Suppose I have this simple object definition:
public class Item
{
public int section { get; set; }
public string item { get; set; }
}
I have some data in a single-depth array. This is JSON, which would be converted to C# objects via Json.NET:
[
{
"section": 0,
"item": "Hello!"
},
{
"section": 1,
"item": "First Steps"
},
{
"section": 1,
"item": "How to Ask for Help"
},
{
"section": 2,
"item": "Your First Program"
},
{
"section": 2,
"item": "The Code"
},
{
"section": 2,
"item": "How It Works"
},
{
"section": 3,
"item": "Where To Go From Here"
}
]
Using Entity Framework or some other method, I have arrived at a simple list of these objects as stated above, contained within a var variable.
Now what I want to do is get the same list, but where each section is grouped as an array within the outer array. For example, the JSON of what I want looks like this:
[
[
{
"section": 0,
"item": "Hello!"
}
],
[
{
"section": 1,
"item": "First Steps"
},
{
"section": 1,
"item": "How to Ask for Help"
}
],
[
{
"section": 2,
"item": "Your First Program"
},
{
"section": 2,
"item": "The Code"
},
{
"section": 2,
"item": "How It Works"
}
],
[
{
"section": 3,
"item": "Where To Go From Here"
}
]
]
My initial thought was to do something with a LINQ query using the groupby statement but I don't think this is what I'm looking for - groupby seems to be analogous to the SQL version so it can only be used for aggregate operations.
The only other option I have found so far is to use a LINQ query to get a list of all of the sections:
var allSections = (from x in myData select x.section).Distinct();
...and then iterate through those IDs and manually build the array:
List<List<Item>> mainList = new List<List<Item>>();
foreach (int thisSection in allSections.ToArray())
{
List<Item> thisSectionsItems = (from x in myData where x.section == thisSection select x).ToList();
mainList.Add(thisSectionsItems);
}
return mainList;
This should result in a proper enumerable that I can feed into JSON.NET and get the expected result, but this seems inefficient.
Is there a more LINQ-ish, or at least more efficient, way to split the items into groups?
You can certainly achieve this with .GroupBy()
var grouped = items
.GroupBy(x => x.section) // group by section
.Select(x => x.ToArray()) // build the inner arrays
.ToArray(); // return collection of arrays as an array
Related
"hits" : [
{
"id": 1,
"sampleArrayData": ["x"]
},
{
"id": 2,
"sampleArrayData": ["y"]
},
{
"id": 3,
"sampleArrayData": ["z"]
},
{
"id": 4,
"sampleArrayData": ["x", "y", "z"]
},
{
"id": 5,
"sampleArrayData": ["z", "w"]
}
]
It's a sample data of index.
I want to search this index by sampleArrayData field which includes one or more values I will give dynamically.
For example if want to search this index by ["x","y"] parameters. I must get data which includes "x", or "y" or both "x", "y". (First three records from this index).
We could do this by using terms query on the old elastic search versions like below.
{
"query": {
"bool": {
"must": [
{
"terms": {
"sampleArrayData": [ "x", "y"]
}
}
]
}
}
}
But we can not use terms query for "text" or "keyword" type fields on the elasticsearch current versions.
How can I dynamically search this index with unknown number of parameters on the C# NEST library?
There is an entity with custom fields that can change their value. The fields are stored as an array.
public class SomeEntity :...
{
...
public List<CustomField> FieldList { get; set; } = new List<CustomField>();
...
}
I use code like this to update one field:
var filterBuilder = Builders<SomeEntity>.Filter;
var updateFilter =
filterBuilder.Eq(e => e.EntityId, entityToUpdate.EntityId)
& filterBuilder.ElemMatch(e => e.FieldList, f => f.FieldId == updateField.FieldId);
var updateDef = Builders<SomeEntity>.Update.Set(e => e.FieldList[-1].Value, updateField.Value);
var updateRes = await GetEntityCollection().UpdateOneAsync(updateFilter, updateDef);
Sometimes it becomes necessary to update the values of several fields in the database at the same time, but I cannot find a way to do this in one action.
Is it possible in MongoDB to first search for a document using a filter, and then update/delete several elements of its array by their Id's (changes for each element may be different) in one action?
Is it possible to do the same for several documents (for example, remove fields with certain identifiers from all objects matching the filter)?
An example of an object before the change:
{
...
"fieldList": [
{
"id": "3bf2c235-82c3-40e4-91dc-46dc4c1ed177",
"type": 0,
"value": 10
},
{
"id": "5909dabd-fe8f-4edb-a642-c052e23082d8",
"type": 1,
"value": "some value"
},
{
"id": "66805403-d508-4b99-82f3-fa2ed828c19e",
"type": 3,
"value": "2019-08-01T12:00:00"
}
]
}
An example of an object after modification (only one document is updated):
{
...
"fieldList": [
{
"id": "3bf2c235-82c3-40e4-91dc-46dc4c1ed177",
"type": 0,
"value": 500
},
{
"id": "5909dabd-fe8f-4edb-a642-c052e23082d8",
"type": 1,
"value": "new value"
},
{
"id": "66805403-d508-4b99-82f3-fa2ed828c19e",
"type": 3,
"value": "2020-09-10T10:00:00"
}
]
}
An example of an object after a massive change (the document matched the filter, by analogy, all documents that would fit the filter should be updated - delete two fields, add a default value for some field):
{
...
