DevExpress WPF v21.2正式版下載

類實現(xiàn) INotifyPropertyChanged 接口，并提供 API 以最少的編碼聲明可綁定屬性。

可綁定屬性

要聲明可綁定屬性，請執(zhí)行以下操作：

• 從 BindableBase 類繼承您的 ViewModel；
• 在屬性 getter 和 setter 中使用 GetValue 和 SetValue 方法。

C#

using DevExpress.Mvvm;

public class ViewModel : BindableBase {
public string FirstName {
get { return GetValue<string>(nameof(FirstName)); }
set { SetValue(value, nameof(FirstName)); }
}
}

VB.NET

Imports DevExpress.Mvvm

Public Class ViewModel
Inherits BindableBase
Public Property FirstName() As String
Get
Return GetValue(Of String)(NameOf(FirstName))
End Get
Set(ByVal value As String)
SetValue(value, NameOf(FirstName))
End Set
End Property
End Class

BindableBase 類公開使用 CallerMemberNameAttribute 的 GetValue 和 SetValue 重載，您不必將屬性名稱傳遞給這些方法的參數(shù)，這簡化了可綁定屬性聲明：

C#

using DevExpress.Mvvm;

public class ViewModel : BindableBase {
public string FirstName {
get { return GetValue<string>(); }
set { SetValue(value); }
}
}

VB.NET

Imports DevExpress.Mvvm

Public Class ViewModel
Inherits BindableBase
Public Property FirstName() As String
Get
Return GetValue(Of String)()
End Get
Set(ByVal value As String)
SetValue(value)
End Set
End Property
End Class

注意：在 .NET Framework 4.5 及更高版本中可用。

屬性值存儲在內(nèi)部字典中：

• GetValue 方法使用此字典獲取屬性值；
• SetValue 方法使用屬性名稱作為鍵將屬性值存儲在字典中。

SetValue 方法返回指示屬性是否已更改的 True 或 False 值。 如果為屬性設(shè)置相同的值，SetValue 方法將返回 False，并且不會發(fā)送更改通知。

C#

using DevExpress.Mvvm;

public class ViewModel : BindableBase {
public string FirstName {
get { return GetValue<string>(); }
set {
if (SetValue(value))
NotifyFullNameChanged();
else MessageBox.Show("Could not change value!");
}
}
}

VB.NET

Imports DevExpress.Mvvm

Public Class ViewModel
Inherits BindableBase
Public Property FirstName() As String
Get
Return GetValue(Of String)()
End Get
Set(ByVal value As String)
If Not SetValue(value) Then
NotifyFullNameChanged()
Else MessageBox.Show("Could not change value!")
End If
End Set
End Property
End Class

屬性值更改時運行自定義代碼

SetValue 方法具有將回調(diào)方法作為參數(shù)的重載，在更改屬性值后調(diào)用此回調(diào)。

C#

using DevExpress.Mvvm;

public class ViewModel : BindableBase {
public string FirstName {
get { return GetValue<string>(); }
set { SetValue(value, changedCallback: OnFirstNameChanged); }
}
void OnFirstNameChanged() {
//...
}
}

VB.NET

Imports DevExpress.Mvvm

Public Class ViewModel
Inherits BindableBase
Public Property FirstName() As String
Get
Return GetValue(Of String)()
End Get
Set(ByVal value As String)
SetValue(value, changedCallback:= AddressOf OnFirstNameChanged)
End Set
End Property
Sub OnFirstNameChanged()
'...
End Sub
End Class

手動引發(fā) INotifyPropertyChanged.PropertyChanged

如果您需要為特定屬性引發(fā) INotifyPropertyChanged.PropertyChanged 事件，請使用 RaisePropertyChanged/RaisePropertiesChanged 方法。

C#

using DevExpress.Mvvm;

public class ViewModel : BindableBase {
public string FirstName {
get { return GetValue<string>(); }
set { SetValue(value, changedCallback: NotifyFullNameChanged); }
}

public string LastName {
get { return GetValue<string>(); }
set { SetValue(value, changedCallback: NotifyFullNameChanged); }
}

public string FullName { get { return FirstName + " " + LastName; } }

void NotifyFullNameChanged() {
RaisePropertyChanged(nameof(FullName));
}
}

VB.NET

Imports DevExpress.Mvvm

Public Class ViewModel
Inherits BindableBase
Public Property FirstName() As String
Get
Return GetValue(Of String)()
End Get
Set(ByVal value As String)
SetValue(value, changedCallback:= AddressOf NotifyFullNameChanged)
End Set
End Property

Public Property LastName() As String
Get
Return GetValue(Of String)()
End Get
Set(ByVal value As String)
SetValue(value, changedCallback:= AddressOf NotifyFullNameChanged)
End Set
End Property

Public ReadOnly Property FullName() As String
Get
Return FirstName & " " & LastName
End Get
End Property

Private Sub NotifyFullNameChanged()
RaisePropertyChanged(Function() FullName)
End Sub
End Class

使用帶有支持字段的屬性

當(dāng)一個屬性被頻繁訪問或更新時，應(yīng)用程序的性能可能會降低，因為屬性值存儲在字典中。 要提高應(yīng)用程序的性能，請將屬性值存儲在支持字段中。

