根據(jù)您綁定得屬性，存在以下三種可能得情況：
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屬性依賴屬性依賴是來自同一個(gè)ViewModel得兩個(gè)屬性之間得關(guān)系，當(dāng)一個(gè)屬性發(fā)生變化時(shí)，另一個(gè)屬性會(huì)更新其值。
在“MVVM 可靠些實(shí)踐”演示中，多個(gè)模塊演示了以下設(shè)置：
對于使用示例 UI 得每個(gè)演示模塊，將 View 元素綁定到 ViewModel 屬性得代碼都是相同得。
C#
mvvmContext.ViewModelType = typeof(MultViewModel);var fluentAPI = mvvmContext.OfType<MultViewModel>();fluentAPI.SetBinding(editor1, e => e.EditValue, x => x.Operand1);fluentAPI.SetBinding(editor2, e => e.EditValue, x => x.Operand2);fluentAPI.SetBinding(resultLabel, l => l.Text, x => x.ResultText);
VB.NET
mvvmContext.ViewModelType = GetType(MultViewModel)Dim fluentAPI = mvvmContext.OfType(Of MultViewModel)()fluentAPI.SetBinding(editor1, Sub(e) e.EditValue, Sub(x) x.Operand1)fluentAPI.SetBinding(editor2, Sub(e) e.EditValue, Sub(x) x.Operand2)fluentAPI.SetBinding(resultLabel, Sub(l) l.Text, Sub(x) x.ResultText)
然而，屬性依賴在每個(gè)模塊中得聲明都不同。
onPropertyChanged 方法
在POCO ViewModels中，您可以聲明OnXChanged方法，其中 X 是屬性名稱。 當(dāng)相關(guān)屬性得值發(fā)生變化時(shí)，框架會(huì)調(diào)用這些方法。
C#
public class MultViewModel {public virtual int Operand1 { get; set; }public virtual int Operand2 { get; set; }public virtual int Result { get; set; }public virtual string ResultText { get; set; }protected void OnOperand1Changed() {UpdateResult();}protected void OnOperand2Changed() {UpdateResult();}protected void onResultChanged() {UpdateResultText();}void UpdateResult() {Result = Operand1 * Operand2;}void UpdateResultText() {ResultText = string.Format("The result is: {0:n0}", Result);}}
VB.NET
Public Class MultViewModelPublic Overridable Property Operand1() As IntegerPublic Overridable Property Operand2() As IntegerPublic Overridable Property Result() As IntegerPublic Overridable Property ResultText() As StringProtected Sub OnOperand1Changed()UpdateResult()End SubProtected Sub OnOperand2Changed()UpdateResult()End SubProtected Sub onResultChanged()UpdateResultText()End SubPrivate Sub UpdateResult()Result = Operand1 * Operand2End SubPrivate Sub UpdateResultText()ResultText = String.Format("The result is: {0:n0}", Result)End SubEnd Class
自定義更新方法
如果您得更新方法未被稱為“On...Changed”，請使用 DevExpress.Mvvm.DataAnnotations.BindableProperty 屬性告訴框架它應(yīng)該在屬性值更改時(shí)調(diào)用此方法。 在下面得代碼示例中，DevExpress.Mvvm.POCO.RaisePropertyChanged 是一個(gè) DevExpress 擴(kuò)展方法，它將更新通知發(fā)送到依賴屬性。
C#
public class SumViewModel {[BindableProperty(onPropertyChangedMethodName = "NotifyResultAndResultTextChanged")]public virtual int Operand1 { get; set; }[BindableProperty(onPropertyChangedMethodName = "NotifyResultAndResultTextChanged")]public virtual int Operand2 { get; set; }public int Result {get { return Operand1 + Operand2; }}public string ResultText {get { return string.Format("The result is: {0:n0}", Result); }}protected void NotifyResultAndResultTextChanged() {this.RaisePropertyChanged(x => x.Result);this.RaisePropertyChanged(x => x.ResultText);}}
VB.NET
Public Class SumViewModel<BindableProperty(onPropertyChangedMethodName := "NotifyResultAndResultTextChanged")>Public Overridable Property Operand1() As Integer<BindableProperty(onPropertyChangedMethodName := "NotifyResultAndResultTextChanged")>Public Overridable Property Operand2() As IntegerPublic Readonly Property Result() As IntegerGetReturn Operand1 + Operand2End GetEnd PropertyPublic Readonly Property ResultText() As StringGetReturn String.Format("The result is: {0:n0}", Result)End GetEnd PropertyProtected Sub NotifyResultAndResultTextChanged()Me.RaisePropertyChanged(Function(x) x.Result)Me.RaisePropertyChanged(Function(x) x.ResultText)End SubEnd Class
