/// <summary>
/// The ICompilableTypeConverter interface states that the param Expression value must be assignable to TSource
/// </summary>
public Expression GetTypeConverterExpression(Expression param)
{
if (param == null)
{
throw new ArgumentNullException("param");
}
return(Expression.Condition(
Expression.Property(param, _sourceTypeIsInitialisedProperty),
_wrappedConverter.GetTypeConverterExpression(param),
Expression.Constant(default(TDest), typeof(TDest))
));
}
/// <summary>
/// This must return a Linq Expression that retrieves the value from SrcType.Property as TargetType - the specified "param" Expression must have a type that
/// is assignable to SrcType. The resulting Expression will be assigned to a Lambda Expression typed as a TSourceObject to TPropertyAsRetrieved Func.
/// </summary>
public override Expression GetPropertyGetterExpression(Expression param)
{
if (param == null)
{
throw new ArgumentNullException("param");
}
if (typeof(TSourceObject) != param.Type)
{
throw new ArgumentException("param.NodeType must match typeparam TSourceObject");
}
// Get property value (from object of type TSourceObject) without conversion (this will be as type TPropertyOnSource)
// - If value is null, return default TPropertyAsRetrieved (not applicable if a value type)
// - Otherwise, pass through type converter (to translate from TPropertyOnSource to TPropertyAsRetrieved)
var propertyValue = Expression.Property(param, _propertyInfo);
var conversionExpression = _compilableTypeConverter.GetTypeConverterExpression(propertyValue);
if (typeof(TPropertyOnSource).IsValueType)
{
// If it's a value type then it's not possible for it to be null so don't do the below work
return(conversionExpression);
}
if (_compilableTypeConverter.PassNullSourceValuesForProcessing)
{
// If _compilableTypeConverter supports passing null into it, then don't generate the condition that prevents this from happening
return(conversionExpression);
}
return(Expression.Condition(
Expression.Equal(
propertyValue,
Expression.Constant(null)
),
Expression.Constant(default(TPropertyAsRetrieved), typeof(TPropertyAsRetrieved)),
conversionExpression
));
}