StringFormat and Multibinding with Label

I would like to use StringFormat to do someting like this :

<Label x:Name="myLabel">
    <Label.Content>
        <Multibinding StringFormat="{}{0} - {1}">
            <Binding Path="Lib1" />
            <Binding Path="Lib2" />
        </MultiBinding>
    </Label.Content>
</Label>

However, it's doesn't work and I got this error instead :

>MultiBinding failed because it has no valid Converter. MultiBindingExpression:target element is 'Label' (Name='myLabel'); target property is 'Content' (type 'Object')

Is there any way to make this code work ?

You cant bind this because you are trying to bind a string to an object which wont work because StringFormat requires its target to be a string type. You can get around this by either using a TextBlock instead (which has a Text property) or putting the Textblock as the child of the Label:

<Label x:Name="myLabel">
    <Label.Content>
        <TextBlock>
            <TextBlock.Text>
                <MultiBinding StringFormat="{}{0} - {1}">
                    <Binding Path="Lib1" />
                    <Binding Path="Lib2" />
                 </MultiBinding>
            </TextBlock.Text>
        </TextBlock>
    </Label.Content>
</Label>

For those wondering you can also leave the <Label.Content> tag from Leom Burke's answer. This saves another two lines of code.

<Label x:Name="myLabel">
    <TextBlock>
        <TextBlock.Text>
           <MultiBinding StringFormat="{}{0} - {1}">
               <Binding Path="Lib1" />
               <Binding Path="Lib2" />
            </MultiBinding>
        </TextBlock.Text>
    </TextBlock>
</Label>

<Label>
   <AccessText>
      <MultiBinding StringFormat="{x:Static properties:Resources.MyText}">
         <Binding Path="MyObj.MyProp" Mode="OneTime"/>
      </MultiBinding>
   </AccessText>
</Label>

Where Resources.MyText can hold anything like "Fox jumps over {0}."