Mongodb C# Driver Unsupported filter error with specific linq predicate

Question

I have a IMongoCollection of contents:

collection = [
{Value = 'x', EntryPoint= 'ROOT/1' }, 
{Value = 'y', EntryPoint= 'ROOT/2' }, 
{Value = 'z', EntryPoint= 'OTHER/1' }]

now I want to filter my collections with userEntryPoints = ['ROOT', 'SPECIAL'].

We defined, if I have entrypoint = 'ROOT', it is equivalant that we have entrypoint of 'ROOT/1', 'ROOT2' too.

So the expected result is

result = [
{Value = 'x', EntryPoint= 'ROOT/1' }, 
{Value = 'y', EntryPoint= 'ROOT/2' }]

The code I am using is

var collection = mongoDatabase.GetCollection(Data);
return collection.AsQueryable().Select(xxx)
.Where(item => userEntryPoints.Any( entrypoint => item.EntryPoint.StartsWith(entrypoint)))

This should work if collection and userEntryPoints are simple array.

But in my code, at runtime I have a mongodb error:

Unsupported filter: Any(value(System.Collections.Generic.List`1[System.String]].Where({document}{EntryPoint}.StarsWith(document))))

At MongoDB.Driver.Linq.Traslators.PredicateTranslator.Translate(Expression node)

What can I do to make such filtering possible? Thank you.

prasad_ · Accepted Answer · 2021-04-15 19:26:14Z

2

This worked to return the two matching documents:

Regex regex = new Regex("^ROOT|^SPECIAL");
var qry = collection.AsQueryable()
                    .Where<CollectonClass>(e => regex.IsMatch(e.EntryPoint))
                    .Select(e => new { e.Value, e.EntryPoint } );

var docList = qry.ToList();
docList.ForEach(e => Console.WriteLine(e.ToJson()));

A variation:

var rgxList = new string [] { "^ROOT", "^SPECIAL" };
var rgx = new Regex(string.Join("|", rgxList));
var filter = Builders<BsonDocument>.Filter.Regex("EntryPoint", rgx);
var list = collection.Find(filter).ToList<BsonDocument>();

edited Apr 15, 2021 at 19:26

answered Apr 15, 2021 at 18:19

prasad_

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1 Comment

Dĵ ΝιΓΞΗΛψΚ Over a year ago

good one with the or regex. didn't know the driver could translate that. cheers mate!

Dĵ ΝιΓΞΗΛψΚ · Accepted Answer · 2021-04-15 14:37:43Z

1

you can't do that with the driver. it doesn't translate the StartsWith. it would only work with a simple equality check. here's how to get the result you want. you need to convert your input to an array of prefixed regexes. unfortunately there's no strongly typed way to do it.

var userEntryPoints = "[/^ROOT/,/^SPECIAL/]";

FilterDefinition<Content> filter = $"{{ EntryPoint : {{ $in : {userEntryPoints} }} }}";

var result = await (await collection.FindAsync(filter)).ToListAsync();

answered Apr 15, 2021 at 14:37

Dĵ ΝιΓΞΗΛψΚ

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