"fieldList": [
{
"id": "3bf2c235-82c3-40e4-91dc-46dc4c1ed177",
"type": 0,
"value": 500,
"defaultValue": 150
}
]
}
starting from a JObject I can get the array that interests me:
JArray partial = (JArray)rssAlbumMetadata["tracks"]["items"];
First question: "partial" contains a lot of attributes I'm not interested on.
How can I get only what I need?
Second question: once succeeded in the first task I'll get a JArray of duplicated items. How can I get only the unique ones ?
The result should be something like
{
'composer': [
{
'id': '51523',
'name': 'Modest Mussorgsky'
},
{
'id': '228918',
'name': 'Sergey Prokofiev'
},
]
}
Let me start from something like:
[
{
"id": 32837732,
"composer": {
"id": 245,
"name": "George Gershwin"
},
"title": "Of Thee I Sing: Overture (radio version)"
},
{
"id": 32837735,
"composer": {
"id": 245,
"name": "George Gershwin"
},
"title": "Concerto in F : I. Allegro"
},
{
"id": 32837739,
"composer": {
"id": 245,
"name": "George Gershwin"
},
"title": "Concerto in F : II. Adagio"
}
]
First question:
How can I get only what I need?
There is no magic, you need to read the whole JSON string and then query the object to find what you are looking for. It is not possible to read part of the JSON if that is what you need. You have not provided an example of what the data looks like so not possible to specify how to query.
Second question which I guess is: How to de-duplicate contents of an array of object?
Again, I do not have full view of your objects but this example should be able to show you - using Linq as you requested:
var items = new []{new {id=1, name="ali"}, new {id=2, name="ostad"}, new {id=1, name="ali"}};
var dedup = items.GroupBy(x=> x.id).Select(y => y.First()).ToList();
Console.WriteLine(dedup);
I have three different arrays which I want to merge them into a single object.
array 1 : [{"Id":1,"Number":"1234","Category":"Chocalte", "Status": "Error"}]
heatingissues: [{"myId":3,"Id":"5801"}]
problemissue: [{"myId":1,"Id":2,"Name":"Desktop"}]
I want result to be like this:
{
"Id": 3,
"Number": "1190042293",
"Category": "Chocalte",
"heatingissues": [
{
"myId": 3,
"id": "5801"
}
],
"problemissue": [
{
"myId": 1,
"name": "Desktop"
}
]
}
After deserializing all the arrays individually (respectively to the results and problemissueresults variables) I try:
var j = JsonConvert.SerializeObject(new{
results,
heatingissues= problemissueresults,
problemissue= problemissueresults
});
Which generates the following output:
{
"results": [
{
"id": 3,
"Number": "1190042293",
"category": "Chocalte"
}
],
"heatingissues": [
{
"myId": 3,
"id": "5801"
}
],
"problemissue": [
{
"myId": 1,
"name": "Desktop"
}
]
}
How can I avoid these results?
In this case, you need to declare explicitly the properties of the object you are serializing to match the format you want.
In words of the documentation for C# Anonymous Types:
If you do not specify member names in the anonymous type, the compiler gives the anonymous type members the same name as the property being used to initialize them
So your result was being serialized as an array with a json key of the same name.
Try this:
var obj =
new
{
id = results[0].id,
number = results[0].number,
category = results[0].category,
heatingissues= problemissueresults,
problemissue= problemissueresults
};
var j = JsonConvert.SerializeObject(obj);
Newtonsoft json library support merging operation.
http://www.newtonsoft.com/json/help/html/MergeJson.htm
I have an object that I am converting to JSON to be consumed by Ember.js.
Currently I have some child objects that are fully expanded but ember expects
just an array of ids on the client side. How can I flatten the object out to
be a int[]
items = Mapper.Map<IList<Item>>(client.GetItems());
foreach (var item in items)
{
int[] choices = item.Choices.Select(x => x.Id).ToArray();
item.Choices = choices;
}
get an error about not being able to convert to type int[] from IList<Item>
how can I cast the property?
example current JSON I produce after serializing
{ "items": [
{
"id": 0,
"name": "Item0",
"description": "...",
"choices": [
{ "id": 0, "property": "somevalue" },
{ "id": 1, "property": "somevalue" },
]
},
{
"id": 1,
"name": "Item1",
"description": "...",
"choices": [
{ "id": 0, "property": "somevalue" },
{ "id": 1, "property": "somevalue" },
]
}
]}
The JSON I would like to produce
{ "items": [
{
"id": 0,
"name": "Item0",
"description": "...",
"choices": [0, 1]
},
{
"id": 1,
"name": "Item1",
"description": "...",
"choices": [0, 1]
}
]}
SelectMany flattens List of Lists and produces single List with all items.
items.SelectMany(x=>x.Choices.Select(y=>y.Id).ToArray()));
get an error about not being able to convert to type int[] from IList how can I cast the property?
You cannot cast one type to another. Instead you can create another property of type int[] in your class and use the LINQ statement in getter (with necessary validation checks).
public int[] ChoiceIDs
{
get {
return this.Choices.Select(x => x.Id).ToArray();
}
}