依賴屬性
使用 DevExpress.Mvvm.DataAnnotations.DependsonProperties 屬性標(biāo)記依賴屬性。 請注意，與前面得示例不同，下面得代碼僅使用一個(gè)依賴項(xiàng)：“ResultText”取決于兩個(gè)“Operand”屬性，您不能使用此屬性創(chuàng)建鏈?zhǔn)揭蕾図?xiàng)。
C#
public class MultViewModelEx {public virtual int Operand1 { get; set; }public virtual int Operand2 { get; set; }[DependsonProperties("Operand1", "Operand2")]public string ResultText {get { return string.Format("The result is: {0:n0}", Operand1 * Operand2); }}}
VB.NET
Public Class MultViewModelExPublic Overridable Property Operand1() As IntegerPublic Overridable Property Operand2() As Integer<DependsonProperties("Operand1", "Operand2")>Public Readonly Property ResultText() As StringGetReturn String.Format("The result is: {0:n0}", Operand1 * Operand2)End GetEnd PropertyEnd Class
metadata類
在這種方法中，您創(chuàng)建自定義更新方法并使用單獨(dú)得元數(shù)據(jù)類將屬性與這些方法鏈接起來。 如果 BindableProperty 屬性按名稱引用更新方法，則 onPropertyChangedCall 方法使用 lambda 表達(dá)式來檢索方法。 重命名自定義更新方法時(shí)，元數(shù)據(jù)類顯示編譯錯(cuò)誤。
C#
//View Model code[System.ComponentModel.DataAnnotations.metadataType(typeof(metadata))]public class SumViewModel_metaPOCO {public virtual int Operand1 { get; set; }public virtual int Operand2 { get; set; }public virtual int Result { get; set; }public string ResultText {get { return string.Format("The result is: {0:n0}", Result); }}protected void NotifyResultAndResultTextChanged() {Result = Operand1 + Operand2;this.RaisePropertyChanged(x => x.Result);this.RaisePropertyChanged(x => x.ResultText);}//metadata classpublic class metadata: ImetadataProvider<SumViewModel_metaPOCO> {void ImetadataProvider<SumViewModel_metaPOCO>.Buildmetadata(metadataBuilder<SumViewModel_metaPOCO> builder) {builder.Property(x => x.Result).DonotMakeBindable();builder.Property(x => x.Operand1).onPropertyChangedCall(x => x.NotifyResultAndResultTextChanged());builder.Property(x => x.Operand2).onPropertyChangedCall(x => x.NotifyResultAndResultTextChanged());}}}
VB.NET
<System.ComponentModel.DataAnnotations.metadataType(GetType(metadata))>Public Class SumViewModel_metaPOCOPublic Overridable Property Operand1() As IntegerPublic Overridable Property Operand2() As IntegerPublic Overridable Property Result() As IntegerPublic Readonly Property ResultText() As StringGetReturn String.Format("The result is: {0:n0}", Result)End GetEnd PropertyProtected Sub NotifyResultAndResultTextChanged()Result = Operand1 + Operand2Me.RaisePropertyChanged(Function(x) x.Result)Me.RaisePropertyChanged(Function(x) x.ResultText)End Sub'metadata classPublic Class metadataImplements ImetadataProvider(Of SumViewModel_metaPOCO)Private Sub ImetadataProviderGeneric_Buildmetadata(ByVal builder As metadataBuilder(Of SumViewModel_metaPOCO)) Implements ImetadataProvider(Of SumViewModel_metaPOCO).Buildmetadatabuilder.Property(Function(x) x.Result).DonotMakeBindable()builder.Property(Function(x) x.Operand1).onPropertyChangedCall(Function(x) x.NotifyResultAndResultTextChanged())builder.Property(Function(x) x.Operand2).onPropertyChangedCall(Function(x) x.NotifyResultAndResultTextChanged())End SubEnd ClassEnd Class
集合綁定
要使用數(shù)據(jù)源記錄填充多項(xiàng)目控件，請使用 SetItemsSourceBinding 方法。
C#
var fluentApi = mvvmContext1.OfType<ViewModelClass>();fluentApi.SetItemsSourceBinding(TargetItemSelector,SourceSelector,Matchexpression,Createexpression,Disposeexpression,Changeexpression);
VB.NET
