CODEWITHSUNDEEP
c#wpfstringbindingconverters
SkonJeet
SkonJeet

Reputation: 4905

Can't get simple converter to work when using on a bound String

I have the following converter defined (C#):

class BodyValueConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        string s = value.ToString();
        int prefixLength;
        if (!int.TryParse(parameter.ToString(), out prefixLength))
            return s;
        return s.Substring(0, prefixLength);
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotSupportedException();
    }
}

This will start at the start of the string being passed and will return the amount of characters I specify as a parameter.

In my XAML I have instanced the converter:

<local:BodyValueConverter x:Key="BodyValueConverter"/>

In attempting to use this converter in a textblock I get an error:

<DataTemplate x:Key="AppointmentTemplate">
    <StackPanel Orientation="Horizontal">
        <TextBlock Text="{Binding Subject}"></TextBlock>
        <TextBlock Text="{Binding Path=Subject, Converter={StaticResource BodyValueConverter}, ConverterParameter=1}"></TextBlock>
    </StackPanel>
</DataTemplate>

The error is:

XAMLParseException: Provide value on 'System.Windows.Markup.StaticResourceHolder' threw an exception.

The first textblock works fine to display subject. The 2nd line is what gives me the exception.

Upvotes: 1

Views: 850

Answers (2)

Rachel
Rachel

Reputation: 132558

What's the order of your objects in your XAML?

The Converter has to be defined prior to actually being used, so be sure your <Converter> is above your <DataTemplate> in your Resources

Another alternative is to switch to using a DynamicResource instead of a StaticResource, since a DynamicResource is evaluated when it is needed, not when the XAML is loaded

Upvotes: 4

scottheckel
scottheckel

Reputation: 9244

That error is usually thrown when it can't find the static resource you are looking for. You'll need to define that in your static resources.

<Window 
  .... snip ...
  xmlns:local="clr-namespace:YourLocalNamespace"
  <Window.Resources>
    <local:BodyValueConverter x:Key="BodyValueConverter"/>
  </Window.Resources>
  .... snip ....
  <DataTemplate x:Key="AppointmentTemplate">
    <StackPanel Orientation="Horizontal">
      <TextBlock Text="{Binding Subject}"></TextBlock>
      <TextBlock Text="{Binding Path=Subject, Converter={StaticResource BodyValueConverter}, ConverterParameter=1}"></TextBlock>
    </StackPanel>
  </DataTemplate>
</Window>

Note: This is when you are defining it in Window. You could define it elsewhere.

If this isn't the issue.... to find a more detailed explanation of what the parse error is... check the inner exception text.

Upvotes: 1

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