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命令触发器
Triggers允许您执行与命令关联的其他查看操作，根据触发Triggers的条件，共有三种触发器类型。
- “Before”触发器 - 允许您在目标命令执行之前执行操作。
C#
mvvmCon = typeof(ViewModelWithSimpleCommand); var fluent = mvvmCon;ViewModelWithSimpleCommand>(); (commandButton, x => x.DoSomething); (x => x.DoSomething) .Before(() => X("The target command is about to be executed"));VB.NET
mvvmCon = GetType(ViewModelWithSimpleCommand) Dim fluent = mvvmCon(Of ViewModelWithSimpleCommand)() (commandButton, Function(x) x.DoSomething) (Sub(x) x.DoSomething) .Before(Function() X("The target command is about to be executed"))- “After”触发器 - 允许您在目标命令完成后执行操作。
C#
mvvmCon = typeof(ViewModelWithSimpleCommand); var fluent = mvvmCon;ViewModelWithSimpleCommand>(); (commandButton, x => x.DoSomething); (x => x.DoSomething) .After(() => X("The target command has been executed"));VB.NET
mvvmCon = GetType(ViewModelWithSimpleCommand) Dim fluent = mvvmCon(Of ViewModelWithSimpleCommand)() (commandButton, Function(x) x.DoSomething) (Function(x) x.DoSomething).After(Function() X("The target command has been executed"))- “CanExecute”条件触发器 - 允许您在目标命令的 CanExecute 条件更改时执行操作。
C#
var fluent = mvvmCon;ViewModelWithSimpleCommandAndCanExecute>(); (commandButton, x => x.DoSomething); // When the CanExecute condition changes, the message shows up (x => x.DoSomething) .OnCanExecuteChanged(() => X("The CanExecute condition has changed"));VB.NET
Dim fluent = mvvmCon(Of ViewModelWithSimpleCommandAndCanExecute)() (commandButton, Function(x) x.DoSomething) ' When the CanExecute condition changes, the message shows up (Function(x) x.DoSomething) .OnCanExecuteChanged(Function() X("The CanExecute condition has changed"))请注意，触发器为绑定到目标命令的每个 UI 元素执行。 单击任何按钮时，下面的代码示例会显示一个消息框。
C#
mvvmCon;BulkEditViewModel>() .WithCommand(vm => vm.RemoveFields()) .Bind(button1) .Bind(button2) .After(() => Me("Test"));VB.NET
mvvmCon(Of BulkEditViewModel)() .WithCommand(Function(vm) vm.RemoveFields()) .Bind(button1) .Bind(button2) .After(Function() Me("Test"))非 POCO 命令
上面描述的 POCO 类命令允许您使用最直接和无故障的语法，DevExpress MVVM 框架还支持其他命令类型 - 以确保旧项目的轻松迁移。
DevExpress 委托命令对象
委托命令是 Sy 接口的实现。
运行demo: Simple Commands
C#
DelegateCommand command = new DelegateCommand(() => { X("Hello!"); }); commandBu(command);VB.NET
Dim command As New DelegateCommand(Sub() X("Hello!")) commandBu(command)运行demo:Commands with CanExecute Conditions
C#
Func<bool> canExecute = () => (2 + 2 == 4); DelegateCommand command = new DelegateCommand(() => { X("Hello!"); }, canExecute); commandBu(command);VB.NET
Dim canExecute As Func(Of Boolean) = Function() (2 + 2 = 4) Dim command As New DelegateCommand(Sub() X("Hello!"), canExecute) commandBu(command)运行demo:Commands with Parameters
C#
DelegateCommand<object> command = new DelegateCommand<object>((v) => { X("The parameter is {0}.", v)); }); object parameter = 5; commandBu(command, () => parameter);VB.NET
Dim command As New DelegateCommand(Of Object)(Sub(v) X("The parameter is {0}.", v))) Dim parameter As Object = 5 commandBu(command, Function() parameter)运行demo:Commands with Parameterized CanExecute Conditions
C#
Func<int, bool> canExecute = (p) => (2 + 2 == p); DelegateCommand<int> command = new DelegateCommand<int>((v) => { X("The parameter is {0}.", v)); }, canExecute); int parameter = 4; commandBu(command, () => parameter);VB.NET
Dim canExecute As Func(Of Integer, Boolean) = Function(p) (2 + 2 = p) Dim command As New DelegateCommand(Of Integer)(Sub(v) X("The parameter is {0}.", v)), canExecute) Dim parameter As Integer = 4 commandBu(command, Function() parameter)自定义命令类
这些是具有至少一个 Execute 方法的任何自定义类型的对象。 如果需要，您可以添加 CanExecute 方法和 CanExecuteChanged 事件。
运行demo:Simple Commands
C#
CommandObject command = new CommandObject(); commandBu(command); public class CommandObject { public void Execute(object parameter) { X("Hello!"); } }VB.NET
Private command As New CommandObject() commandBu(command) Public Class CommandObject Public Sub Execute(ByVal parameter As Object) X("Hello!") End Sub End Class运行demo:Commands with Parameters
C#
CommandObjectWithParameter command = new CommandObjectWithParameter(); int parameter = 4; commandBu(command, () => parameter); public class CommandObjectWithParameter { public void Execute(object parameter) { X( "The parameter is {0}.", parameter)); } public bool CanExecute(object parameter) { return object.Equals(2 + 2, parameter); } }VB.NET
Dim command As New CommandObjectWithParameter() Dim parameter As Integer = 4 commandBu(command, Sub() parameter) Public Class CommandObjectWithParameter Public Sub Execute(ByVal parameter As Object) X("The parameter is {0}.", parameter)) End Sub Public Function CanExecute(ByVal parameter As Object) As Boolean Return Object.Equals(2 + 2, parameter) End Function End ClassDevExpress WinForm
DevExpress WinForm拥有180+组件和UI库，能为Windows Forms平台创建具有影响力的业务解决方案。DevExpress WinForms能完美构建流畅、美观且易于使用的应用程序，无论是Office风格的界面，还是分析处理大批量的业务数据，它都能轻松胜任！