EF Core one-to-one relationship with string property as key

Question

I am using entity framework core 5 query syntax. There are 3 classes which reflect the tables in database.

public class Record { public int RecordID {get; set;} public decimal Amount {get; set} public string AccountName {get; set;} }

public class Dimension { public int DimensionID {get; set;} public string DimensionSymbol {get; set;} } 
public class DimensionName { public int ID {get; set;} public string Name {get; set;} }

public class RecordDto { public int ID {get; set;} public string DimensionName {get; set;} }

The aim is to find DimensionName foreach Record. The relationship is as follows. RecordID field is a foreign key for Dimension. So it is easy to find this relationship. The problem is with DimensionName. DimensionID is NOT a foreign key to DimensionName. The logical key is DimensionSymbol which sometimes is a simple text like "200.000B" and sometimes it represents the number like 190. If DimensionSymbol is 190 then this 190 reflects the ID in DimensionName.

My query is as follows.

var query = from r in context.Records
join d in context.Dimensions on r.RecordID equals d.DimensionID
join n in context.DimensionNames on int.Parse(d.DimensionSymbol)\>0 ?                    int.Parse(d.DimensionSymbol) : 0  equals n.ID

select new RecordDto
{
ID = r.RecordID,
DimensionName = n.Name
}

And it doesn't work. Could you please adjust the code so that it works? Maybe I should configure sth in OnConfiguring method.