如何从 api 响应 Xamarin Forms 多次修改 ObservableCollection 中的数据

如何解决如何从 api 响应 Xamarin Forms 多次修改 ObservableCollection 中的数据

我正在用响应和报告 api 填充 ObservableCollection，其中包含来自 Json 格式数组的以下数据：

[
 {
   "date": "2021-06-08 11:46:55","product": "EXCHANGE","amount": 1,"total": "90","points": "90","id": "5581"
 },{
  "date": "2021-06-03 17:33:00","product": "GNV","amount": "80","total": "270","points": "27","id": 102959
 },]

“还有更多类似的数据，但我将这两个示例放在一起，因为我以这种格式接收它们”

所以我将数据添加到 ObservableCollection

   public class WebApiClientService
    {
        private HttpClient _client;

        public WebApiClientService()
        {
            _client = new HttpClient();
        }
        public async Task<T> CallPostTransactionsTask<T>(object objectParams)
        {
            Uri uri = new Uri(string.Format(Constants.urlTransactions));

            try
            {
                var jsonData = JsonConvert.SerializeObject(objectParams);
                var contentJson = new StringContent(jsonData,Encoding.UTF8,"application/json");
                HttpResponseMessage response = await _client.PostAsync(uri,contentJson);

                if (response.IsSuccessStatusCode)
                {
                    var jsonResult = await response.Content.ReadAsStringAsync();
                    return JsonConvert.DeserializeObject<T>(jsonResult);
                }
                else
                {
                    return default(T);
                }
            }
            catch (Exception e)
            {
                Console.WriteLine(e);
                throw;
            }
        }
    }

public class TransaccionesResponseModel
    {
        public DateTime date{ get; set; }
        public string product{ get; set; }
        public double amount{ get; set; }
        public int total { get; set; }
        public double points{ get; set; }
        public int id { get; set; }
    }

public class TransactionsPageViewModel : BaseViewModel
{
    private WebApiClientService webApi = new WebApiClientService();

    private ObservableCollection<TransaccionesResponseModel> listTransactions;

    public ObservableCollection<TransaccionesResponseModel> ListTransactions
    {
        get
        {
            return this.listTransactions;
        }

        set
        {
            if (this.listTransactions == value)
            {
                return;
            }

            this.SetProperty(ref this.listTransactions,value);
        }
    }
    public TransactionsPageViewModel()
    {
        CheckTransactions();
    }
    public async void CheckTransactions()
    {
        var transactionConsult = new
        {
          codeClient = "909090",dateStart= "2021-02-01 00:00:00",dateEnd= "2021-06-10 23:59:59"
        };
        ListTransactions= await webApi.CallPostTransactionsTask<ObservableCollection<TransaccionesResponseModel>>(transactionConsult);
    }
}

在 XAML 中

<ContentPage.Content>
    <StackLayout Padding="5">
        <CollectionView ItemsSource="{Binding ListTransactions}">
            <CollectionView.ItemTemplate>
                <DataTemplate>
                    <Grid Padding="10,0" RowDefinitions="Auto,Auto">
                        <Frame
                            Padding="5"
                            BackgroundColor="White"
                            BorderColor="#C5740C"
                            CornerRadius="5"
                            IsClippedToBounds="False">
                            <Grid ColumnDefinitions="*,*">

                                <StackLayout Grid.Column="0">
                                    <Label Text="Date:" />
                                    <Label Text="Product:"/>
                                    <Label Text="Amount:"/>
                                    <Label Text="Points:" />
                                    <Label Text="Id:" />
                                </StackLayout>

                                <StackLayout Grid.Column="1">
                                    <Label
                                        BackgroundColor="Transparent"
                                        HorizontalTextAlignment="End"
                                        Text="{Binding date,StringFormat='{0:dd/MM/yyyy HH:mm}'}" />
                                    <Label
                                        BackgroundColor="Transparent"
                                        HorizontalTextAlignment="End"
                                        Text="{Binding product}" />
                                    <Label
                                        BackgroundColor="Transparent"
                                        HorizontalTextAlignment="End"
                                        Text="{Binding amount,StringFormat='{0:#,0.#0}'}" />
                                    <Label
                                        BackgroundColor="Transparent"
                                        HorizontalTextAlignment="End"
                                        Text="{Binding total,StringFormat='{0:#.00}'}" />
                                    <Label
                                        BackgroundColor="Transparent"
                                        HorizontalTextAlignment="End"
                                        Text="{Binding points,0.#0}'}" />
                                    <Label
                                        BackgroundColor="Transparent"
                                        HorizontalTextAlignment="End"
                                        Text="{Binding id}" />
                                </StackLayout>
                            </Grid>
                        </Frame>
                    </Grid>
                </DataTemplate>
            </CollectionView.ItemTemplate>
        </CollectionView>
    </StackLayout>
</ContentPage.Content>

它把我画成这样：

date:          2021-06-08 11:46
product:               EXCHANGE
amount:                       1
total:                       90
points:                      90
id:                        5581

date:          2021-06-03 17:33
product:                    GNV
amount:                      80
total:                      270
points:                      27
id:                      102959

现在我想增加 - 的符号

到 points: 90 时：product: EXCHANGE

当每个 product 等于 EXCHANGE 时，我想以这种方式得到结果：

date:          2021-06-08 11:46
product:               EXCHANGE
amount:                       1
total:                       90
points:                     -90
id:                        5581

解决方法

使用 LINQ 获取匹配的交易

var match = myCollection.Where(x => x.product == "EXCHANGE").ToList();

然后更新匹配的项目

foreach (var m in match)
{
  m.points = -90;
  // modify any other properties here
}