我有两个自定义对象列表：
List1: Year, Month, ValueA
List2: Year, Month, ValueB
我想得到第二个List，两者合并：
List3: Year, Month, ValueA, ValueB
在LINQ VB.Net中有没有优雅的方法来执行它？
示例：
List1:
2010 - 6 - 2
2010 - 7 - 5
2010 - 10 - 3
List2:
2010 - 7 - 2
2010 - 8 - 1
2010 - 10 - 2
List3 (result):
2010 - 6 - 2 - 0
2010 - 7 - 5 - 2
2010 - 8 - 0 - 1
2010 - 10 - 3 - 2
提前致谢。
解决方案 VB.Net解决方案的翻译：
Dim ListA = From a In List1
Group Join b In List2
On a.Year Equals b.Year And a.Month Equals b.Month Into bGroup = Group
From b In bGroup.DefaultIfEmpty()
Select a.Year, a.Month, a.Value1, Value2 = If(b Is Nothing, 0, b.Value2)
Dim ListB = From b In List2
Group Join a In List1
On b.Year Equals a.Year And b.Month Equals a.Month Into aGroup = Group
From a In aGroup.DefaultIfEmpty()
Select b.Year, b.Month, Value1 = If(a Is Nothing, 0, a.Value1), b.Value2
Dim List3 = ListA.Union(ListB)
答案 0 :(得分：8)
当然，您正在寻找对LINQ中不存在的数据执行 Full Outer Join ，因此我们使用两个联合左外连接伪造它：
var A = from a in List1
join b in List2 on new { a.Year, a.Month } equals new { b.Year, b.Month }
into bgroup
from b in bgroup.DefaultIfEmpty()
select new { a.Year, a.Month, a.ValueA, ValueB = (b == null ? 0 : b.ValueB) };
var B = from b in List2
join a in List1 on new { b.Year, b.Month } equals new { a.Year, a.Month }
into agroup
from a in agroup.DefaultIfEmpty()
select new { b.Year, b.Month, ValueA = (a == null ? 0 : a.ValueA), b.ValueB };
var List3 = A.Union(B);
许多对C＃的道歉，我无法让我的VB.Net示例为我的生活工作。你需要联合两个左外连接来产生正确的答案。我尝试过的代码转换器都没有。
以下是LINQPad扼杀的VB.Net，但我能找到的每个例子都应该是正确的：
Dim A = From a In List1 _
Group Join b In List2 _
On New With { a.Year, a.Month } Equals New With { b.Year, b.Month} _
Into bGroup = Group _
From b In bGroup.DefaultIfEmpty() _
Select a.Year, a.Month, a.ValueA, ValueB = If(b Is Nothing, 0, b.ValueB)
Dim B = From b In List2 _
Group Join a In List1 _
On New With { b.Year, b.Month } Equals New With { a.Year, a.Month} _
Into aGroup = Group _
From a In aGroup.DefaultIfEmpty() _
Select b.Year, b.Month, ValueA = If(a Is Nothing, 0, a.ValueA), b.ValueB
Dim List3 = A.Union(B)
答案 1 :(得分：0)
尝试使用此LINQ扩展
public interface IMerge<out T>
{
IEnumerable<IMergeMatched<T>> Matched();
IEnumerable<IMergeMatched<T>> Matched(Func<T, T, bool> predicate);
IEnumerable<T> NotMatchedBySource();
IEnumerable<T> NotMatchedBySource(Func<T, bool> predicate);
IEnumerable<T> NotMatchedByTarget();
IEnumerable<T> NotMatchedByTarget(Func<T, bool> predicate);
}
public interface IMergeMatched<out T>
{
T Source { get; }
T Target { get; }
}
public static class Enumerable
{
public static IMerge<TSource> Merge<TSource>(this IEnumerable<TSource> source, IEnumerable<TSource> target,
Func<TSource, TSource, bool> predicate)
{
return new Merge<TSource>(source, target, predicate);
}
}
public class Merge<T> : IMerge<T>
{
private readonly Func<T, T, bool> _predicate;
private readonly IEnumerable<T> _source;
private readonly IEnumerable<T> _target;
private IEnumerable<IMergeMatched<T>> _matcheds;
private IEnumerable<T> _notMatchedBySource;
private IEnumerable<T> _notMatchedByTarget;
public Merge(IEnumerable<T> source, IEnumerable<T> taget, Func<T, T, bool> predicate)
