动态linq和运算符重载

Question

Consider the code below:

var vectorTest = new Vector2(1, 2) + new Vector2(3, 4); // Works

var x = Expression.Parameter(typeof(Vector2), "x");
var test = System.Linq.Dynamic
                 .DynamicExpression.ParseLambda(new[] { x }, null, "x = x + x");

Running it, I get the exception below:

System.Linq.Dynamic.ParseException was unhandled by user code Message=Operator '+' incompatible with operand types 'Vector2' and 'Vector2' Source=DynamicLINQ Position=6

How do I get the parser to 'see' the + operator overload on the Vector2 type?

EDIT: I also get the same issue with the = operator.
Looking at the source I can see why, it looks at a special interface that lists loads of methods, for simple types and if it can't find it, then it raises the exception. Trouble is, my type ( Vector2 ) isn't in that list, so it won't ever find the operator methods.

Answer 1

Working with the DynamicLinq library, you'll need to add the signature to one of the signature interfaces found in the System.Linq.Dynamic.ExpressionParser . It will only parse operations it recognizes.

It seems it will look at all the private interfaces found in ExpressionParser . Just add an interface within the ExpressionParser and it seems to suppress the error.

interface ICustomSignatures
{
    void F(Microsoft.Xna.Framework.Vector2 x, Microsoft.Xna.Framework.Vector2 y);
}

Just to be safe (and possibly fit the intended pattern), it might be safer to add to/extend from the IAddSignatures interface.

interface ICustomSignatures : IAddSignatures
{
    void F(Microsoft.Xna.Framework.Vector2 x, Microsoft.Xna.Framework.Vector2 y);
}