I have a list AllIDs:
List<IAddress> AllIDs = new List<IAddress>();
I want to do substring operation on a member field AddressId based on a character "_".
I am using below LINQ query but getting compilation error:
AllIDs= AllIDs.Where(s => s.AddressId.Length >= s.AddressId.IndexOf("_"))
.Select(s => s.AddressId.Substring(s.AddressId.IndexOf("_")))
.ToList();
Error:
Cannot implicitly convert type 'System.Collections.Generic.List<string>' to 'System.Collections.Generic.List<MyCompany.Common.Users.IAddress>'
AllIDs is a list of IAddress but you are selecting a string. The compiler is complaining it cannot convert a List<string> to a List<IAddress>. Did you mean the following instead?
var substrings = AllIDs.Where(...).Select(...).ToList();
If you want to put them back into Address objects (assuming you have an Address class in addition to your IAddress interface), you can do something like this (assuming the constructor for Address is in place):
AllIDs = AllIDs.Where(...).Select(new Address(s.AddressID.Substring(s.AddressID.IndexOf("_")))).ToList();
You should also look at using query syntax for LINQ instead of method syntax, it can clean up and improve the readability of a lot of queries like this. Your original (unmodified) query is roughly equivalent to this:
var substrings = from a in AllIDs
let id = a.AddressId
let idx = id.IndexOf("_")
where id.Length >= idx
select id.Substring(idx);
Though this is really just a style thing, and this compiles to the same thing as the original. One slight difference is that you only have to call String.IndexOf() one per entry, instead of twice per entry. let is your friend.
Maybe this?
var boundable =
from s id in AllIDs
where s.AddressId.Length >= s.AddressId.IndexOf("_")
select new { AddressId = s.AddressId.Substring(s.AddressId.IndexOf("_")) };
boundable = boundable.ToList();
Related
Is it possible to use the aql string handler in ArangoDB to perform a dynamic query? I've tried a number of different ways but it always errors out. For example, I'd like to do something like this:
let sortExpression = sortByDate ? 'SORT ${date}' : `SORT ${name}`
const result = db._query(aql`
FOR doc IN tickets
${sortExpression}
RETURN doc
`)
This example is very simplified, but I have a more complex situation where something like this would be really handy. Is there a way to make something like this work?
If the query was more complex, and I had real variables to embed, I'd write this like the following:
let sortProp = sortByDate ? 'date' : 'name';
var query = aql`
FOR doc IN tickets
SORT #SORT_PROP#
RETURN doc`;
query.query = query.query.replace('#SORT_PROP#', sortProp);
var result = db._query(query);
Maybe this works for your use case, too.
After looking more closely at how the aql string handler works, it turns out what I'm trying to do is just not feasible with it. So I decided to use the regular bind var syntax:
let sortExpression = 'SORT #sortField'
const result = db._query(`
FOR doc IN ##coll
${sortExpression}
RETURN doc
`, {
'#coll': module.context.collectionName('tickets'),
'sortField': sortByDate ? 'date' : 'name'
})
Again this is overkill for the simple example above, but my real world query is much more complex.
Having seen this question I'm not sure why the following code for my DocDb instance isn't working:
var userApps = _docs.CreateDocumentQuery(UriFactory.CreateDocumentCollectionUri(Constants.Databases.Applications.ID, Constants.Databases.Applications.Collections.USER_APPS),
new SqlQuerySpec(#"SELECT r.appId FROM ROOT r WHERE r.userId = #userId", (#"#userId", userId).ToSqlParameters()))
.ToList()
.Select(s => (string)s.appId);
var query = _docs.CreateDocumentQuery<Document>(UriFactory.CreateDocumentCollectionUri(Constants.Databases.Applications.ID, Constants.Databases.Applications.Collections.APP_DEFINITIONS),
new SqlQuerySpec(#"SELECT r.id, r.appName FROM ROOT r WHERE r.appId IN (#userApps)", (#"#userApps", userApps.ToArray()).ToSqlParameters()),
new FeedOptions { EnableCrossPartitionQuery = true })
.AsDocumentQuery();
When I execute this, though I know the data should be returning me back a result set, it comes back empty every time.
Troubleshooting so far
Variants of .Select()
Return strings that I string.Join in to a comma-separated list.
