WPF TextBox and Scroll behavior

问题

I have a problem. I need to host grid with controls in ScrollViewer to prevent textbox from being either truncated or collapsed to zero-with at the UI. Also I want the with of textbox to be expanded when user change windows width. I'm setting Window's content to following code

<DockPanel>
    <TreeView DockPanel.Dock="Left" Width="150"/>
    <ScrollViewer VerticalScrollBarVisibility="Auto" HorizontalScrollBarVisibility="Auto">
        <Grid>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="Auto"/>
                <ColumnDefinition />
            </Grid.ColumnDefinitions>
            <Grid.RowDefinitions>
                <RowDefinition Height="Auto"/>
            </Grid.RowDefinitions>
            <TextBlock Text="Name" 
                       Margin="5" 
                       VerticalAlignment="Center"/>
            <TextBox Grid.Column="1"
                     Text="Some Name"
                     Margin="5"
                     VerticalAlignment="Center"
                     MinWidth="200"/>
        </Grid>
    </ScrollViewer>
</DockPanel>

All work fine, but when user types very long text in TextBox it is being expanded and horizontal scroll appears. Is there any easy way to limit TextBox maximum width and allow it to be expanded only when user changes window size.

回答1:

The problem is that the parent elements are providing TextBox with as much space as it thinks it needs, and when more text is present it will expand instead of staying at the initial automatic size.

One solution here is to make another auto-sized element and bind the TextBox.Width to it:

<DockPanel>
    <TreeView Width="150" DockPanel.Dock="Left"/>
    <ScrollViewer HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto">
        <Grid>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="Auto"/>
                <ColumnDefinition/>
            </Grid.ColumnDefinitions>
            <Grid.RowDefinitions>
                <RowDefinition Height="Auto"/>
            </Grid.RowDefinitions>
            <TextBlock Margin="5" VerticalAlignment="Center" Text="Name"/>
            <Border x:Name="b" Grid.Column="1" Margin="5"/>
            <TextBox Width="{Binding ActualWidth, ElementName=b}"
                     MinWidth="200"
                     Grid.Column="1"
                     Margin="5"
                     VerticalAlignment="Center"
                     Text="Some Name"/>
        </Grid>
    </ScrollViewer>
</DockPanel>

Note that we set the Margin property of the auto-sizing element (the Border). This is important because if it's not set, there will be a loop:

Border width autosizes to Grid column width
TextBox width resizes to Border.ActualWidth
Grid column width resizes to TextBox width + TextBox margin
Border width autosizes to Grid column width again

By setting the Margin to the same as the TextBox, the resizing of the TextBox won't affect the Grid size.

回答2:

Overriding TextBox.MeasureOverride like so worked for me:

protected override Size MeasureOverride(Size constraint)
{
    Size origSize = base.MeasureOverride(constraint);
    origSize.Width = MinWidth;
    return origSize;
}

回答3:

no - this is a well known problem of wpf and is expected to be fixed in the next release. thanks

来源：https://stackoverflow.com/questions/386039/wpf-textbox-and-scroll-behavior

标签

wpf

controls

panels