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C#实体框架复杂连接

left-join join linq entity-framework c#

2

Bhavesh · 技术社区 · 8 年前

从过去5个小时以来一直在努力解决这个问题,但找不到任何解决方案。

基本上,我正在尝试从下面的数据创建一个带有ExcelPackage的excel

Table1
    ID    Name
    1      t1_1
    2      t1_2


Table2
    ID    Name
    1      t2_1
    2      t2_2


Table12
    ID    Table1   Table2   Value
    1      1         1       v11
    2      2         2       v12

从中尝试获得以下任何一项

Table1Name, t2_1, t2_2
t1_1,       v11 ,
t1_2,           , v12

谢谢

1 回复 | 直到 8 年前

1

2

Slava Utesinov 8 年前

var info = (from t1 in Table1                
            from t2 in Table2
            join t120 in Table12 
            on new {Table1 = t1.ID, Table2 = t2.ID} equals new {t120.Table1, t120.Table2} into t12s
            from t12 in t12s.DefaultIfEmpty()
            group new { t2, t12 } by new { t1.ID, t1.Name } into sub
            select new 
            {
                sub.Key.Name,
                data = sub.Select(x => new { x.t2.Name, x.t12 == null ? null : x.t12.Value }).ToList()
            }).ToList();

foreach(var item in info)
{
    Console.Write($"{item.Name}\t");
    foreach(sub in item.data.OrderBy(x => x.Name))
        Console.Write($"{sub.Name}:{sub.Value}\t");
    Console.WriteLine("");
}