Eg:
var userApps = string.Join(#",", _docs.CreateDocumentQuery(UriFactory.CreateDocumentCollectionUri(Constants.Databases.Applications.ID, Constants.Databases.Applications.Collections.USER_APPS),
new SqlQuerySpec(#"SELECT r.appId FROM ROOT r WHERE r.userId = #userId", (#"#userId", userId).ToSqlParameters()))
.ToList()
.Select(s => $#"'{s.appId}'");
Don't encapsulate IN parameter
Removing the () around the parameter spec in the query thinking maybe the SqlParameter spec was doing the array specification?
Eg: #"SELECT r.id, r.appName FROM ROOT r WHERE r.appId IN #userApps")
Ends up throwing "Syntax error, incorrect syntax near '#userApps'."
Validate via Azure Portal queries
Ran the (expected) SQL that this code should be running.
I get back my expected results without issue (ie: I know there is a result set for these queries as-written).
Debugger output for Query 1
AppIds are coming back from query 1.
Unsatisfactory workaround
Change query 2 to not be parameterized. Rather, inject the comma-separated list of IDs from query 1 in to it:
var userApps = string.Join(#",", _docs.CreateDocumentQuery(UriFactory.CreateDocumentCollectionUri(Constants.Databases.Applications.ID, Constants.Databases.Applications.Collections.USER_APPS),
new SqlQuerySpec(#"SELECT r.appId FROM ROOT r WHERE r.userId = #userId", (#"#userId", userId).ToSqlParameter()))
.ToList()
.Select(s => $#"'{s.appId}'"));
var query = _docs.CreateDocumentQuery<Document>(UriFactory.CreateDocumentCollectionUri(Constants.Databases.Applications.ID, Constants.Databases.Applications.Collections.APP_DEFINITIONS),
new SqlQuerySpec($#"SELECT r.id, r.appName FROM ROOT r WHERE r.appId IN ({userApps})"),
new FeedOptions { EnableCrossPartitionQuery = true })
.AsDocumentQuery();
Works perfectly but I'm not going to accept it as an answer to this problem as it goes against a couple decades-worth of SQL best practices and, frankly, shouldn't be a solution.
Here's my ToSqlParameters() extension method in case it's the culprit (this works everywhere else I've used it, though. Maybe something special is needed for arrays?):
public static SqlParameterCollection ToSqlParameters(this (string, object) parmDef) => new SqlParameterCollection(new[] { new SqlParameter(parmDef.Item1, parmDef.Item2) });
Thanks!
If you use a parameterized IN list, then it will be considered as a single value when the parameter is expanded.
For instance, for this query:
SELECT * FROM r WHERE r.item IN (#items) And #items is defined as "['val1', 'val2', 'val3']" will be interpreted as such:
SELECT * FROM r WHERE r.item IN (['val1', 'val2', 'val3'])
which basically means that you're comparing r.item to a single value that is an array of three elements (i.e. equivalent to r.item = ['val1', 'val2', 'val3']).
To compare to multiple items, you need to use a parameter for each value. Something like this: SELECT * FROM r WHERE r.item IN (#val1, #val2, #val3])
A more convenient way to write this query is to use ARRAY_CONTAINS instead and pass the array of items as a single parameter. So the above query will be written like this:
SELECT * FROM r WHERE ARRAY_CONTAINS(#items, r.item)
I am trying to use a string ('npcName') as a variable name. So far I have tried casting dialogMap into a DynamicAccess object, but it gives me the error 'Invalid array access' when I try this:
var npcName:String = 'TestNPC';
var casted = (cast Registry.dialogMap:haxe.DynamicAccess<Dynamic>);
var tempname = casted[root.npcName[0].message];
trace(tempname);
'dialogMap' is an empty map which I want to fill like so:
Registry.dialogMap['message'] = root.npcName[0].message;
How can I use npcName, a string, in the above line of code? Is there a way to transform the string into something usable? Any help would be appreciated.
The haxe.DynamicAccess doesn't have array access (like map[key]), but is an abstract type for working with anonymous structures that are intended to hold collections of objects by the string key. It is designed to work with map.get(key) and map.set(key). It is basically a nicer wrapper around Reflect.field and Reflect.setField and does some safety checks with Reflect.hasField.
var variable = "my_key";
var value = 123;
var dynamicMap = new haxe.DynamicAccess<Dynamic>();
dynamicMap.set(variable, value);
I'm noticing you are doing very much cast and dynamic, so untyped code, which is a bit of contradiction in a typed language. What is the actual type of dialogMap?
