问题描述
我有一个包含 nvarchar 列的数据库表,如下所示:
I have a database table that contains an nvarchar column like this:
1|12.6|18|19
我有一个具有 Decimal[] 属性的业务对象.
I have a Business Object that has a Decimal[] property.
我的 LINQ 查询如下所示:
My LINQ Query looks like this:
var temp = from r in db.SomeTable select new BusinessObject { // Other BusinessObject Properties snipped as they are straight 1:1 MeterValues = r.MeterValues.Split('|').Select(Decimal.Parse).ToArray() }; var result = temp.ToArray();
这会引发 NotSupportedException:Method 'System.String[] Split(Char[])' 不支持转换为 SQL.
This throws an NotSupportedException: Method 'System.String[] Split(Char[])' has no supported translation to SQL.
这有点糟糕:) 有什么方法可以做到这一点,而无需向业务对象添加字符串属性或选择匿名类型然后遍历它?
That kinda sucks :) Is there any way I can do this without having to add a string property to the business object or selecting an anonymous type and then iterating through it?
我目前的解决方案"是:
My current "solution" is:
var temp = from r in db.SomeTable select new { mv = r.MeterValues, bo = new BusinessObject { // all the other fields } }; var result = new List<BusinessObject>(); foreach(var t in temp) { var bo = t.bo; bo.MeterValues = t.mv.Split('|').Select(Decimal.Parse).ToArray(); result.Add(bo); } return result.ToArray(); // The Method returns BusinessObject[]
不过,这个临时列表有点难看.
That's kinda ugly though, with that temporary list.
我尝试添加一个 let mv = r.MeterValues.Split('|').Select(Decimal.Parse).ToArray() 但这基本上会导致相同的 NotSupportedException.
I've tried adding a let mv = r.MeterValues.Split('|').Select(Decimal.Parse).ToArray() but that essentially leads to the same NotSupportedException.
如果重要的话,这是 .net 3.5SP1.
This is .net 3.5SP1 if that matters.
推荐答案
您需要先调用 .AsEnumerable() 来强制 select 子句在客户端上运行:
You need to force the select clause to run on the client by calling .AsEnumerable() first:
var result = db.SomeTable.AsEnumerable().Select(r => new BusinessObject { ... MeterValues = r.MeterValues.Split('|').Select(Decimal.Parse).ToArray() }).ToList();