概念

數(shù)據(jù)綁定連接兩個(gè)對(duì)象臂外，稱為源和目標(biāo)伴澄。源對(duì)象提供數(shù)據(jù)。目標(biāo)對(duì)象將消耗（并經(jīng)常顯示）來(lái)自源對(duì)象的數(shù)據(jù)账劲。例如戳护，Label（目標(biāo)對(duì)象）通常將其Text屬性綁定到源對(duì)象中的公共字符串屬性。下圖說(shuō)明了綁定關(guān)系：

1

建立數(shù)據(jù)綁定是一個(gè)兩步過(guò)程

目標(biāo)對(duì)象的BindingContext屬性必須設(shè)置為源
目標(biāo)和來(lái)源之間必須建立約束。在XAML中榛瓮，這是通過(guò)使用綁定標(biāo)記擴(kuò)展來(lái)實(shí)現(xiàn)的铺董。在C＃中，這是通過(guò)SetBinding方法實(shí)現(xiàn)的
有關(guān)數(shù)據(jù)綁定的更多信息榆芦，請(qǐng)參閱https://developer.xamarin.com/guides/xamarin-forms/xaml/xaml-basics/data_binding_basics/

綁定方式

1.XAML
2.C#

XAML

前端Binding

<StackLayout Padding="0,20,0,0">
    <Label Text="Forename:" />
    <Entry Text="{Binding Forename, Mode=TwoWay}" />
    <Label Text="Surname:" />
    <Entry Text="{Binding Surname, Mode=TwoWay}" />
    <StackLayout Padding="0,20,0,0" Orientation="Horizontal">
        <Label Text="Your forename is:" />
        <Label Text="{Binding Forename}" />
    </StackLayout>
    <StackLayout Orientation="Horizontal">
        <Label Text="Your surname is:" />
        <Label Text="{Binding Surname}" />
    </StackLayout>
</StackLayout>

后臺(tái)BindingContext賦值

BindingContext = new DetailsViewModel();

DetailsViewModel類

public class DetailsViewModel : INotifyPropertyChanged
{
    string forename, surname;

    public string Forename
    {
        get
        {
            return forename;
        }
        set
        {
            if (forename != value)
            {
                forename = value;
                OnPropertyChanged("Forename");
            }
        }
    }

    public string Surname
    {
        get
        {
            return surname;
        }
        set
        {
            if (surname != value)
            {
                surname = value;
                OnPropertyChanged("Surname");
            }
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged(string propertyName)
    {
        var changed = PropertyChanged;
        if (changed != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

示例代碼

https://github.com/zLulus/NotePractice/tree/dev3/Xamarin.Forms/XamarinDemo/XamarinDemo/XamarinDemo/Bindings 的BindingFirstName2

使用內(nèi)置模板TextCell進(jìn)行數(shù)據(jù)綁定(C#)

進(jìn)行數(shù)據(jù)綁定

//Model
Employee employeeToDisplay = new Employee();

//輸入框
var firstNameEntry = new Entry()
{
    HorizontalOptions = LayoutOptions.FillAndExpand
};
//綁定  下面兩個(gè)綁定柄粹，任選其一即可   
this.BindingContext = employeeToDisplay;
firstNameEntry.SetBinding(Entry.TextProperty, "FirstName");

Employee類
實(shí)現(xiàn)接口INotifyPropertyChanged喘鸟，F(xiàn)irstName在set時(shí)，觸發(fā)OnPropertyChanged方法

public class Employee : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    string _firstName;
    public string FirstName
    {
        get { return _firstName; }
        set
        {
            if (value.Equals(_firstName, StringComparison.Ordinal))
            {
                // Nothing to do - the value hasn't changed;
                return;
            }
            _firstName = value;
            OnPropertyChanged();

        }
    }

    void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        var handler = PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

查看綁定結(jié)果

//查詢按鈕
Button getValueButton = new Button();
getValueButton.Text = "查看結(jié)果";
getValueButton.Clicked += (async (sender, e) =>
{
    await DisplayAlert("綁定結(jié)果",$"當(dāng)前Entry的Text是{firstNameEntry.Text},后臺(tái)實(shí)體的FirstName是{employeeToDisplay.FirstName}","確定");
});

示例代碼

https://github.com/zLulus/NotePractice/tree/dev3/Xamarin.Forms/XamarinDemo/XamarinDemo/XamarinDemo/Bindings 的BindingFirstName