对bool类型查询结果用三元表达式隐射时的一个小问题

[sy-ing]

State = a.State == null ? false : (bool)a.State 这么写是正确的
State = a.State == null ? false : Convert.ToBoolean(a.State), 这样写生成语句报错

[luoyunchong]

什么数据库，我用mysql，第一种写反而是错误的。

[sy-ing]

sqlserver

[2881099]

Convert.ToBoolean 解析时会翻译成 cast ( xx as

[luoyunchong]

sql server local db test

 var testDto11 = select.LeftJoin(a => a.Type.Guid == a.TypeGuid).Limit(10).ToList(a => new TestDto
            {
                id = a.Id,
                name = a.Title,
                State = a.State == null ? false : (Boolean)a.State
            });

这是正常的

 SELECT TOP 10 a__Type.[ParentId] as1, a.[Id] as2, a.[Title] as3, (case when a.[State]  IS  NULL then 0 else a.[State] end) as4 
FROM [tb_topic22] a 
LEFT JOIN [TestTypeInfo] a__Type ON a__Type.[Guid] = a.[TypeGuid]

换成Convert.ToBoolean(a.State)

       var testDto12 = select.LeftJoin(a => a.Type.Guid == a.TypeGuid).Limit(10).ToList(a => new TestDto
            {
                id = a.Id,
                name = a.Title,
                State = a.State == null ? false : Convert.ToBoolean(a.State)
            });

生成的sql多了not in 报错 Incorrect syntax near the keyword 'not'.

SELECT TOP 10 a__Type.[ParentId] as1, a.[Id] as2, a.[Title] as3, (case when a.[State]  IS  NULL then 0 else (cast(a.[State] as varchar) not in ('0','false')) end) as4 
FROM [tb_topic22] a 
LEFT JOIN [TestTypeInfo] a__Type ON a__Type.[Guid] = a.[TypeGuid]

https://github.com/dotnetcore/FreeSql/blob/master/Providers/FreeSql.Provider.SqlServer/SqlServerExpression.cs#L32

在sql server 中，应该是else 不支持 表达式？

[2881099]

是的，顾此失彼

[sy-ing]

在sqlserver下
Enable2 = i.Enable == null ? "0" : Convert.ToBoolean(i.Enable) == true ? "1" : "0",//正确
Enable2 = (bool)i.Enable == true ? "1" : "0",//错误
和上面作为结果不同 作为条件 反而需要Convert.ToBoolean