C#

using DevExpress.Mvvm;

public class ViewModel : BindableBase {
string _FirstName;
public string FirstName {
get { return _FirstName; }
set { SetValue(ref _FirstName, value, changedCallback: NotifyFullNameChanged); }
}
}

VB.NET

Imports DevExpress.Mvvm

Public Class ViewModel
Inherits BindableBase
Private _FirstName As String
Public Property FirstName() As String
Get
Return _FirstName
End Get
Set(ByVal value As String)
SetValue(_FirstName, value, changedCallback:= AddressOf NotifyFullNameChanged)
End Set
End Property
End Class

.NET Framework 4.0 中的 BindableBase

可綁定屬性

使用 GetProperty 和 SetProperty 方法來實現(xiàn)可綁定屬性。

C#

using DevExpress.Mvvm;

public class ViewModel : BindableBase {
public string FirstName {
get { return GetProperty(() => FirstName); }
set { SetProperty(() => FirstName, value); }
}
}

VB.NET

Imports DevExpress.Mvvm

Public Class ViewModel
Inherits BindableBase
Public Property FirstName As String
Get
Return GetProperty(Function() FirstName)
End Get
Set(value As String)
SetProperty(Function() FirstName, value)
End Set
End Property
End Class

GetProperty 和 SetProperty 方法的第一個參數(shù)是一個 lambda 表達(dá)式，它返回用于標(biāo)識目標(biāo)屬性名稱的屬性。 屬性名稱是使用靜態(tài) BindableBase.GetPropertyName<T> 方法在內(nèi)部獲取的。

屬性值更改時運行自定義代碼

SetProperty 方法返回指示屬性是否已更改的 True 或 False 值。如果將該屬性設(shè)置為相同的值，SetProperty 方法將返回 False，并且不會發(fā)送更改通知。 SetProperty 方法具有將回調(diào)方法作為參數(shù)的重載，此回調(diào)在字段更改后調(diào)用。

C#

using DevExpress.Mvvm;

public class ViewModel : BindableBase {
public string FirstName {
get { return GetProperty(() => FirstName); }
set { SetProperty(() => FirstName, value, OnFirstNameChanged); }
}
void OnFirstNameChanged() {
//...
}
}

VB.NET

Imports DevExpress.Mvvm

Public Class ViewModel
Inherits BindableBase
Public Property FirstName As String
Get
Return GetProperty(Function() FirstName)
End Get
Set(value As String)
SetProperty(Function() FirstName, value, AddressOf OnFirstNameChanged)
End Set
End Property
Sub OnFirstNameChanged()
'...
End Sub
End Class

手動引發(fā) INotifyPropertyChanged.PropertyChanged

如果您需要為特定屬性引發(fā) INotifyPropertyChanged.PropertyChanged 事件，請使用 RaisePropertyChanged/RaisePropertiesChanged 方法。

C#

using DevExpress.Mvvm;

public class ViewModel : BindableBase {
public string FullName {
get { return string.Format("{0} {1}", FirstName, LastName); }
}
public string FirstName {
get { return GetProperty(() => FirstName); }
set { SetProperty(() => FirstName, value, OnFirstNameChanged); }
}
public string LastName {
get { return GetProperty(() => LastName); }
set {
if(SetProperty(() => LastName, value))
RaisePropertyChanged(() => FullName);
}
}
void OnFirstNameChanged() {
RaisePropertyChanged(() => FullName);
}
}

VB.NET

Imports DevExpress.Mvvm

Public Class ViewModel
Inherits BindableBase
Public ReadOnly Property FullName As String
Get
Return String.Format("{0} {1}", FirstName, LastName)
End Get
End Property
Public Property FirstName As String
Get
Return GetProperty(Function() FirstName)
End Get
Set(value As String)
SetProperty(Function() FirstName, value, AddressOf OnFirstNameChanged)
End Set
End Property
Public Property LastName As String
Get
Return GetProperty(Function() LastName)
End Get
Set(value As String)
If SetProperty(Function() LastName, value) Then
RaisePropertyChanged(Function() FullName)
End If
End Set
End Property
Sub OnFirstNameChanged()
RaisePropertyChanged(Function() FullName)
End Sub
End Class

使用帶有支持字段的屬性

當(dāng)屬性被頻繁更新時（由于從 lambda 表達(dá)式計算屬性名稱并將屬性值存儲在字典中），應(yīng)用程序性能可能會降低。 要適應(yīng)這些情況，請使用存儲變量來存儲屬性，并使用 BindableBase.GetPropertyName<T> 方法從靜態(tài)構(gòu)造函數(shù)計算一次屬性名稱。

C#

using DevExpress.Mvvm;

public class ViewModel : BindableBase {
static string Property1Name;
static ViewModel() {
Property1Name = BindableBase.GetPropertyName(() => new ViewModel().Property1);
}

string property1;
public string Property1 {
get { return property1; }
set { SetProperty(ref property1, value, Property1Name); }
}
}

VB.NET

Imports DevExpress.Mvvm

Public Class ViewModel
Inherits BindableBase
Shared Property1Name As String
Shared Sub New()
Property1Name = BindableBase.GetPropertyName(Function() New ViewModel().Property1)
End Sub

Dim _Property1 As String
Public Property Property1 As String
Get
Return _Property1
End Get
Set(value As String)
SetProperty(_Property1, value, Property1Name)
End Set
End Property
End Class

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