C# WPF.Net4.8 框架只读TextBox文本绑定延迟更新

Question

I have a string "ConnectionStatus" which is bound to a textbox text property

    private string connectionStatus;
    public string ConnectionStatus
    {
        get
        {
            return connectionStatus;
        }

        set
        {
            if (connectionStatus != value)
            {
                connectionStatus = value;
                NotifyPropertyChanged("ConnectionStatus");
            }
        }
    }

I have a button connected to a RelayCommand:

    void ConnectCmd(object parameter)
    {
        ConnectionStatus = "Connecting..";

        // Do some stuff

        ConnectionStatus = "Connected"
    }

XML

   <TextBox x:Name="TextBlock_ConectedToName" 
               Grid.Column="1"
               Grid.Row="0"
               Grid.ColumnSpan="2"
               Height="40" 
               Margin="5" 
               FontSize="26"
               IsReadOnly="True"
               HorizontalContentAlignment="Center" 
               VerticalContentAlignment="Center" 
               Text="{Binding ConnectionStatus, 
                              UpdateSourceTrigger=PropertyChanged}" />

 

When the button is pressed, the Relay Command is called, which then updates the string "ConnectionStaus" to "Connecting...", I then do some processing, opening a serial port, and change ConnectionStatus to "Connected" if successful. However, the "Connecting..." text is never displayed, The text updating only seems to trigger when the RelayCommand function finishes. How do I get the text to update immediately.

Answer 1

You're running your code in that relaycommand on the default ui thread. The UI updates on the UI thread. It can only do one thing at once.

You could make your relaycommand async and free up the ui thread momentarily. using.

await Task.Delay(20);

Don't forget to put async in your relaycommand or use an implementation does that for you.