带有MVVM模式的windows 8手机应用程序，用于textchanged和clickCommand序列

Question

I am facing an issue for wizard kind of screen, user enters text in textbox and clicks on "go to Next Screen", then "go to Next Screen" related command fires prior to "text-changed" of required field and user gets annoyed message to enter data where data is already in textbox but sequence of events firing is making a problem. Can i make sure to fire "text-changed" property first and then click command?

<TextBox  Text="{Binding UserName,Mode=TwoWay}"></TextBox>


public RelayCommand<String> NavigateToCommand
        {
            get
            {
                return _navigateToCommand
                    ?? (_navigateToCommand = new RelayCommand<String>(
                        pw =>
                        {
if (String.IsNullOrWhiteSpace(this.UserName))
            {
                message = "UserName is required ";
            }
}}}

Answer 1

只需更改源触发器。

Text="{Binding UserName,Mode=TwoWay,UpdateSourceTrigger=OnPropertyChanged}"