問題

如何對(duì)ICommand傳入多個(gè)參數(shù)？

背景

最近在做一個(gè)WPF的開發(fā)，有多個(gè)相近的功能寫了不同的Command，因?yàn)橐獙?duì)應(yīng)不同的對(duì)象。因?yàn)槭荂trlCV，顯得代碼有點(diǎn)冗贅不夠優(yōu)雅，但是ICommand又只能接受一個(gè)參數(shù)。

思路

使用MultiBinding,對(duì)CommandParameter進(jìn)行綁定，然后再使用IMultiValueConverter對(duì)多個(gè)參數(shù)進(jìn)行轉(zhuǎn)換，變成object傳進(jìn)去

代碼實(shí)現(xiàn)

1. 實(shí)現(xiàn)IMultiValueConverter

public class MultiValueConverter:IMultiValueConverter{
    public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
    {
        object[] args = new object[values.Length];
        values.CopyTo(args, 0); 
        //要重新創(chuàng)建values的實(shí)例，否則參數(shù)傳過去是空引用
        return args;
    }

    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

2. 在XAML里實(shí)現(xiàn)綁定

<Page.Resource>
    <cvt:MultiValueConverter x:Key="commandParameterConverter">
</Page.Resource>
...
<Button
    Command="{Binding StartCommand}"
    Content="Start">
    <Button.CommandParameter>
        <MultiBinding Converter="{StaticResource commandParameterConverter}">
            <Binding Path="DataContext.Path1" RelativeSource="{RelativeSource AncestorType=local:HomePage}" />
        </MultiBinding>
    </Button.CommandParameter>
</Button>

3. 在ViewModel中的處理邏輯

public class HomePageViewModel:ObservableObject{
    public string Path1 {get;set;}

    [RelayCommand]
    private async Task Start(object arg){
        if(object is not object[] args || args[0] is not string path){
            throw new Exception("Invalid argument type");
        }

        //Do Something else...
    }
}

4. 亦可以使用Tuple進(jìn)行傳參
   僅展示TupleConverter啦，其余大體差不多

public class TupleConverter:IMultiValueConverter{
     public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
    {
        return Tuple.Create(values[0],values[1],values[2]);
    }

    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}