Linq filter builder not accepting lambda for filter type IN-CodePudding

Basically what I'm trying to do is a deleteMany based on a list of items that I have using C# and linq for a mongoDB.

This is my code:

// List of elements to delete, read from the POST request   
string jsonBoletines = await new StreamReader(req.Body).ReadToEndAsync();

// Convert the JSON into a list of "Boletin" objects, which is the type of objects I want //to delete from the collection 
List <Boletin> boletinesToDelete = JsonConvert.DeserializeObject<List<Boletin>>(jsonBoletines);

// Create the filter using IN, I'm trying to delete using the _id
var filter = Builders<Boletin>.Filter.In(item => item._id, boletinesToDelete);

var results = collection.DeleteMany(filter);

My code will not compile because on the lambda inside the IN filter shows this error:

var filter = Builders<Boletin>.Filter.In(item => item._id, boletinesToDelete);

CS1660: Cannot convert lambda expression to type X because it is not a delegate type

Did some research and the error is supposed to be "This error occurs if you try to assign or otherwise convert an anonymous method block to a type which is not a delegate type". But I'm not sure I get it since I'm not that familiar with delegate type

Please help

CodePudding user response：

From memory, I think an intersect may work better for this.

var filter =  Builders<Boletin>.Intersect(boletinesToDelete);

CodePudding user response：

boletinesToDelete should be a List<ObjectId> or a List<string> according to your item._id not a List<Boletin>.

db.collection.find({
  _id: {
    "$in": [
      ObjectId("5a934e000102030405000000"),
      ObjectId("5a934e000102030405000001")
    ]
  }
})

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