WPF StringFormat on Label Content

bindingwpfwpf-controlswpfdatagridwpftoolkit

I want to format my string binding as Amount is X where X is a property bound to a label.

I've seen many examples but the following doesn't work:

<Label Content="{Binding Path=MaxLevelofInvestment, 
   StringFormat='Amount is {0}'}" />

I've also tried these combinations:

StringFormat=Amount is {0}
StringFormat='Amount is {}{0}'
StringFormat='Amount is \{0\}'

I even tried changing the binding property's datatype to int, stringand double. Nothing seems to work. This is a very common use case but doesn't seem to be supported.

Best Answer

The reason this doesn't work is that the Label.Content property is of type Object, and Binding.StringFormat is only used when binding to a property of type String.

What is happening is:

  1. The Binding is boxing your MaxLevelOfInvestment value and storing it the Label.Content property as a boxed decimal value.
  2. The Label control has a template that includes a ContentPresenter.
  3. Since ContentTemplate is not set, ContentPresenter looks for a DataTemplate defined for the Decimal type. When it finds none, it uses a default template.
  4. The default template used by the ContentPresenter presents strings by using the label's ContentStringFormat property.

Two solutions are possible:

  • Use Label.ContentStringFormat instead of Binding.StringFormat, or
  • Use a String property such as TextBlock.Text instead of Label.Content

Here is how to use Label.ContentStringFormat:

<Label Content="{Binding Path=MaxLevelofInvestment}" ContentStringFormat="Amount is {0}" />

Here is how to use a TextBlock:

<TextBlock Text="{Binding Path=MaxLevelofInvestment, StringFormat='Amount is {0}'}" />

Note: For simplicity I omitted one detail in the above explanation: The ContentPresenter actually uses its own Template and StringFormat properties, but during loading these are automatically template-bound to the ContentTemplate and ContentStringFormat properties of the Label, so it seems as if the ContentPresenter is actually using the Label's properties.

Related Topic