PostGreSQLReadThruProvider.cs

using Alachisoft.NCache.Runtime.Caching;
using Alachisoft.NCache.Runtime.DatasourceProviders;
using Alachisoft.NCache.Samples.PostGreSQLNotificationDependency;
using Npgsql;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Data;
using Entities;

namespace PostGreSQLBackingSourceProvider
{
    public class PostGreSQLReadThruProvider : IReadThruProvider
    {
        private string _connectionString;
        private string _dependencyKey;
        private string _schema;
        private string _table;
        private string _channel;


        private IDbConnection _connection;
        public void Init(IDictionary parameters, string cacheId)
        {
            _connectionString = parameters["connectionString"] as string;
            _connection = new NpgsqlConnection(_connectionString);
            _connection.Open();
        }

        public ProviderDataTypeItem<IEnumerable> LoadDataTypeFromSource(string key, DistributedDataType dataType)
        {
            throw new NotImplementedException();
        }

        public ProviderCacheItem LoadFromSource(string key)
        {
            var query = $"SELECT customerid, address, country, city FROM customers WHERE customerid = '{key}'";
            // Define a query returning a single row result set
            NpgsqlCommand command = new NpgsqlCommand(query, _connection as NpgsqlConnection);
            var reader = command.ExecuteReader();
            ProviderCacheItem providerCacheItem = null;
            while (reader.Read())
            {
                if (providerCacheItem == null)
                {
                    var customer = new Customer()
                    {
                        customerid = reader[0] as string,
                        address = reader[1] as string,
                        country = reader[2] as string,
                        city = reader[3] as string,
                    };
                    providerCacheItem = new ProviderCacheItem(customer)
                    {
                        Dependency = new PostGreSQLDependency(_connectionString, customer.customerid, "public", "customers", "customer_channel"),
                        ResyncOptions = new ResyncOptions(true)
                    };
                }
            }
            reader.Close();

            return providerCacheItem;
        }

        public IDictionary<string, ProviderCacheItem> LoadFromSource(ICollection<string> keys)
        {
            throw new NotImplementedException();
        }

        public void Dispose()
        {
            _connection.Close();
        }
    }
}