but it does not exists in Dapper Extensions.我应该如何在Dapper Extensions谓词系统中实现 IN子句？How should I implement "IN" clause with Dapper Extensions Predicate system?推荐答案 解决方案1： 使用 PredicateGroup 与 GroupOperator.Or 是一个解决方案。Using PredicateGroup with GroupOperator.Or is one solution.var predicateGroup = new PredicateGroup { Operator = GroupOperator.Or, Predicates = new List<IPredicate>() };foreach(int thisID in commaSeparatedListOfIDs){ var predicate = Predicates.Field<SomeTable>(f => f.Id, Operator.Eq, thisID); predicateGroup.Predicates.Add(predicate);}IEnumerable<SomeTable> list = cn.GetList<SomeTable>(predicateGroup);请参考此和此链接。 解决方案2： 正如您在答案中提到的那样，此链接，使用FieldPredicate（ Predicates.Field ）和 Operator.Eq ，并传递 IEnumerable 参数也应这样做。As you mentioned in your answer and this link, using FieldPredicate (Predicates.Field) with Operator.Eq, and passing IEnumerable parameter should do the same.var predicate = Predicates.Field<SomeTable>(f => f.Id, Operator.Eq, commaSeparatedListOfIDs);此处 Eq 应该在内部翻译为 IN 子句，根据此源Here Eq should be internally translated to IN clause as per this source code of Dapper Extensions on GitHub.if(Value is IEnumerable && !(Value is string)){ if(Operator != Operator.Eq) { throw new ArgumentException("Operator must be set to Eq for Enumerable types"); } List<string> @params = new List<string>(); foreach(var value in (IEnumerable)Value) { string valueParameterName = parameters.SetParameterName(this.PropertyName, value, sqlGenerator.Configuration.Dialect.ParameterPrefix); @params.Add(valueParameterName); } string paramStrings = @params.Aggregate(new StringBuilder(), (sb, s) => sb.Append((sb.Length != 0 ? ", " : string.Empty) + s), sb => sb.ToString()); return string.Format("({0} {1}IN ({2}))", columnName, Not ? "NOT " : string.Empty, paramStrings);} 打开 IN 子句中的 NOT IN 子句，使用最后一个 bool not 参数。有关更多详细信息，请参考此答案。 示例代码如下：To turn the IN clause as mentioned above to NOT IN clause, use the last bool not parameter. Please refer to this answer for more details.Sample code is as below:var predicate = Predicates.Field<Customer>(f => f.CustomerID, Operator.Eq, commaSeparatedListOfIDs, true); 这篇关于如何实现“ IN”？ Dapper Extensions Predicate的子句？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！