//
// Implementation
//
#region public void BindValue(object sender, PDFDataBindEventArgs args)
/// <summary>
/// Provides a method that can be added to the databind or databound event handlers,
/// and will be called when that component or style is databound.
/// </summary>
/// <param name="sender">The sender of the event (must be a Style or an IPDFStyledComponent</param>
/// <param name="args">The databind args with the context for creating the expression</param>
/// <remarks>
/// This method must be called before the Expression will be used, so the Expression can be built.
/// If it is not called then the instance will fallback to the default base implementation
/// </remarks>
public void BindValue(object sender, PDFDataBindEventArgs args)
{
Style style;
if (sender is Style)
{
style = (sender as Style);
}
else if (sender is IPDFStyledComponent)
{
style = (sender as IPDFStyledComponent).Style;
}
else
{
throw new InvalidCastException("Style values can only be bound on styles or the StyledComponents that own them");
}
var context = args.Context;
if (null == _expression)
{
_expression = CreateExpression(context);
_variableProvider = context.Items.ValueProvider(context.CurrentIndex,
context.DataStack.HasData ? context.DataStack.Current : null);
}
//Execute once to make sure we are all set up - although css variables may not be there.
base.SetValue(this.EvaluateExpression(style));
}
/// <summary>
/// Creates a new style value expression for the style key with the expression and an optional convertor and base value
/// </summary>
/// <param name="key">The style key this expression is assigned for</param>
/// <param name="expressionString">The exppresion to be evaluated at runtime</param>
/// <param name="convertor">An otpional convertor to make the result the required type</param>
/// <param name="baseValue">An optional base value that will be returned before the expression is bound</param>
public StyleValueExpression(PDFStyleKey <T> key, string expressionString, StyleValueConvertor <T> convertor, T baseValue)
: base(key, baseValue)
{
this._expressionString = expressionString ?? throw new ArgumentNullException(nameof(expressionString));
this._convertor = convertor;
this._variableProvider = null;
this._expression = null;
}
