ProjectionExpressions in DynamoDB

AWS Dynamo DB
1

I am having issues using the ProjectionExoression field in the DynamoDb Database. I am calling this unfinished code like the following and still get all properties.

var query = Db.FromScan<Domain.Organization>();
                    //var projections = PrintPropertyNames<Domain.Organization>(",", c => c.Name, c => c.Metadata.LastUpdated, c => c.Metadata.Created);
                    query.ProjectionExpression = PrintPropertyNames<Domain.Organization>(c => c.Name).Join(", ");

                    //TODO: Only get the Required Fields

                    var data = query.Select<Domain.Organization>(x => x.Name).Exec();
                    if (message.Sort != null)
                    {
                        var sort = message.Sort[0];
                        var sortOrder = sort.Dir.EqualsIgnoreCase("asc") ? "ASC" : "DESC";
                        if (sort.Field.EqualsIgnoreCase("Name"))
                            data = sortOrder.EqualsIgnoreCase("ASC")
                                ? data.OrderBy(x => x.Name)
                                : data.OrderByDescending(x => x.Name);
                        else if (sort.Field.EqualsIgnoreCase("metadata.lastUpdated"))
                        {
                            data = sortOrder.EqualsIgnoreCase("ASC")
                                ? data.OrderBy(x => x.Metadata.LastUpdated)
                                : data.OrderByDescending(x => x.Metadata.LastUpdated);
                        }
                    }

                    var result = message.ConvertTo<ListOrganizationsCommandResult>();
                    result.Data = new List<object>(data);
                    return result;
2

Please be more specific with the exact Issue and/or Exception thrown (with full StackTrace).
Please also provide a reproducible example which we can run locally to repro the issue.

3

The issue is that event though I am specifying on the Name in the ProjectionExpression, it is returning all Properties and is not providing any error/exception. The above is the code I am using. But here is the full code file:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Threading.Tasks;
using MediatR;
using Microsoft.AspNetCore.Http;
using ServiceStack;
using ServiceStack.Aws.DynamoDb;
using SimOpSolutions.Infrastructure;
using SimOpSolutions.Tasks.Command.CommandResult.Organization;
using SimOpSolutions.Tasks.Command.Commands.Organization;
using SimOpSolutions.Tasks.Exceptions;

namespace SimOpSolutions.Tasks.Command.CommandHandlers.Organization
{


    public class ListOrganizationsCommandHandler :
        IAsyncRequestHandler<ListOrganizationsCommand, ListOrganizationsCommandResult>
    {
        public ListOrganizationsCommandHandler(IPocoDynamo db, IHttpContextAccessor accessor)
        {
            Db = db;
            User = new TokenUser(accessor.HttpContext.User);
        }

        public IPocoDynamo Db { get; set; }
        public TokenUser User { get; set; }

        public static List<string> PrintPropertyNames<T>(params Expression<Func<T, object>>[] properties)
        {
            var returnValues = new List<string>();
            foreach (var p in properties)
            {
                try
                {
                    var name = string.Empty;
                    if (p.Body is MemberExpression)
                    {
                        name = ((MemberExpression)p.Body).Member.Name;
                    }
                    else
                    {
                        var op = ((UnaryExpression)p.Body).Operand;
                        name = ((MemberExpression)op).Member.Name;
                    }
                    returnValues.Add(name);
                }
                catch (Exception ex)
                {
                    
                }
            }
            return returnValues;
        }

        public async Task<ListOrganizationsCommandResult> Handle(ListOrganizationsCommand message)
        {
            if (User.IsUserInRole(TokenUser.ApplicationRole.GlobalAdministrators))
            {
                /*message.Take = message.Take == 0 ? 20 : message.Take;
                var data = Db.FromScan<Domain.Organization>().Exec(message.Take);
                var result = message.ConvertTo<ListOrganizationsCommandResult>();
                result.Data = new List<object>(data);
                return result;*/

                try
                {
                    message.Take = message.Take == 0 ? 20 : message.Take;
                    var query = Db.FromScan<Domain.Organization>();
                    //var projections = PrintPropertyNames<Domain.Organization>(",", c => c.Name, c => c.Metadata.LastUpdated, c => c.Metadata.Created);
                    //query.ProjectionExpression = PrintPropertyNames<Domain.Organization>(c => c.Name).Join(", ");

                    //TODO: Only get the Required Fields

                    var data = query.Select<Domain.Organization>().Exec();
                    if (message.Sort != null)
                    {
                        var sort = message.Sort[0];
                        var sortOrder = sort.Dir.EqualsIgnoreCase("asc") ? "ASC" : "DESC";
                        if (sort.Field.EqualsIgnoreCase("Name"))
                            data = sortOrder.EqualsIgnoreCase("ASC")
                                ? data.OrderBy(x => x.Name)
                                : data.OrderByDescending(x => x.Name);
                        else if (sort.Field.EqualsIgnoreCase("metadata.lastUpdated"))
                        {
                            data = sortOrder.EqualsIgnoreCase("ASC")
                                ? data.OrderBy(x => x.Metadata.LastUpdated)
                                : data.OrderByDescending(x => x.Metadata.LastUpdated);
                        }
                    }

                    var result = message.ConvertTo<ListOrganizationsCommandResult>();
                    result.Data = new List<object>(data);
                    return result;
                }
                catch(Exception ex)
                {
                    return new ListOrganizationsCommandResult();
                }
            }
            throw new NotAuthorizedException();
        }
    }
}
4

Use an anonymous type to specify the the fields you want returned, e.g:

var data = query.Select<Domain.Organization>(x => new { x.Name }).Exec();
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