手动修改或清除文本时，RichTextBox绑定断开 [英] RichTextBox Binding is broken when text is manually modified or cleared

问题描述

我有一个绑定到字符串的RichTextBox.

I have a RichTextBox bound to a string.

使用C#生成一个写入其中的字符串.

Using C# I generate a string that writes to it.

但是，如果我想通过单击RichTextBox并使用Backspace键将其删除，或者按Enter来换行来手动更改文本，则绑定会断开，并且我无法再用字符串第二次.

But if I want to manually change the text by clicking into the RichTextBox and deleting it with the backspace key, or pressing Enter to make a new line, the binding becomes broken and I can no longer programmatically write to it with the string a second time.

XAML

<RichTextBox x:Name="rtbScriptView" 
             Margin="11,71,280,56" 
             Padding="10,10,10,48"
             FontSize="14" 
             Grid.ColumnSpan="1" 
             VerticalScrollBarVisibility="Auto" 
             RenderOptions.ClearTypeHint="Enabled"
             Style="{DynamicResource RichTextBoxStyle}">
    <FlowDocument>
        <Paragraph>
            <Run Text="{Binding ScriptView_Text, 
                                Mode=TwoWay, 
                                UpdateSourceTrigger=PropertyChanged}" />
        </Paragraph>
    </FlowDocument>
</RichTextBox>

查看模型

private string _ScriptView_Text;
public string ScriptView_Text
{
    get { return _ScriptView_Text; }
    set
    {
        if (_ScriptView_Text == value)
        {
            return;
        }

        _ScriptView_Text = value;
        OnPropertyChanged("ScriptView_Text");
    }
}

C#

ViewModel vm = new ViewModel();
DataContext = vm;

// Display a string in the RichTextBox

vm.ScriptView_Text = "This is a test."; // <-- This won't work if text is manually modified

推荐答案

编辑RichTextBox时，将更改FlowDocument元素内部的元素.绑定的元素可能会在此编辑过程中的某个时候被删除. 看看RichtTextBox.Document.Groups，看看编辑RichTextBox时发生了什么.

When you edit the RichTextBox, you alter the elements inside of the FlowDocument element. The element you have a binding on, is probably removed at some point during this editing. Have a look at RichtTextBox.Document.Groups to see what's happening when you edit the RichTextBox.

默认的RichTextBox不能很好地支持MVVM/Binding.您希望在Document属性上具有一个绑定，但是默认的RichTextBox不支持此绑定. 您可以此处.

The default RichTextBox does not really support MVVM/Binding very well. You'd want to have a binding on the Document property, but this is not supported for the default RichTextBox. You could have a look here.

还是自己扩展它，像这样?

Or extend it yourself, something like this?:

BindableRichTextBox类

public class BindableRichTextBox : RichTextBox
{
    public static readonly DependencyProperty DocumentProperty = DependencyProperty.Register(nameof(Document), typeof(FlowDocument), typeof(BindableRichTextBox), new FrameworkPropertyMetadata(null, OnDocumentChanged));

    public new FlowDocument Document
    {
        get => (FlowDocument)GetValue(DocumentProperty);
        set => SetValue(DocumentProperty, value);
    }

    public static void OnDocumentChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args)
    {
        var rtb = (RichTextBox)obj;
        rtb.Document = args.NewValue != null ? (FlowDocument)args.NewValue : new FlowDocument();
    }   
}

XAML

<controls:BindableRichTextBox Document="{Binding YourFlowDocumentObject, Mode=OneWay}"/>

然后您可以从FlowDocument中获取字符串.

Then you can get the string from the FlowDocument.

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