Update a list in c#

Question

I have repository class which contains a list with people who filled in a form on my website if they will attend on my party or not. I read values with the GetAllRespones and I add values to the list with AddResponse (via an interface)

Now I want to check if someone already filled in my form and if so I want to check if the value of WillAttend is changed and update it.

I can see what I did below here

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using PartyInvites.Abstract;

namespace PartyInvites.Models
{
public class GuestResponseRepository : IRepository

{
    private static List<GuestResponse> responses = new List<GuestResponse>();

    IEnumerable<GuestResponse> IRepository.GetAllResponses()
    {
        return responses;
    }

    bool IRepository.AddResponse(GuestResponse response)
    {
       bool exists = responses.Any(x => x.Email == response.Email);
        bool existsWillAttend = responses.Any(x => x.WillAttend == response.WillAttend);

        if (exists == true)
        {
            if (existsWillAttend == true)
            {
                return false;
            }

           var attend =  responses.Any(x => x.Email == response.Email && x.WillAttend == response.WillAttend);
           attend.WillAttend = response.WillAttend;
           return true;

        }

        responses.Add(response);
        return true;
    }
}
}

the problem is, i get a error message at "attend.WillAttend"

the error is: bool does not contain definition for WillAttend and has no extension method 'WillAttend' accepting a first argument of type bool could be found

Could anyone help me out fix my code? :)

Roman · Accepted Answer · 2017-02-24 16:21:08Z

7

The problem is here:

var attend = 
        responses.Any(x => x.Email == response.Email && x.WillAttend == response.WillAttend);

Any<>() returns bool. bool doen't have property WillAttend. If you want to get first response with x => x.Email == response.Email && x.WillAttend == response.WillAttend use First() (or FirstOrDefault() but in your case you always will have at least one element, so simply use First()):

var attend = responses.First(x => x.Email == response.Email && x.WillAttend != response.WillAttend);
attend.WillAttend = response.WillAttend;

If you want many responses with specified condition use Where():

var attend = responses.Where(x => x.Email == response.Email && x.WillAttend != response.WillAttend);

if (attend.Any())
{
    //do something
}

Also, you can make your method simpler:

bool IRepository.AddResponse(GuestResponse response)
{
    if (responses.Any(x => x.Email == response.Email)) //here
    {
        if (responses.Any(x => x.WillAttend != response.WillAttend)) //here
        {
            return false;
        }

        var attend = responses.First(x => x.Email == response.Email && x.WillAttend != response.WillAttend);
        attend.WillAttend = response.WillAttend;          
        return true;
    }

    responses.Add(response);
    return true;
}

edited Feb 24, 2017 at 16:21

answered Feb 24, 2017 at 14:36

Roman

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3 Comments

valheru Over a year ago

Thank you for the fast reply! Implemented the code you suggested, but for some reason var attend keeps being null. Any ideas about that?

Roman Over a year ago

@valheru, have you got NullReferenceException or seen value using debugger?

valheru Over a year ago

Fixed it with x.WillAttend != response.WillAttend as suggested by Tamás Szabó and it works fine now. Thank you very much with your help!

Tamás Szabó · Accepted Answer · 2017-02-24 14:37:15Z

2

responses.Any(...) returns a bool value (whether responses contains a value you specified). You will have to actually get that value with

responses.First(<lambda expression you specified>)

for example and get WillAttend on that object.

answered Feb 24, 2017 at 14:37

Tamás Szabó

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5 Comments

valheru Over a year ago

Thanks that did the trick! To bad an other problem occurred after it

Tamás Szabó Over a year ago

What was it? Maybe I can help.

valheru Over a year ago

var attend keeps being 'null'

Tamás Szabó Over a year ago

That must be because there is no object that meets the criteria you specified with the lambda expression. I think you should write x.WillAttend != response.WillAttend since you are looking for a change in attendance.

valheru Over a year ago

Thanks a lot that was the problem! So stupid I didn't think about it myself :)

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