How can i Bind the Length of a Textbox to a Textblock?

问题

I need an help to bind some things on wpf. I have this column of textboxes, whitch show the value of a property in the Datagrid.

<DataGridTemplateColumn Header="Value" Width="150">
    <DataGridTemplateColumn.CellTemplate>
        <DataTemplate>               
            <TextBox Width="150" Name="PropertyTextBox" Text="{Binding Path=Property.Value.Value, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" IsEnabled="{Binding Path=Property, Converter={StaticResource isSimpleJPropertyConverter}, Mode=OneWay}" />
        </DataTemplate>
    </DataGridTemplateColumn.CellTemplate>
</DataGridTemplateColumn>

I need to show the actual Length of the textbox in another column, and if i change the text of the textbox the Length must change too.

<DataGridTemplateColumn Header="Leng" Width="150">
<DataGridTemplateColumn.CellTemplate>
    <DataTemplate>
        <TextBlock Width="150" Text="{Binding Path=Text.Length, ElementName=PropertyTextBox, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}" />
    </DataTemplate>
</DataGridTemplateColumn.CellTemplate>

Why this don't work? Any tips? How can i do it?

Edit: full xaml

<Window x:Class="WpfInterceptor.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    x:Name="this"
    xmlns:local="clr-namespace:WpfInterceptor"
    Title="MainWindow" Height="728" Width="755" Loaded="Window_Loaded">
<Window.Resources>

    <!--<local:JPropertyConverter x:Key="jPropertyConverter" />-->
    <local:IsSimpleJPropertyConverter x:Key="isSimpleJPropertyConverter" />
    <local:LengthConverter x:Key="lengthConverter" />

</Window.Resources>
<Grid DataContext="{Binding ElementName=this}">

    <Button x:Name="btn6" Content="Vai a Host" HorizontalAlignment="Left" Margin="662,172,0,0" VerticalAlignment="Top" Width="75" Click="Button_Click_1"/>
    <TextBox x:Name="txt1" HorizontalAlignment="Left" Height="157" Margin="10,10,0,0" TextWrapping="Wrap" Text="TextBox" VerticalAlignment="Top" Width="727"/>
    <RadioButton x:Name="rb2" Content="MID" HorizontalAlignment="Left" Margin="305,175,0,0" VerticalAlignment="Top" Checked="rb2_Checked"/>
    <RadioButton x:Name="rb1" Content="JSON" HorizontalAlignment="Left" Margin="246,175,0,0" VerticalAlignment="Top" Checked="rb1_Checked"/>
    <Button x:Name="btn5" Content="Clear" HorizontalAlignment="Left" Margin="582,172,0,0" VerticalAlignment="Top" Width="75" Click="Button_Click"/>

   <StackPanel>
    <DataGrid x:Name="dg" HorizontalAlignment="Left" Margin="10,199,0,0" VerticalAlignment="Top" Height="46" Width="727" />

        <DataGrid x:Name="dg2" ItemsSource="{Binding Path=Properties}"  AutoGenerateColumns="False" ScrollViewer.VerticalScrollBarVisibility="Visible" ScrollViewer.IsDeferredScrollingEnabled="True" ScrollViewer.CanContentScroll="True" ScrollViewer.HorizontalScrollBarVisibility="Visible" Height="350" IsEnabled="False">
            <DataGrid.Columns>
                <DataGridTextColumn Binding="{Binding Path=NomeCampo}" Header="Nome Campo" IsReadOnly="True" />
                <DataGridTextColumn Binding="{Binding Path=Lunghezza}" Header="Lunghezza" IsReadOnly="True"  Width="50" />

                <DataGridTemplateColumn Header="Valore" Width="150">
                    <DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <Canvas Background="Azure">
                               <!-- <TextBox Name="PropertyTextBox" Text="{Binding Path=Property.Value.Value, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"  /> seconda-->
                                <TextBox Width="150" Name="PropertyTextBox" Text="{Binding Path=Property.Value.Value, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" IsEnabled="{Binding Path=Property, Converter={StaticResource isSimpleJPropertyConverter}, Mode=OneWay}" />
                                <!--<TextBox Width="250"  Text="{Binding Path=Property, Converter={StaticResource jPropertyConverter},  Mode=TwoWay, UpdateSourceTrigger=PropertyChanged , Delay=500}" /> prima versione-->
                            </Canvas>
                        </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                </DataGridTemplateColumn>

                <!--<DataGridTextColumn Header="Lunghezza2" IsReadOnly="True"  Width="50" Binding="{Binding Path=Property.Value.Value.Length, UpdateSourceTrigger=PropertyChanged, Mode=OneWay, Converter={StaticResource lengthConverter}}"  />-->
                <DataGridTextColumn Header="Lunghezza2" IsReadOnly="True" Width="50" Binding="{Binding Path=Lunghezza2, UpdateSourceTrigger=PropertyChanged, Mode=OneWay}" />


                <DataGridTemplateColumn Header="Leng" Width="150">
                    <DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <TextBlock Width="150" Text="{Binding Path=PropertyTextBox.Text.Length, ElementName=PropertyTextBox, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}" />
                        </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                </DataGridTemplateColumn>

            </DataGrid.Columns>
        </DataGrid>

    </StackPanel>

    <Button x:Name="btn2" Content="Mostra Campi" HorizontalAlignment="Left" Margin="90,172,0,0" VerticalAlignment="Top" Width="91" Click="Button_Click_2"/>
    <Button x:Name="btn3" Content="Apri file" HorizontalAlignment="Left" Margin="10,172,0,0" VerticalAlignment="Top" Width="75" Click="Button_Click_3"/>
    <Button x:Name="btn4" Content="Accetta Modifiche" HorizontalAlignment="Left" Margin="406,172,0,0" VerticalAlignment="Top" Width="171" Click="Button_Click_4" IsEnabled="False"/>

</Grid>

回答1:

DataGrid columns are not in same visual tree. Hence you can't bind using ElementName.

Bind with property from your model object because it's already binded TwoWay with TextBox:

<DataTemplate>
    <TextBlock Width="150" Text="{Binding Path=Property.Value.Value.Length}" />
</DataTemplate>

来源：https://stackoverflow.com/questions/28345702/how-can-i-bind-the-length-of-a-textbox-to-a-textblock

标签

wpf

xaml

binding