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Validate control usage

The controls in DotVVM can validate whether they are being used correctly. Simple checks can be done by using the MarkupOptions attribute, more complex validation logic is implemented in the ValidateUsage static method in the control code.

MarkupOptions attribute

The MarkupOptions attribute can be applied on DotVVM control properties and has several parameters which control how the property can be used:

  • Required indicates that the property must be set in the markup.
  • AllowBinding indicates that the property can be bound-to on the client-side using value binding.
  • AllowHardCodedValue indicates that the property can specify a value directly in the markup. This option also allows the resource binding which is not a client-side binding and is evaluated on the server.

ValidateUsage method

When some combination of control properties is not supported by a control, you can implement the necessary checks in a specific way in order to detect all errors on Status Page (API) and in the Visual Studio extension.

In the example below, we check whether control has either the Icon or Text property set.

[ControlUsageValidator]
public static IEnumerable<ControlUsageError> ValidateUsage(ResolvedControl control)
{
    //Control usage checks
    if (!control.HasProperty(IconProperty) && !control.HasProperty(TextProperty))
    {
        yield return new ControlUsageError("Button requires Icon, Text or both properties set.", control.DothtmlNode);
    }
}

See also