/// <summary>
/// Helper method for generating a MetaObject which calls a
/// specific method on Dynamic that returns a result
/// </summary>
private DynamicMetaObject CallMethodWithResult(
string methodName,
DynamicMetaObjectBinder binder,
IEnumerable <Expression> args,
Fallback fallback,
Fallback?fallbackInvoke = null
)
{
//
// First, call fallback to do default binding
// This produces either an error or a call to a .NET member
//
DynamicMetaObject fallbackResult = fallback(null);
return(BuildCallMethodWithResult(
methodName,
binder,
args,
fallbackResult,
fallbackInvoke
));
}
private DynamicMetaObject BuildCallMethodWithResult(string methodName, DynamicMetaObjectBinder binder, IEnumerable <Expression> args, DynamicMetaObject fallbackResult, Fallback?fallbackInvoke)
{
//
// Build a new expression like:
// {
// object result;
// TryGetMember(payload, out result) ? fallbackInvoke(result) : fallbackResult
// }
//
ParameterExpression result = Expression.Parameter(typeof(object), null);
IList <Expression> callArgs = new List <Expression>();
callArgs.Add(Expression.Convert(Expression, typeof(T)));
callArgs.Add(Constant(binder));
callArgs.AddRange(args);
callArgs.Add(result);
DynamicMetaObject resultMetaObject = new DynamicMetaObject(result, BindingRestrictions.Empty);
// Need to add a conversion if calling TryConvert
if (binder.ReturnType != typeof(object))
{
UnaryExpression convert = Expression.Convert(resultMetaObject.Expression, binder.ReturnType);
// will always be a cast or unbox
resultMetaObject = new DynamicMetaObject(convert, resultMetaObject.Restrictions);
}
if (fallbackInvoke != null)
{
resultMetaObject = fallbackInvoke(resultMetaObject);
}
DynamicMetaObject callDynamic = new DynamicMetaObject(
Expression.Block(
new[] { result },
Expression.Condition(
Expression.Call(
Expression.Constant(_proxy),
typeof(DynamicProxy <T>).GetMethod(methodName),
callArgs
),
resultMetaObject.Expression,
fallbackResult.Expression,
binder.ReturnType
)
),
GetRestrictions().Merge(resultMetaObject.Restrictions).Merge(fallbackResult.Restrictions)
);
return(callDynamic);
}