C# 导致指定强制转换的位列的LINQ并集无效错误

我在几个表之间有一个复杂的连接，但我已经使用linqpad和下面的小表成功地复制了错误。COLNAME列和YAXIS列之间以及COLNAME和XAXIS之间存在未明确定义的引用

错误是“指定的强制转换无效”，最初我认为问题是转换VS 2010中返回到我的对象的数据，这浪费了时间，但是错误也发生在没有定义对象的linqpad中。一个bit列会导致这个问题，这似乎很疯狂。如果我将列类型更改为VARCHAR，它就可以正常工作。如果我从linqpad或SQL分析器运行生成的SQL，也会返回fine

发生了什么事

CREATE TABLE TEST_QUERY 
([ID] INT IDENTITY(1,1) PRIMARY KEY,
 blah VARCHAR(20))

CREATE TABLE TEST_QUERY_COLS
(QUERYID INT NOT NULL,
 COLNAME VARCHAR(20) NOT NULL,
 otherblah VARCHAR(20),
 PRIMARY KEY(QUERYID,COLNAME))

CREATE TABLE TEST_CHART
(CHARTID INT IDENTITY(1,1) PRIMARY KEY,
 QUERYID INT NOT NULL REFERENCES TEST_QUERY([ID]),
 XAXIS VARCHAR(20) NOT NULL,
 blahblah VARCHAR(20))

CREATE TABLE TEST_CHART_SERIES
(CHARTID INT NOT NULL REFERENCES TEST_CHART(CHARTID),
 YAXIS VARCHAR(20) NOT NULL,
 blahblahblah BIT NOT NULL,
 PRIMARY KEY(CHARTID,YAXIS))

INSERT INTO TEST_QUERY(blah) VALUES('xxx')
INSERT INTO TEST_QUERY_COLS(QUERYID,COLNAME,otherblah) VALUES(1,'col1','xxx')
INSERT INTO TEST_QUERY_COLS(QUERYID,COLNAME,otherblah) VALUES(1,'col2','yyy')
INSERT INTO TEST_CHART(QUERYID,XAXIS,blahblah) VALUES(1,'col1','xxx')
INSERT INTO TEST_CHART_SERIES(CHARTID,YAXIS,blahblahblah) VALUES(1,'col2',1)

这是linq声明：

((from ch in TEST_CHARTs
join a in TEST_CHART_SERIES on ch.CHARTID equals a.CHARTID into a_join
from cs in a_join.DefaultIfEmpty()
join ycols in TEST_QUERY_COLS on new { key1 = cs.YAXIS, key2 = ch.QUERYID } equals new { key1 = ycols.COLNAME, key2 = ycols.QUERYID }
where ch.CHARTID == 1
select new 
{
    ch.CHARTID,
    POSITION = 0,
    ycols.QUERYID,
    ycols.Otherblah,
    cs.Blahblahblah
})
.Union(from ch in TEST_CHARTs
join xcol in TEST_QUERY_COLS on new { key1 = ch.XAXIS, key2 = ch.QUERYID } equals new { key1 = xcol.COLNAME, key2 = xcol.QUERYID }
where ch.CHARTID == 1
select new 
{
    ch.CHARTID,
    POSITION = 0,
    xcol.QUERYID,
    xcol.Otherblah,
    Blahblahblah = false
})).Distinct()

---

编辑：我向microsoft提交了一个bug

生成的sql包含以下行，其中@p4对应于投影中的

Blahblahblah=false

行：

DECLARE @p4 Int = 0

var one =
    (from ch in TEST_CHARTs
    join a in TEST_CHART_SERIES on ch.CHARTID equals a.CHARTID into a_join
    from cs in a_join.DefaultIfEmpty()
    join ycols in TEST_QUERY_COLS on new { key1 = cs.YAXIS, key2 = ch.QUERYID } equals new { key1 = ycols.COLNAME, key2 = ycols.QUERYID }
    where ch.CHARTID == 1
    select new 
    {
        ch.CHARTID,
        POSITION = 0,
        ycols.QUERYID,
        ycols.Otherblah,
        Blahblahblah = cs.Blahblahblah
    }).ToList();

var two =
    (from ch in TEST_CHARTs
    join xcol in TEST_QUERY_COLS on new { key1 = ch.XAXIS, key2 = ch.QUERYID } equals new { key1 = xcol.COLNAME, key2 = xcol.QUERYID }
    where ch.CHARTID == 1
    select new 
    {
        ch.CHARTID,
        POSITION = 0,
        xcol.QUERYID,
        xcol.Otherblah
    }).ToList();

var three = 
    from x in two
    select new
    {
        x.CHARTID,
        x.POSITION,
        x.QUERYID,
        x.Otherblah,
        Blahblahblah = false
    };

var four = one.Union(three).Distinct();

查询返回的int不能转换为bool。我不知道这是否是一个LINQtoSQL错误（似乎是这样），但有一个解决方法。基本上，您需要从投影的匿名类型中删除

Blahblahblah=false

，然后

.ToList（）

或

.ToArray（）

结果，最后在linq to objects投影中添加bool字段：

DECLARE @p4 Int = 0

var one =
    (from ch in TEST_CHARTs
    join a in TEST_CHART_SERIES on ch.CHARTID equals a.CHARTID into a_join
    from cs in a_join.DefaultIfEmpty()
    join ycols in TEST_QUERY_COLS on new { key1 = cs.YAXIS, key2 = ch.QUERYID } equals new { key1 = ycols.COLNAME, key2 = ycols.QUERYID }
    where ch.CHARTID == 1
    select new 
    {
        ch.CHARTID,
        POSITION = 0,
        ycols.QUERYID,
        ycols.Otherblah,
        Blahblahblah = cs.Blahblahblah
    }).ToList();

var two =
    (from ch in TEST_CHARTs
    join xcol in TEST_QUERY_COLS on new { key1 = ch.XAXIS, key2 = ch.QUERYID } equals new { key1 = xcol.COLNAME, key2 = xcol.QUERYID }
    where ch.CHARTID == 1
    select new 
    {
        ch.CHARTID,
        POSITION = 0,
        xcol.QUERYID,
        xcol.Otherblah
    }).ToList();

var three = 
    from x in two
    select new
    {
        x.CHARTID,
        x.POSITION,
        x.QUERYID,
        x.Otherblah,
        Blahblahblah = false
    };

var four = one.Union(three).Distinct();

请注意，这将导致两个sql查询，而不是一个

编辑

---

另外，Distinct（）可以省略，因为union不包含重复项。我真的应该读我复制粘贴的代码

@Filip:我们公司的标准做法是将所有DB列和表名都用大写字母表示。另外，我总是在sql中大写关键字：）我不记得曾经在LINQtoSQL中使用过bit。。。sql server位是否直接映射到.net布尔值？如果没有，则在尝试合并这两个结果时肯定会出现问题。@jlnorsworthy它将其转换为布尔值。适用于其他位列：）