Ef core query based on non primary key

Question

Net core and EF Core DB first approach. I have one table and It has Id which is primary key and one more countryname which is non primary key. I want to query country name and I will not be passing primary key. Below is my implementation.

IBaseRepository.cs

public interface IBaseRepository<T>
 {
  async Task<T> GetCountryByNameAsync(string country)
 }

BaseRepository.cs

public class BaseRepository<T>: IBaseRepository<T>
        where T : class
    {
      private readonly DbContext dbContext;
      private readonly DbSet<T> dbSet;
      public BaseRepository(DbContext dbContext)
        {
            this.dbContext = dbContext;
            this.dbSet = dbContext?.Set<T>();
        }
       public async Task<T> GetCountryByNameAsync(string country)
        {
            return await this.dbSet.FindAsync(id).ConfigureAwait(false); //This will return based on the countryId
            //I want select * from country where countryname = country
        }
    }

In the above implementation I can get country by id(primary key) but I want to query based on the countryname. I am trying to figure it out. Can someone guide me how we can accomplish this. Any help would be greatly appreciated. Thanks

Mohamad Mousheimish · Accepted Answer · 2020-06-09T12:00:09.043

2

If you want to get the first element with the provided country name use the FirstOrDefault method. Then Check if the returned value is null (Will return null in case countryName does not exist).

public async Task<T> GetCountryByNameAsync(string country)
{
    var country = await this.dbSet<T>.FirstOrDefault(c=>c.Countryname == country); 
    return country;
}

edited Jun 09 '20 at 12:00

answered Jun 09 '20 at 11:51

Mohamad Mousheimish

1,641
3
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Thanks for your answer. I am not able to get C.countryname and it shows options equals, gethashcode, gettype and tostring – Niranjan godbole Jun 09 '20 at 11:53
Check the code now I forgot the generic type . One more thing, the generic type T. Should extend a class where the class contain an attribute called `countryName`. Did you got what I mean? – Mohamad Mousheimish Jun 09 '20 at 12:01
1

Because now, nothing says that the generic type `T` we're using contains an attribute called `countryName` – Mohamad Mousheimish Jun 09 '20 at 12:02

keuleJ · Answer 2 · 2020-06-09T12:07:17.943

1

Just use FirstOrDefaultAsync

    public async Task<T> GetCountryByNameAsync(string country)
    {
        return await this.dbSet<Country>.FirstOrDefaultAsync(c=>c.Countryname == country).ConfigureAwait(false); 
    }

edited Jun 09 '20 at 12:07

answered Jun 09 '20 at 11:48

keuleJ

3,418
4
30
51

Thanks for your answer. I am not able to get C.countryname and it shows options equals, gethashcode, gettype and tostring – Niranjan godbole Jun 09 '20 at 11:53
Ah normally you should have a DbSet or something like that on your DbContext... I suspect you have to make a CountryRepository : BaseRepository – keuleJ Jun 09 '20 at 12:09

Ef core query based on non primary key

2 Answers2