ADO.NET implementation example of a repository.

CategoryRepositoryADO.cs

public class CategoryRepositoryADO : ICategoryRepository
{
  public async Task<IEnumerable<Category>> ListAsync()
  {
      var categories = new List<Category>();

      using(var connection = new SqlConnection("connection_string"))
      using(var command = new SqlCommand())
      {
          command.Connection = connection;
          command.CommandType = CommandType.StoredProcedure;
          command.CommandText = "StoredProcedureName";

          connection.Open();
          using(var reader = await command.ExecuteReaderAsync())
          {
              while(await reader.ReadAsync())
              {
                  var category = new Category
                  {
                      Id = Convert.ToInt32(reader["Id"]),
                      // Fill other fields
                  };
              }
          }
          connection.Close();
      }

      return categories;
  }
  
  // Other methods
}