如何在Xamarin中添加DatePicker的最小日期验证检查

Question

我有两个DatePicker(命名为fromdate和todate)和一个按钮(命名为save).

默认情况下,今天的日期将填入DatePicker.我已经添加了最小日期验证(用户只能选择今天或更长的日期.

如果今天的日期是5月30日,并且用户选择6月15日fromdate并点击确定.现在显示默认的今天日期todate.我想要验证,如果用户选择6月15日fromdate并点击确定,那么todate应该填充fromdate.

Answer 1

这可以通过将toDate DatePicker的MinimumDate绑定到FromDate属性来完成.

我不知道你的代码所以我会给你一个例子:

想象一下,你有一个像这样的XAML:

<?xml version="1.0" encoding="utf-8"?>
<ContentPage 
    xmlns="http://xamarin.com/schemas/2014/forms" 
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" 
    xmlns:local="clr-YourProject" 
    x:Class="YourProject.YourClass">

    <StackLayout>
        <DatePicker Date="{Binding FromDate}" MinimumDate="{Binding FromMiminumDate}" />

        <DatePicker Date="{Binding ToDate}" MinimumDate="{Binding FromDate}" />
    </StackLayout>
</ContentPage>

你有一个像这样的ViewModel:

public class YourViewModel : INotifyPropertyChanged
{
    public YourViewModel ()
    {
        FromMiminumDate = DateTime.Today;
    }

    private DateTime _fromDate;
    public DateTime FromDate
    {
        get { return _fromDate; }
        set
        {
            if (_fromDate == value)
                return;

            _fromDate = value;
            NotifyPropertyChanged (nameof(FromDate));
        }
    }

    private DateTime _toDate;
    public DateTime ToDate
    {
        get { return _toDate; }
        set
        {
            if (_toDate == value)
                return;

            _toDate = value;
            NotifyPropertyChanged (nameof(ToDate));
        }
    }

    private DateTime _fromMiminumDate;
    public DateTime FromMiminumDate
    {
        get { return _fromMiminumDate; }
        set
        {
            if (_fromMiminumDate == value)
                return;

            _fromMiminumDate = value;
            NotifyPropertyChanged (nameof(FromMiminumDate));
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    void NotifyPropertyChanged (string propertyName)
    {
        PropertyChanged?.Invoke (this, new PropertyChangedEventArgs (propertyName));
    }
}

这将使每次更改FromDate Picker中选择的日期时,ToDate Picker的MinimumDate也将更改.

当然,后面的XAML代码将如下所示:

public YourClass ()
{
    var VM = new YourViewModel ();

    InitializeComponent ();

    BindingContext = VM;
}

希望这可以帮助.