比较2清单 <Dictionary<string,object> &gt;在C＃中

Question

I have 2 list of dictionaries

List<Dictionary<string,object>> master
List<Dictionary<string,object>> sub

Both my dictionaries have identical Key names.

EX: The first list Master contains
Master.Add(new Dictionary<string, string>(){

{"key1","SAME1"}
{"key2", "value1"},
{"key3","value2"}
});
Master.Add(new Dictionary<string, string>(){
{"key1","SAME2"}
{"key2", "value3"},
{"key3","value5"}
});

Master.Add(new Dictionary<string, string>(){
{"key1","SAME77"}
{"key2", "value55"},
{"key3","value44"}
});

The second list sub contains similar kind of key,value pairing :

sub.Add(new Dictionary<string, string>(){
{"key1","SAME1"}
{"key2", "value7"},
{"key3","value9"}
});

Master.Add(new Dictionary<string, string>(){
{"key1","SAME2"}
{"key2", "value3"},
{"key3","value4"}
});

Is there a way in LinQ(or any other easier way) i can use to compare the 2 list of dictionaries and get an output Dictionary. Example

Scenario 1: As you can see i can use one of the Keys(Key1 since it is the same Value for all) from the first list of dictionaries to see if that Value exists in the second dictionary and if it does not i want the missing dictionary in a new List> .

Output Ex: NewList.Add(new Dictionary<string, string>(){
{"key1","SAME77"} // since SAME77 isn't present in sub dictionary 
{"key2", "value55"},
{"key3","value44"}
}

Scenario 2: If suppose one of the dictionary in the sub list of dictionaries contains the same value for the key1 , I want to check the other values of the same dictionary and if any values for those keys have changed and if they have i want a new List having the original one.

ex output :

NewList.Add(new Dictionary<string, string>(){
{"key1","SAME2"}
{"key2", "value3"},
{"key3","value5"} // since the master dictionary has value5 and the sublist dictionary has value 4 

}

Scenario 1 Attempt:

var result = Master.SelectMany(m=>m).Where(e=>sub.SelectMany(a=>a)
                .Any(p => e.Key == p.Key && p.Value!=null && e.Value!=(p.Value)));

However this does not return the correct result and the output is in IEnumerable. Is there away i can get the required output through linq itself?

Appreciate any help

Answer 1

As a caveat, your data structure is hardly ideal. Since you are treating the first value of the first key as your "key", you might want to consider recreating your structure to use your "SAME1" (and similar values) as the keys.

That said, you can still accomplish both queries in "single-line" LINQ statements.

var masterOnly = Master.Where(m => 
    !sub.Select(s => s.First().Value).Contains(m.First().Value)
).ToList();

In the master only scenario, we use a Where clause to allow us to first build out a collection of sub -> first -> values and we then check each master -> first -> value in our loop against that collection. If the value does not exist, we return the value.

var hasChanged = Master.Where(m => 
    sub.FirstOrDefault(s => 
        s.First().Value == m.First().Value)?.SequenceEqual(m) == false)
    .ToList();

In this scenario, we can take advantage of C#6's null propagation operator to avoid needing to use .ForEach() to build a match in a loop since if the value is null, our SequenceEquals check is ignored.

In the case where we have a match, we want to explicitly compare its sequence against our master collection and if any entry does not match, we return it.