Dim fluentApi = mvvmContext1.OfType(Of ViewModelClass)()fluentApi.SetItemsSourceBinding(Target ItemSelector, SourceSelector, Matchexpression, Createexpression, Disposeexpression, Changeexpression)
在 MVVM 可靠些實(shí)踐演示中，以下代碼使用自定義實(shí)體類得對象填充列表框。 SetBinding 方法將感謝器得 SelectedItem 屬性與檢索相應(yīng)實(shí)體對象得 ViewModel SelectedEntity 屬性綁定。
C#
//View codemvvmContext.ViewModelType = typeof(ViewModel);var fluentApi = mvvmContext.OfType<ViewModel>();fluentApi.SetItemsSourceBinding(listBox,lb => lb.Items,x => x.Entities,(item, entity) => object.Equals(item.Value, entity),entity => new ImageListBoxItem(entity),null,(item, entity) => {((ImageListBoxItem)item).Description = entity.Text;});fluentApi.SetBinding(listBox, lb => lb.SelectedValue, x => x.SelectedEntity);//ViewModel codepublic class ViewModel {public virtual Entity SelectedEntity { get; set; }public virtual ObservableCollection<Entity> Entities { get; set;}protected void onSelectedEntityChanged() {//"Remove" is a custom ViewModel method that deletes a selected entitythis.RaiseCanExecuteChanged(x => x.Remove());}protected void onEntitiesChanged() {SelectedEntity = Entities.FirstOrDefault();}}//Model codepublic class Entity {public Entity(int id) {this. = id;this.Text = "Entity " + id.ToString();}public int { get; private set; }public string Text { get; set; }}
VB.NET
'View codemvvmContext.ViewModelType = GetType(ViewModel)Dim fluentApi = mvvmContext.OfType(Of ViewModel)()fluentApi.SetItemsSourceBinding(listBox,Function(lb) lb.Items,Function(x) x.Entities,Function(item, entity) Object.Equals(item.Value, entity),Function(entity) New ImageListBoxItem(entity),Nothing,Function(item, entity) CType(item, ImageListBoxItem).Description = entity.Text)fluentApi.SetBinding(listBox, Function(lb) lb.SelectedValue, Function(x) x.SelectedEntity)'ViewModel codePublic Class ViewModelPublic Overridable Property SelectedEntity() As EntityPublic Overridable Property Entities() As ObservableCollection(Of Entity)Protected Sub onSelectedEntityChanged()'"Remove" is a custom ViewModel method that deletes a selected entityMe.RaiseCanExecuteChanged(Function(x) x.Remove())End SubProtected Sub onEntitiesChanged()SelectedEntity = Entities.FirstOrDefault()End SubEnd Class'Model codePublic Class EntityPublic Sub New(ByVal id As Integer)Me. = idMe.Text = "Entity " & id.ToString()End SubPrivate private As IntegerPublic Property () As IntegerGetReturn privateEnd GetPrivate Set(ByVal value As Integer)private = valueEnd SetEnd PropertyPublic Property Text() As StringEnd Class
觸發(fā)器
觸發(fā)器允許您在 ViewModel 屬性更改時(shí)修改 UI（視圖）。 在 DevExpress 演示中，復(fù)選框綁定到 ViewModel “IsActive”屬性。 當(dāng)此屬性得值更改時(shí)，觸發(fā)器會(huì)更改 UI 元素（標(biāo)簽）得背景顏色。
C#
//ViewModel codepublic class ViewModel {public virtual bool IsActive { get; set; }}//ViewModel codevar fluent = mvvmContext.OfType<ViewModel>();fluent.SetBinding(checkEdit, c => c.Checked, x => x.IsActive);fluent.SetTrigger(x => x.IsActive, (active) => {if(active)label.Appearance.BackColor = Color.LightPink;elselabel.Appearance.BackColor = Color.Empty;});
VB.NET
'ViewModel codePublic Class ViewModelPublic Overridable Property IsActive() As BooleanEnd Class'ViewModel codePrivate fluent = mvvmContext.OfType(Of ViewModel)()fluent.SetBinding(checkEdit, Function(c) c.Checked, Function(x) x.IsActive)fluent.SetTrigger(Function(x) x.IsActive, Sub(active)If active Thenlabel.Appearance.BackColor = Color.LightPinkElselabel.Appearance.BackColor = Color.EmptyEnd IfEnd Sub)
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