Give TextBlock Default Value if result returns null

问题

Hello I am trying to give a default value to a textblock if the results returned are null

Here is what I am trying!

All that returns is the String Format I set!

 <TextBlock x:Name="NameTxtBlock" Grid.Column="0" Margin="0,0,40,0" FontFamily="Segoe UI" FontSize="14" Text="{Binding Name, StringFormat='Item Name: {0}'}"  Padding="2">
    <TextBlock.Style>
        <Style TargetType="TextBlock" >                                            
            <Style.Triggers>
                <DataTrigger Binding="{Binding ElementName=NameTxtBlock, Path=Text}" Value="{x:Null}">
                    <Setter Property="FontStyle" Value="Italic"/>
                    <Setter Property="Text" Value="No Name Found" />
                </DataTrigger>
                <DataTrigger Binding="{Binding ElementName=NameTxtBlock, Path=Text}" Value="{x:Static System:String.Empty}">
                    <Setter Property="FontStyle" Value="Italic"/>
                    <Setter Property="Text" Value="No Name Found" />
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </TextBlock.Style>
</TextBlock>

回答1:

You could use TargetNullValue Property. This will return TargetNullValue without StringFormat if the binding returns Null.

<TextBlock Text="{Binding Name, StringFormat='Item Name: {0}', TargetNullValue='No Name Found'}" />

回答2:

You can use the TargetNullValue property directly in a binding.

<TextBox Text='{Binding Path=LastName, TargetNullValue="No name found."}' />

回答3:

I would bind the TextBlock to a property of an object that didn't return null; make your property return a default value. It appears that you always want the FontStyle to be Italic, so I would just build that in outside the Triggers.

回答4:

In my applications, I find it more reliable to bind my triggers to the actual object my control is bound to. So, if I am looking at Name in the VM for binding of the actual text, I would bind my data trigger to that as well.

<TextBlock x:Name="NameTxtBlock" Grid.Column="0" Margin="0,0,40,0" FontFamily="Segoe UI" FontSize="14" Text="{Binding Name, StringFormat='Item Name: {0}'}"  Padding="2">
<TextBlock.Style>
    <Style TargetType="TextBlock" >                                            
        <Style.Triggers>
            <DataTrigger Binding="{Binding Name}" Value="{x:Null}">
                <Setter Property="FontStyle" Value="Italic"/>
                <Setter Property="Text" Value="No Name Found" />
            </DataTrigger>
            <DataTrigger Binding="{Binding Name}" Value="">
                <Setter Property="FontStyle" Value="Italic"/>
                <Setter Property="Text" Value="No Name Found" />
            </DataTrigger>
        </Style.Triggers>
    </Style>
</TextBlock.Style>

来源：https://stackoverflow.com/questions/16612622/give-textblock-default-value-if-result-returns-null

标签

wpf

xaml

textblock