How to access property attributes on a data bound property in Silverlight?

Question

For example, I have a simple textbox bound to a property:

<TextBox Text="{Binding  FirstName, Mode=TwoWay, ValidatesOnExceptions=True, NotifyOnValidationError=True}" />

The property looks something like this:

[Display(Name="Last Name")]
public string LastName { ... }

So, given the textbox, I would like to get the Display Name property from the attribute. This will be used in a composite control that includes a fieldlabel and some other niceties.

Thanks in advance.

Answer 1

I am not able to attempt this at the moment so this may not be accurate or even possible. As soon as I get to a computer that I can try this I will...until then, this is just theory.

I'm guessing in your composite control you'll have something like this for each data bound field:

<TextBlock Text="{Binding FirstName, Mode=OneWay}" />
<TextBox Text="{Binding FirstName, Mode=TwoWay, ...}" />

What you'll probably need to do in order to create a converter that will look at the binding data for the Display attribute, and convert the value to the attribute value instead. This would cause the above block to look like this:

<TextBlock Text="{Binding FirstName, Mode=OneWay, Converter={StaticResource AttributeConverter}, ConverterParameter=Display}" />
<TextBox Text="{Binding FirstName, Mode=TwoWay, ...}" />

Here I passed in the Display as the parameter in case you wanted to access a different attribute.

Again this is just theory since I'm not able to currently test this and cannot recall if IValueConverter.Convert(object value, ...) passes the object in question or just the string value in this case. If it's just the string value, it probably isn't possible, though if it's the object instead, it will depend on how much access you have to the reflection namespace to evaluate the attributes.

As soon as I am able to, I'll throw the scenario together and try it out.

EDIT:

For some reason the sytax highlighter is giving me the finger when I try to paste code in this edit

Anyways, after trying this out in a little project, it don't think you can do this.

Based on my suggestion of making 2 data bound controls and using a converter for the one that consumes the attribute, I did the following:

1. Created the xaml for the databound control.
2. Create the Custom Attribute for testing
3. Created the Model with the decorated property for testing.
4. Created the converter to attempt to read the attribute from the property.

Here's where I got caught up. I wasn't able to obtain the data bound type from the IValueConverter.Convert(...) method. The value parameter came through as String as did the targetType parameter. While that was the primary hangup, the second was that I was unable to dynamically identify the property name that the control was data bound to. This could be remedied through a converter parameter possibly.

Now, I WAS able to read the attribute value if I supplied the type of my test Model with the decorated property so that much is possible but I wasn't able to dynamically identify the type on the fly.

The only other way I can think of is create some form of observer or converter prior to the data truly being bound to your custom control.

Good Luck