{
_source = source;
_target = taget;
_predicate = predicate;
}
public IEnumerable<IMergeMatched<T>> Matched()
{
if (_matcheds == null)
{
Analize();
}
return _matcheds;
}
public IEnumerable<IMergeMatched<T>> Matched(Func<T, T, bool> predicate)
{
return Matched()
.Where(t => predicate.Invoke(t.Source, t.Target))
.ToArray();
}
public IEnumerable<T> NotMatchedBySource()
{
if (_notMatchedBySource == null)
{
Analize();
}
return _notMatchedBySource;
}
public IEnumerable<T> NotMatchedBySource(Func<T, bool> predicate)
{
return NotMatchedBySource()
.Where(predicate)
.ToArray();
}
public IEnumerable<T> NotMatchedByTarget()
{
if (_notMatchedByTarget == null)
{
Analize();
}
return _notMatchedByTarget;
}
public IEnumerable<T> NotMatchedByTarget(Func<T, bool> predicate)
{
return NotMatchedByTarget()
.Where(predicate)
.ToArray();
}
private void Analize()
{
var macheds = new List<MergeMached<T>>();
var notMachedBySource = new List<T>(_source);
var notMachedByTarget = new List<T>(_target);
foreach (var source in _source)
{
foreach (var target in _target)
{
var macth = _predicate.Invoke(source, target);
if (!macth) continue;
macheds.Add(new MergeMached<T>(source, target));
notMachedBySource.Remove(source);
notMachedByTarget.Remove(target);
}
}
_matcheds = macheds.ToArray();
_notMatchedBySource = notMachedBySource.ToArray();
_notMatchedByTarget = notMachedByTarget.ToArray();
}
}
public class MergeMached<T> : IMergeMatched<T>
{
public MergeMached(T source, T target)
{
Source = source;
Target = target;
}
public T Source { get; private set; }
public T Target { get; private set; }
}
Impementation：
var source = new List<CustomObject>
{
new CustomObject
{
Year = 2010,
Month = 6,
Value = 2
},
new CustomObject
{
Year = 2010,
Month = 7,
Value = 5
},
new CustomObject
{
Year = 2010,
Month = 10,
Value = 3
}
};
var target = new List<CustomObject>
{
new CustomObject
{
Year = 2010,
Month = 7,
Value = 2
},
new CustomObject
{
Year = 2010,
Month = 8,
Value = 1
},
new CustomObject
{
Year = 2010,
Month = 10,
Value = 2
}
};
var merge = source.Merge(target, (x, y) => x.Year == y.Year && x.Month == y.Month);
var toUpdate = merge.Matched((x, y) => x.Value != y.Value)
.ToArray();
var inSourceButNotInTarget = merge.NotMatchedBySource();
var inTargetButNotInSource = merge.NotMatchedByTarget();
Console.WriteLine("Objects to Update");
foreach (var mergeMatched in toUpdate)
{
Console.WriteLine("Source[{0} -{1} - {2} - {3}]",
mergeMatched.Source.Year,
mergeMatched.Source.Month,
mergeMatched.Source.Value,
mergeMatched.Target.Value);
}
Console.WriteLine("In source but not in target");
foreach (var customObject in inSourceButNotInTarget)
{
Console.WriteLine("Source[{0} -{1} - {2} - 0]",
customObject.Year,
customObject.Month,
customObject.Value);
}
Console.WriteLine("In target but not in source");
foreach (var customObject in inTargetButNotInSource)
{
Console.WriteLine("Source[{0} -{1} - 0 - {2}]",
customObject.Year,
customObject.Month,
customObject.Value);
}
<强>结果：
要更新的对象
2010 -7 - 5 - 2
2010 -10 - 3 - 2
在源头但不在目标中
2010 -6 - 2 - 0
目标但不在来源中
2010年-8 - 0 - 1