Not sure you are aware of it but, Haxe has its own maps, which are fully typed, so you don't need casts.
var map = new Map<String, Int>();
map[variable] = value;
I think this article helps understanding how to work with dynamic (untyped) objects.
Tip; for testing such small functionalities you can doodle around on the try.haxe site : http://try.haxe.org/#4B84E
Hope this helps, otherwise here is some relevant documentation:
http://api.haxe.org/haxe/DynamicAccess.html
https://haxe.org/manual/std-reflection.html
https://haxe.org/manual/types-dynamic.html
http://code.haxe.org/category/beginner/string-variable-reflection.html
I have the following c# code:
private XElement BuildXmlBlob(string id, Part part, out int counter)
{
// return some unique xml particular to the parameters passed
// remember to increment the counter also before returning.
}
Which is called by:
var counter = 0;
result.AddRange(from rec in listOfRecordings
from par in rec.Parts
let id = GetId("mods", rec.CKey + par.UniqueId)
select BuildXmlBlob(id, par, counter));
Above code samples are symbolic of what I am trying to achieve.
According to the Eric Lippert, the out keyword and linq does not mix. OK fair enough but can someone help me refactor the above so it does work? A colleague at work mentioned accumulator and aggregate functions but I am novice to Linq and my google searches were bearing any real fruit so I thought I would ask here :).
To Clarify:
I am counting the number of parts I might have which could be any number of them each time the code is called. So every time the BuildXmlBlob() method is called, the resulting xml produced will have a unique element in there denoting the 'partNumber'.
So if the counter is currently on 7, that means we are processing 7th part so far!! That means XML returned from BuildXmlBlob() will have the counter value embedded in there somewhere. That's why I need it somehow to be passed and incremented every time the BuildXmlBlob() is called per run through.
If you want to keep this purely in LINQ and you need to maintain a running count for use within your queries, the cleanest way to do so would be to make use of the Select() overloads that includes the index in the query to get the current index.
In this case, it would be cleaner to do a query which collects the inputs first, then use the overload to do the projection.
var inputs =
from recording in listOfRecordings
from part in recording.Parts
select new
{
Id = GetId("mods", recording.CKey + part.UniqueId),
Part = part,
};
result.AddRange(inputs.Select((x, i) => BuildXmlBlob(x.Id, x.Part, i)));
Then you wouldn't need to use the out/ref parameter.
XElement BuildXmlBlob(string id, Part part, int counter)
{
// implementation
}
Below is what I managed to figure out on my own:.
result.AddRange(listOfRecordings.SelectMany(rec => rec.Parts, (rec, par) => new {rec, par})
.Select(#t => new
{
#t,
Id = GetStructMapItemId("mods", #t.rec.CKey + #t.par.UniqueId)
})
.Select((#t, i) => BuildPartsDmdSec(#t.Id, #t.#t.par, i)));
I used resharper to convert it into a method chain which constructed the basics for what I needed and then i simply tacked on the select statement right at the end.
Is it possible to load objects by a list of ids using subsonic ActiveRecord?
My code looks like:
IList<Video> videos = Video.Find(v => videoIds.Contains(v.ID));
I get an exception: The method 'Contains' is not supported
Do I do something wrong ... or I hit one of subsonic's limitations?
Thanks, Radu
After more research I found a way to achieve this:
List<int> videoIds = new List<int>(){1, 2, 3, 4, 5};
SqlQuery query = new Select().From<Video>().Where("ID").In(videoIds);
List<Video> videos = query.ExecuteTypedList<Video>();
FYI: SubSonic's linq parser does not like generic Lists and Contains
// does not work
List<int> videoIds = new List<int>() {1,2,3,4,5};
var videos = Video.Find(v => videoIds.Contains(v.ID));
// should work
IEnumerable<int> videoIds = new List<int>() {1,2,3,4,5};
var videos = Video.Find(v => videoIds.Contains(v.ID));
Noticed the difference?
Sounds strange, but whenever you want to use Contains() with Subsonic, you first have to cast your List to an IEnumerable to prevent the NotSupportedException.
This is the one-liner I believe you where looking for.
var colMatchingVideos = Video.Find( objVideo => colVideoIds.Any( iVideoId => objVideo.ID == iVideoId).ToList();
Also I would strongly advise you avoid using string literals for columns, instead you could use Video.Columns.Id or expressions Where( o => o.Id). This would ensure that if you change your column names in the Database a compile time exception will occur. Help's a lot with maintainability.