wpf 找不到 RelayCommand 的引用
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RelayCommand's reference is not found
提问by Lamloumi Afif
I have a WPF application in which i'd like to change its design pattern to MVVM.I have used this snippet
我有一个 WPF 应用程序，我想在其中将其设计模式更改为MVVM.I have used this snippet
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using FirstMVVm.Model;
using System.ComponentModel;
using System.Windows.Input;
using System.Windows;
namespace FirstMVVm.ModelView
{
class MyViewModel: INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private float result;
public float Result
{
get { return result; }
private set
{
if (result != value) {
result = value;
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs("Result"));
}
}
}
}
public int Number { get; set; }
private RelayCommand _calculatePerimeterCommand;
public ICommand CalculatePerimeterCommand
{
get
{
if (_calculatePerimeterCommand == null)
{
_calculatePerimeterCommand = new RelayCommand(param => this.CalculatePerimeter());
}
return _calculatePerimeterCommand;
}
}
private MyModel _model;
public MyViewModel() {
_model = new MyModel();
}
private void CalculatePerimeter(){
Result = _model.Perimetre(Number);
}
}
}
The problem is that the RelayCommandtype is not known and i don't know what is the assembly missing.
问题是RelayCommand类型未知，我不知道缺少什么程序集。
- So how can i fix this problem?
- 那么我该如何解决这个问题呢？
Thanks,
谢谢，
回答by J R B
RelayCommand is a class created by MS for handling event or command in WPF. you can create own class or go through below link.
RelayCommand 是 MS 创建的一个类，用于处理 WPF 中的事件或命令。您可以创建自己的课程或通过以下链接。
回答by Matas Vaitkevicius
This does not necessarily have to be RelayCommandit's simply a name of class from most common example on the web.
这不一定RelayCommand是网络上最常见示例中的类名。
The mechanism of ICommandworks in a way that instead of getter or setter being called you get public void Execute(object parameter)to be called on class that is implementing ICommand
该机制的ICommand工作方式是，不是调用 getter 或 setter，而是public void Execute(object parameter)在正在实现的类上调用ICommand
Let me give you an example:
让我给你举个例子：
I have a hyperlink which when clicked should do some stuff before redirecting person to browser.
我有一个超链接，当点击它时应该在将人重定向到浏览器之前做一些事情。
XAML
XAML
<Hyperlink NavigateUri="https://payments.epdq.co.uk/ncol/prod/backoffice/"
Command="{Binding Path=NavigateToTakePayment}" IsEnabled="{Binding CanTakePayment}">
Launch Payments Portal
</Hyperlink>
now in viewModel I have property
现在在 viewModel 我有财产
public ICommand NavigateToTakePayment
{
get { return _navigateToTakePayment ?? (_navigateToTakePayment = new NavigateToTakePaymentCommand(this)); }
set { _navigateToTakePayment = value; }
}
but when hyperlink is clicked instead of getter being fired like one would expect NavigateToTakePaymentCommandclass Executemethod is fired instead.
但是当点击超链接而不是像人们期望的那样触发 getter 时，会触发NavigateToTakePaymentCommand类Execute方法。
public class NavigateToTakePaymentCommand : ICommand
{
public NavigateToTakePaymentCommand(PaymentViewModel paymentViewModel)
{
ViewModel = paymentViewModel;
}
public PaymentViewModel ViewModel { get; set; }
public bool CanExecute(object parameter)
{
return true;
}
public void Execute(object parameter)
{
//your implementation stuff goes here.
}
public event EventHandler CanExecuteChanged;
}
I hope this example will clarify how the mechanism works and will save you some time.
我希望这个例子能够阐明该机制的工作原理并为您节省一些时间。
