I have a telephone number (string) which is "98574524521322". I need to know which country this telephone number belongs to by looking at the country code.
I have 2 tables which are TelephoneMerchant and TelephoneCode.
Note: One telephone merchant can have multiple Telephone Codes.
Note: The first 2 or 4 digits in the telephone number is the telephone Code, found in the TelephoneCodes table.
Question: I want to write a LINQ query to check who the telephone merchant is for the telephone number "98574524521322" ?
My workings:
_dbContext.TelephoneCodes.Where(c => c.Code.ToString().StartsWith("")).FirstOrDefault(c=> c.MerchantName);
The above query doesn't work as I am not sure how to use StartsWith (Or if StartsWith is the right method to use).
The files are given below. Can someone help me how to resolve this ?
public class TelephoneCode: Entity
{
public int Code { get; set; }
public int TelephoneMerchantId { get; set; }
public TelephoneMerchant? TelephoneMerchant{ get; set; }
}
public class TelephoneMerchant: Entity
{
public string? MerchantName { get; set; }
public ICollection<TelephoneCode> TelephoneCodes { get; set; }
}
How the tables look like
Id TelephoneMerchant MerchantName
===================================
1 ABC ABCMErchant
2 BBB BBB MErcrchat
Id Code TelephoneMerchantId
==================================
1 10 1
2 98 1
3 1023 2
This should work:
string phoneNumber = "98574524521322";
IEnumerable<string> matchingMerchants = _dbContext.TelephoneCodes
.Where(c => phoneNumber.StartsWith(c.Code.ToString()))
.Select(c=> c.TelephoneMerchant?.MerchantName)
.ToList();
Now you have all in a list. If you really just want a single, you can also use:
string matchingMerchant = _dbContext.TelephoneCodes
.FirstOrDefault(c => phoneNumber.StartsWith(c.Code.ToString())?.TelephoneMerchant?.MerchantName;
But i would really save Code in a String.