Sample file for blog post. https://abcserverless.pl/aws-parameter-store-i-net-core/

AWSParameterStore.cs

using Amazon.SimpleSystemsManagement;
using Amazon.SimpleSystemsManagement.Model;
using System.Threading.Tasks;

namespace AWSParameterStore
{
    public class ParameterAWSStore
    {
        private static readonly string databaseString = "DATABASE_HOST";
        private static readonly string databaseName = "DATABASE_NAME";
        private static readonly string databaseUser = "DATABASE_USER";
        private static readonly string databasePassword = "DATABASE_PASSWORD";

        public static async Task<string> GetDatabaseHost(bool encrypted)
        {
            return await getParameter(databaseString, encrypted);
        }

        public static async Task<string> GetDatabaseName(bool encrypted)
        {
            return await getParameter(databaseName, encrypted);
        }

        public static async Task<string> GetDatabaseUser(bool encrypted)
        {
            return await getParameter(databaseUser, encrypted);
        }

        public static async Task<string> GetDatabasePassword(bool encrypted)
        {
            return await getParameter(databasePassword, encrypted);
        }

        public static async Task<bool> SetParameter(string parameterName, string parameterValue, bool withEncryption)
        {
            var client = getClient();
            var request = putRequest(parameterName, parameterValue, withEncryption);
            if (withEncryption)
            {
                request.Type = ParameterType.SecureString;
            }
            else
            {
                request.Type = ParameterType.String;
            }
            var response = await client.PutParameterAsync(request);
            return response.HttpStatusCode == System.Net.HttpStatusCode.OK;
        }

        private static GetParameterRequest getRequest(string parameterName, bool withDecryption)
        {
            var request = new GetParameterRequest();
            request.Name = parameterName;
            request.WithDecryption = withDecryption;
            return request;
        }

        private static PutParameterRequest putRequest(string parameterName, string parameterValue, bool withDecryption)
        {
            var request = new PutParameterRequest();
            request.Name = parameterName;
            request.Value = parameterValue;
            request.Overwrite = true;
            request.Type = withDecryption ? ParameterType.SecureString : ParameterType.String;
            return request;
        }

        private static async Task<string> getParameter(string parameterName, bool encrypted)
        {
            var client = getClient();
            var result = await client.GetParameterAsync(getRequest(parameterName, encrypted));
            return result.Parameter.Value.ToString();
        }

        private static AmazonSimpleSystemsManagementClient getClient()
        {
            var client = new AmazonSimpleSystemsManagementClient(".accessKeyId.", ".secretAccessKey.", Amazon.RegionEndpoint.EUCentral1);
            return client;
        }
    }
}